Artificial Trees, Secular Greetings, And Holiday Heart Attacks: Some Answers To Your Christmas Queries (Skeptical Inquirer)

5 minute read

Does the greeting “Happy Holidays” have its roots in secularism?

While it’s commonly considered a secular and more inclusive alternative to Merry Christmas, the term Happy Holidays actually has Christian origins!

Is it more environmentally friendly to get a real or fake Christmas tree?

For those who put up Christmas trees, before questions such as “tinsel or ribbon?” and “angel or star?” can be answered, a much more fundamental query must be asked: real tree or artificial?

Do the holidays cause heart attacks?

The holidays are a time for eating, drinking, and merriment, but could these festive times also be causing a myriad of myocardial infarctions?

Read the answers to all these questions by clicking here: https://skepticalinquirer.org/exclusive/artificial-trees-secular-greetings-and-holiday-heart-attacks-some-answers-to-your-christmas-queries/

An Asthma Attack Caused by a Thunderstorm (McGill OSS)

1 minute read

On November 21st, 2016 a thunderstorm swept across Melbourne, Australia. It brought with it the usual flooded basements, wet shoes and ruined picnics, but it also brought a strange outbreak of asthma. Asthmatics and non-asthmatics alike suddenly found themselves unable to catch their breath, coughing and in extreme cases not being able to breathe at all. By the time the storm had passed, there was a 672% increase in respiratory-related presentations to emergency departments and a 992% increase in asthma-related admissions to hospital. The storm contributed to the death of at least 10 people.

So what was it about this thunderstorm that spurred a city-wide asthma attack? Experts aren’t certain, but the best guess is pollen. It seems that polled, mould and other allergens can get picked up into a storm, riding on wind currents, and carried into the clouds. Up in the sky, they make contact with water molecules, which causes these allergens to break apart into microscopic particles that can more readily enter human lungs and cause reactions. 
In the case of Melbourne, the allergen of importance seems to be from ryegrass. A grain of ryegrass pollen can be broken down into 700 starch granules, measuring 0.6 to 2.5 μm, which may then be inhaled into the deepest parts of the lungs, and cause an asthma attack or an allergic reaction.

As roughly 20% of the world is sensitive to grass or tree pollens, you can imagine that these storms are quite bothersome to many. Melbourne wasn’t the first case of casualties due to storm inflicted asthma, and it sadly will probably not be the last. 

Article originally posted here: https://www.mcgill.ca/oss/article/did-you-know-health/thunderstorms-cause-asthma-attacks

Will Wearing A Hat Make Me Go Bald? (Skeptical Inquirer)

10 minute read

While losing the hair on our heads doesn’t have any serious medical implications on its own, it can be seriously damaging to our psyches. Studies have shown that both women and men with alopecia, or hair loss, experience increased stress, diminished self-esteem, and other negative psychological effects.

Some of us live in fear of our part widening or our hairlines receding. Others have made peace with their eventual journey to becoming a Patrick Stewart lookalike. Either way, you’ve likely heard a lot of unsubstantiated claims about behaviors that can cause baldness. As usual, some can be dismissed outright (no, masturbating won’t make you go bald), but some bear further investigation.

Read the entire article here: https://skepticalinquirer.org/exclusive/will-wearing-a-hat-make-me-go-bald/

Human-Guided Evolution Closer Than You Think (Skeptical Inquirer)

9 minute read

Evolution is often thought of as a solely long-term process. But the conception that its effects are only seen after millions of years ignores a crucial part of the evolutionary process: adaptation. Because we tend to fixate on the drastic changes caused by evolution over huge timescales, it’s easy to ignore the small variations between generations that add together over time to form the big evolutionary changes we focus on. This unintentional side-lining of small adaptations can blind us to the ways in which humans are directly affecting the evolutionary processes of nature. From tuskless elephants to fish that can’t smell, animals are developing specialized adaptations to allow them to live in ecosystems that have been disrupted and altered by mankind. These adaptations are one step in the evolutionary process that already bears the unmistakable marks of humanity’s influence.

Just as humans are changing the planet, they’re changing the fauna that inhabit it. Here are some examples of how.

You can read the entire article here: https://skepticalinquirer.org/exclusive/human-guided-evolution-closer-than-you-think/

Static Shocks Are a Seasonal Occurrence, but Science Can Help Us Avoid Them

5 minute read
Originally posted here: https://mcgill.ca/oss/article/environment-general-science/how-can-i-stop-getting-static-shocks

If you live in Canada, you know what a nightmare winter can be for your hair. No, not because of hat hair, (or at least not entirely because of hat hair), but because of static electricity! All those big scarves and wool hats really do a number on the frizziness of our hair. But even if you’re bald you’ve probably noticed that the number of times you get shocked when reaching for everyday items, like keys, doorknobs and shopping carts, increases in the winter too. There’s some interesting science behind these seasonal shocking scenes, and how you can stop them. 

The number one factor influencing how many zaps you get is humidity. But to understand why we need to review a bit about electricity.  When two objects made of different materials come in contact with each other, like your hair and a hat, for example, electrons can transfer between them. The more prolonged contact, the more electrons move, creating an imbalance of charges between your hair and the hat.

Whether the electrons move from your hair to the hat, or vice-versa, depends on something called the triboelectric series. It’s basically a ranking of different materials based on their tendency to lose or gain electrons. Some things, like rubber or acrylic, are very likely to gain electrons and become negatively charged. Whereas other things, like hair, glass or wool, are more likely to lose electrons and become positively charged. In the case of your hair and a wool hat, since human hair is higher on the triboelectric series, the electrons flow from your hair to the toque.

The problem is that same charges repel each other, so now that your hair is full of positive charge, it’s rather unstable. That’s why, when you get near something conductive, like a metal doorknob, electrons from the knob will “jump” to your hair to neutralize the charge, shocking you in the process. It’s also why your hair stands on end when statically charged. The strands are repelling each other!

Why do charges build up in our hair or clothes, but not in other materials? Because insulating materials, like plastic, fabric or glass, will hold charges quite well, while conducting materials, like metals, will not.

Water happens to be an excellent conductor, so in the spring, summer and fall, when the air in Canada holds a lot of moisture, any negative charges built up on your body can jump to the air (or from the air to your body, either way results in a shock) whenever they want. We don’t even notice these numerous small jumps. But in the winter the air is drier, so the charges simply sit on your skin, waiting for you to approach another conductor (like your car or your girlfriend) to leap to freedom.

Read this to hear about why winter air, especially indoors, is so dry!

When thinking of how wet or dry the air is, we tend to only consider humidity. But there’s another metric that’s important: dew point. The dew point is the temperature at which the air is totally saturated with water. When temperatures fall below the dew point, water condenses on solid surfaces, forming dew in the summer, or frost in the winter (hence why the dew point can also be called the frost point). Warmer air can hold more moisture, meaning that when temperatures are low, the dew point and the actual temperature are quite close. Conversely, when temperatures are high, the dew point and actual temperature are far apart.

Why does dew point matter? Because temperature, dew point, and relative humidity (that % you see on your weather app) are closely linked.

As an example, as I’m writing this, the temperature outside is -9 ˚C, and the relative humidity is 57%. Using the chart below, or less confusingly, this online calculator, we can find that the dew point is -16 ˚C. This tells us that if we go outside it won’t feel muggy because the temperature is significantly above the dew point and the air isn’t saturated with water.

However, our furnaces bring that air into our homes and heat it. This doesn’t change the dew point, but it does change the temperature and the relative humidity. What was a relative humidity of 57% at -16 ˚C becomes a relative humidity of only 7% at 20 ˚C. That’s some really dry air.

Now importantly, the only thing changing here is the relative humidity. The absolute humidity is the same since the furnace doesn’t add or remove any moisture when it heats the air. So even though the air inside and outside is equally dry, it feels much dryer inside due to the relative nature of relative humidity. 

Source: https://www.ncbi.nlm.nih.gov/books/NBK143947/

One of the easiest ways to counteract the shocks that come with these Saharan conditions is to run a humidifier. Increasing the relative humidity of your home will allow more charges to dissipate into the air and avoid the shocks that come with letting them build up.  Side note: If you think desert-like is a bit too harsh to describe the indoor conditions in the Canadian winter, think again. The average relative humidity of the Mojave Desert is 28%, a full 21% higher than my house right now. No wonder I have chapped lips. 

If a humidifier isn’t cutting it for you, you could also try swapping out your rubber-soled slippers for ones with leather soles. Since leather is a better conductor than rubber, this will prevent charges from building up to the same degree. Similarly, try to surround yourself with more cotton. As it falls in the middle of the triboelectric series, it doesn’t have much of a tendency to gain or lose electrons, so won’t build charges like wool or fur.  

Still really worried about static shocks? You could always purposefully discharge yourself every once in a while. If you carry a metal object like a coin, key or paper clip around with you, and touch it to something metal in your house, any electrons stuck to your body will flow through the metal and away, preventing the “jumping” effect that causes a shock. 

Last, but not least, you can always rely on anti-static products to take the charge out of your hair and clothes. Dryer sheets contain chemicals like dipalmitoylethyl hydroxyethylmonium methosulfate that release positively charged ions when heated to neutralize the negatively charged electrons on your clothes. You can even rub your hair gently with one to remove static! Anti-static sprays and anti-static guns can also be used to keep static to a minimum wherever you need to, from your favourite dress to your Rubber Soul vinyl. 

Source: http://www.saapedia.org/en/saa/?type=detail&id=4070

Is hard water dangerous to drink?

3 minute read
Originally posted here: https://mcgill.ca/oss/article/health-you-asked/you-asked-hard-water-dangerous-drink

What is Hard Water?

Hard water is water containing high concentrations of dissolved minerals, usually calcium or magnesium carbonates (CaCO­or MgCO3), chlorides (CaCl2or MgCl2) or sulphates (CaSO4or MgSO4). The hardness of water depends on its source. Groundwater that has been in contact with porous rocks containing deposits of minerals like limestone or dolomite will be very hard, while water from glaciers or flowing through igneous rocks is much softer.

The hardness of water is determined by the milligrams of calcium carbonateper litre and is reported it in parts-per-million (ppm). In general, water with less than 60 ppm can be considered soft, water with 60-120 ppm moderately hard, and water with greater than 120 ppm hard. For reference, Montreal’s water is typically around 116 ppm, or moderately hard, and sea water’s hardness is approximately 6,630 ppm since it contains many dissolved salts (depending on the sea, of course).

Hard water can interfere with the action of soaps and detergents and can result in deposits of calcium carbonate, calcium sulphate and magnesium hydroxide (Mg(OH)2) inside pipes and boilers, causing lower water flows and making for less efficient heating. The ions in hard water can also corrode metal pipes through galvanic corrosion. Water softening filters can circumvent these problems through the use of ion-exchange resins that replace calcium and magnesium ions with sodium and potassium ions. But if one consumes water with higher-than-average concentrations of calcium and magnesium. Is that OK?

The Health Effects of Hard Water

Studies have generally found hard water to have positive effects on the health of its drinkers. Several studies have reported that calcium and magnesium in drinking water have a dose-dependent protective effect when it comes to cardiovascular disease. There is also some evidence that calcium and magnesium in drinking water may help protect against gastric, colon, rectal cancer, and pancreatic cancer, and that magnesium may help protect against esophageal and ovarian cancer. Hard water may also serve a protective role against atherosclerosis in children and teens.

Some studies have shown a relationship between the mineral content of water and eczema or dermatitis in children. However, a 2011 study from the University of Nottingham involving 336 children aged 6 months to 16 years with eczema put that relationship to the test. The researchers installed water softening units in half of the participants’ homes and monitored the children’s eczema over a period of 3 months. Using a standard scoring system, the group that received softened water showed a 20% improvement, while the group that continued with hard water showed a 22% improvement, making it unlikely that hard water is contributing to worsening eczema symptoms.

Likewise, while some studies have shown correlations between water hardness and kidney stone formation, the majority of studies have found no such relationship.

It is estimated that individuals living in hard water areas who drink 2 litres of water a day ingest about 52 mg of magnesium from their water. Considering the daily recommended intake of magnesium is 420 mg, water can account for about 12% of that.

Individuals with type 2 diabetes often experience hypomagnesemia (low magnesium) as insulin regulation requires magnesium to function. In these people, the extra intake of magnesium through drinking water could be beneficial. The heightened magnesium concentration in hard water can also benefit people experiencing chronic constipation, as magnesium salts act as laxatives. One study noted that vegetables cooked in hard water often show an increase in their calcium concentration, as opposed to the decrease seen when they’re cooked in soft water.

It is fairly difficult for humans with healthy kidneys to experience hypercalcemia (too much calcium), as any excess calcium is excreted through the kidneys. Similarly, hypermagnesemia is fairly rare, and usually just results in short episodes of diarrhea.

The Physical Effects of Hard Water

There are, however, some non-medical reasons hard water isn’t always preferable. Hard water can appear cloudy if the solubility of mineral salts is exceeded. Furthermore, if the calcium concentration surpasses 100 ppm, the water will taste “funny.” Neither of these presents a risk, but consumers prefer a “clean” appearance and taste.

Basically, while hard water can be hard on appliances and pipes, it is not hard on the body, and can actually give the daily intake of calcium and magnesium a nice little boost.

Should I Attach a Bell to My Cat’s Collar?

3 minute read
Reposted with the permission of Animal Wellness Magazine. See the original here!

Consider these pros and cons before attaching a bell to your cat’s collar.

Does your cat bring you dead animals? While this common behaviour is kind of yucky, it’s also sort of endearing – your cat is bringing you what she believes to be an excellent gift. But despite their generous intentions, hunting by domestic cats is affecting ecosystems and pushing some species to extinction. So what can you do to keep your cat from catching wildlife? There are two primary solutions to consider: keep her inside, or attach a deterrent (such as a bell) to her collar.

A closer look at the options

Of course, the easiest method of preventing your cat from killing birds and rodents is to keep her inside all the time. In the safety of your home, your feline’s exposure to prey animals will be limited to any mice that happen to get into your house. If you aren’t willing to curb your feline’s wanderlust, a common alternative is to attach a bell to her collar to alert wildlife of her approach. But is this a safe and effective option?

The pros and cons of bells

number of studies have looked at whether or not bells help prey escape from cats, and the general consensus is yes! Bells on collars seem to reduce the amount of prey caught by about half, which could be enough to no longer pose a threat to ecosystems.

Effectiveness aside, many pet parents worry that a bell will hurt their cat’s ears. According to Veterinary PhD student Rachel Malakani, a collar bell will produce sound at about 50-60 dB, but studies have shown cats to be unaffected by sounds under 80 dB. While some cats with anxiety may not react well to the bell’s sound, it’s likely that the majority of cats simply won’t care.

Some owners worry that as well as alerting prey, a bell would also alert large predators to a cat’s presence. While this is possible, given most predator’s acute hearing, it’s unlikely that the relatively quiet noise of a bell would make the difference between your cat getting detected or not. If you live in an area where your cat is at risk of being attacked by large animals you should probably be keeping your cat indoors anyway, or at least supervise their outdoor activities. You can also invest in a cat enclosure, which will allow your feline to enjoy the fresh air safely!

Bell Alternatives

If you’re unwilling to put a bell on your furry buddy, you do have another option – cat bibs. Sold under names like Birdsbesafe, these devices are brightly colored to alert potential prey to the cat’s presence before they can pounce. While your cat might look a bit silly wearing a rainbow bib, the scientific research on these products shows they reduce predation rates by roughly the same amount as bells. That said, the devices that rely on color to alert potential prey work much better on birds (who have very good color vision) than they do on small mammals (who generally have quite poor vision).

If you’re scared of attaching any collars or collar-mounted devices to your felines – you shouldn’t be. While fears that cats can become strangled or trapped by a collar caught on debris are common, actual adverse effects from collars are rare. One study looked at 107 veterinarian practices and found only one collar-related injury per every 2.3 years, with collar-related deaths being even rarer. You can mitigate your fears further by using a breakaway collar.

If your cat ventures outdoors, especially if you live in an area with endangered species, please do your part to aid conservation efforts by outfitting your kitty with an anti-hunting device.

Why Mosquitos Bite You and How to Make Them Stop

Originally posted here: https://mcgill.ca/oss/article/health-technology/why-mosquitos-bite-you-and-how-make-them-stop
15 minute read

Summertime means hammocks, BBQs, fireworks, and mosquito bites.

At least it does for me. Those rotten little suckers seem to just love me. They’ll flock to me even when there are three other people sitting in my backyard. What is it about my blood that they seem to enjoy so much?!

Let’s take a look at the science behind mosquitos and try to answer two questions: Why do mosquitos bite certain people, and what should we do to make them stop?

Take-home message:
– Blood type may or may not play a role in attracting mosquitos
– Products using DEET, icaridin, PMD, metofluthrin, and some blends of essential oils are effective at repelling mosquitos
– Bug zappers, sonic devices, citrosa plants, B vitamins, and scent-baited traps are not effective at repelling mosquitos and should be avoided

Mosquito isn’t a Species, it’s a Group

Before discussing the nitty-gritty of mosquito attraction, we need to realize something. While we tend to think of all flying bugs with proboscises as mosquitos, in truth there are more than 3500 species categorized into 112 genera that fall under the moniker of mosquito.

With such variation in species comes a lot of variation in habitats, behaviours, and risks. For instance, malaria is transmitted to humans only by mosquitos of the genus Anopheles, while yellow and dengue fever are transmitted by those in the genus Aedes. Canada is home to roughly 82 species of mosquitos belonging to the genera Anopheles, Culex, Aedes, Mansonia, and Culiseta. Some mosquitos are anthropophilic, meaning that they preferentially feed on humans, while others are zoophilic and preferentially feed on animals.

We’re typically taught to remove standing water from our property and avoid boggy or marshy areas (good luck in Ontario) to avoid mosquitos, but some species of these bugs don’t exclusively lay their eggs in water. We tend to think of mosquitos being at their worst in the summer, at dusk and dawn, but different species are active at different times, and their behaviour can even change from season to season, making it hard to predict when we are at risk of getting bitten.

Something that is true of all mosquito species though is that only the females bite. They require a blood meal in order to produce their eggs. The nasty by-product of this reproductive cycle is that they transmit diseases, and actually kill more people per year than any other animal.

How Mosquitos Track You

Mosquitos home in on their dinner-to-be by following a few different signals. The first clue that something biteable is nearby is the detection of a COplume exhaled on the breath of mammals and birds alike.

The amount of CO2, however, does not affect the attractiveness of a specific target, so even if you’re a human who produces more COthan others (such as those who are larger or pregnant) that alone is not responsible for your irresistible-to-mosquitos aura. This makes sense since large animals like cows naturally produce much more COthan humans, yet many mosquito species still prefer to bite us.

Mosquitos will track a CO­plume until they encounter host-cues. These first of these clues that a target is close by is usually smells emanating from the skin, which we’ll discuss more in a second. As they get close to the source of a smell, mosquitos will then detect and head towards heat and moisture signals emanating from a body.

Source: https://www.sciencedirect.com/science/article/pii/S096098221500740X

We don’t know whether changes in body temperature affect how attractive you are to a mosquito, but we do know that sweating increases the volatile compounds on your skin that they love, and that anhidrotic people, or those who show decreased sweating, are less attractive to the pests.

The main mosquito-cues that can differ between humans are the olfactory ones. While it’s easy to swap your shampoo and soap for unscented varieties that won’t attract mosquitos like the sweet-scented ones do, a lot of the smells that mosquitos sense are innate to your physiology and sadly are not something that we can really change.

A few of these odorous chemicals include ammonialactic acidsulcatone, and acetone. For many of these compounds, however, higher concentrations don’t equal greater mosquito attraction. Instead, they modulate the attractiveness of other substances. For instance, lactic acid has been shown to increase mosquitos attraction to ammonia and CO2.

While an animal may produce similar-to-human levels of CO2, humans tend to produce more lactic acid than primates or cows. This lactic acid synergistically increases the appeal of CO2for anthropophilic mosquito species, while actively dissuading zoophilic species from landing on you. Conversely, ruminants like cows also exhale1-octen-3-ol, a substance that attracts zoophilic species of mosquitos. In a demonstration of this, skin rubbings taken from cows were made just as attractive to anthropophilic mosquitos as skin rubbings from humans via the addition of lactic acid.

The Role of Blood Type

There has been significant debate over the role blood type plays in attracting mosquitos. Initially, a 1972 study using Anopheles gambiae found that mosquitos preferred those with O type blood (O>B>A>AB). But a 1976 study using the same mosquito species did not confirm this.

1980 study examined 736 patients and found that while those with A type blood made up 17.6% of the control group, they made up 29% of the malaria cases. Conversely, those with type O blood made up 33% of the control group but only 22% of the malaria cases. While this alone does not tell us whether or not certain blood types are more likely to be bitten by mosquitos or contract malaria, it does point to blood type playing some role in mosquito attraction.

Some clarity came with a 2009 study done with Aedes albopictus that found a similar pattern to the original 1972 study: O>B>AB>A. The researchers also compared the mosquito-attracting ability of those who secrete substances corresponding to their blood type onto their skin, versus those who do not. Their theory was that these blood type-specific secretions could explain mosquito’s ability to find their preferred type O prey. Their results, however, showed an order of preference of O secretors>A nonsecretors>B secretors>O nonsecretors>A secretors>AB secretors>B nonsecretors, which do not correspond to the blood type preferences established.

Concerning blood type’s role in attracting mosquitos, we’re stuck with the often-written phrase more research needed. Given the conflicting results and relatively small sample sizes of these studies, we cannot make definitive conclusions. Not to mention that we have no idea how mosquitos are able to detect a target’s blood type from a distance.

If mosquitos do truly target those with type O blood, the authors of this study theorize that preference could have evolved due to the prevalence of type O blood in African nations. The three most populous African nations are Nigeria, Ethiopia, and Egypt, and the percentage of their populations with type O blood are 51.3%, 39.0%, and 52.0% respectively.

How to Avoid Getting Bitten

Anyways, even if we knew what blood types attract mosquitos, you can’t change your blood type. So, what can you do to get some relief from these minuscule menaces?

First, it’s important to remember that just because you’re not forming welts doesn’t mean you’re not getting bit. Not all bites will lead to the familiar welts, so even if you’re not covered in itchy bumps, if you’re near mosquitos you should be using repellant.

Things That Work

Physical barriers should be your first line of defence against mosquito bites. Install screens on your windows, doors, tents, and RVs, and cover children’s cribs, playpens, and strollers with fine mesh to keep mosquitos out.

You can get specialty meshes and clothing treated with permethrin, an insecticide, for adults in Canada. The anti-mosquito effects of the chemical will last through several wash cycles, but permethrin-treated objects should never be used for or around children, including screens or mosquito nets that they may interact with, as their safety has not been evaluated.

In general, you should strive to wear light coloured clothing, and cover as much of your skin as the heat will allow. Mosquitos are better able to orient themselves towards darker targets, so skip the Nirvana t-shirt and try on a white tee instead.

Flowery and fruity scents will attract mosquitos greatly since they feed on flower nectar (in addition to us) but even non-botanical scented products should be avoided whenever possible. This includes (amongst many others): shampoo, soap, conditioner, shaving cream, aftershave, perfume, deodorant, hand cream, makeup, and even laundry soap and softener.

In terms of repellants, the good news is that you have more options on the market than ever. The bad news is that only some of them work.

DEET

N,N-Diethyl-meta-toluamide, better known as DEET, has been the standard ingredient in commercial bug sprays since 1957 when it made the jump from military to civilian applications. While it used to be thought that DEET interfered with a mosquito’s ability to detect lactic acid, more recent research has found that mosquitos detect and avoid DEET directly. Much like I do with vinegar.

Misguided fears about DEET’s safety have spurred some to move towards other mosquito repellants, and while there are other effectual repellants, none work as well or for as long as DEET. In terms of its safety, DEET has been more thoroughly studied than any other repellant and when used according to guidelines is quite safe.

When utilizing DEET-based repellants it’s important to pay attention to the concentration of DEET in the product. The Government of Canada recommends that no concentration over 30% be used on anyone and that only formulations containing up to 10% be used on children aged two to twelve (up to three daily applications) and aged 6 months to 2 years (only one daily application). Babies under 6 months should be kept mosquito-bite free through the use of nets and screens rather than repellants of any type.

Icaridin 

Icaridin, also known as picaridin, is a safe alternative to DEET popular in Europe and recommended by the Government of Canada for use against mosquitos and ticks on anyone over the age of 6 months. This study showed that products with 9.3% icaridin can repel mosquitos for up to 3 hours, while this study showed that a 10% concentration repelled mosquitos for more than 7 hours. This is comparable to the 5 to 7+ hours of protection provided by 7-15% DEET products, although DEET has been more widely studied. Contrarily this study found a 10% icaridin repellant rather ineffective. If you find them effective, icaridin-based products could be particularly useful for small children who have exceeded their daily recommended applications of DEET-based products but still need to remain outside.

Citronella

Citronella has long been the standard of backyard BBQs and picnics in its candle form, but in addition to the coils and candles designed to keep mosquitos out of a particular area, there are also repellants that contain citronella oil.

Citronella oil is made mostly from 2 species: C. nardusand C. winterianus, and contains many different chemicals, the most notable in terms of their insect-repelling nature include camphor, eucalyptol, eugenol, linaloolgeraniol and citronellal.

While it’s citronellal that provides the flowers with their characteristic lemony scent, a 2008 study’s findings suggest that it is actually linalool and geraniol that provide the bug-repelling effects. The researchers compared candles made of 5% citronella, linalool, and geraniol, and found the geraniol and linalool candles much more successful at repelling mosquitos than normal citronella (85% and 71% versus 29% repellency rates over 3 hours). This study likewise confirmed straight citronella candle’s inability to effectively repel mosquitos alone.

This study examined three mosquito repellants that contained citronella and found them all significantly less effective than formulas containing DEET or icaridin, and this study examined 3 wearable bracelets that claimed to emit geraniol and found them as effective as using no repellant at all.

So while it could be useful to burn a geraniol or linalool candle while you’re sitting outside, you should probably still backup your protection with an effective repellent.

P-Menthane-3,8-diol (PMD)

Products with p-Menthane-3,8-diol, a chemical found in small amounts in oil extracted from the lemon eucalyptus tree, have generally (studies 1,2,3) show it to be as effective as DEET and icaridin. The Canadian government recognizes PMD’s repellency effects on blackflies and mosquitos but recommends against using PMD-containing products on anyone younger than three.

Soybean and Essential Oils 

Soybean oil is perhaps the strangest bug-repelling ingredient on this list, but repellant formulations containing mixes of soybean oil and various essential oils have been rapidly making their way onto the Canadian market. While the soybean oil itself does not repel mosquitos, it works in tandem with the essential oils also included in the repellants to stabilize their volatility.

This study found that a formulation including soybean oil, coconut oil, geranium, and vanillin repelled mosquitos for more than 7.2 hours. However, the same study, and another, showed that other formulations also containing soybean oil, as well as other various essential oils (menthol, eucalyptus, lavender, rosemary, sage, etc.) worked very minimally.

This points to the particular essential oils and other ingredients in the repellant making the difference rather than the soybean oil itself. This makes sense when you consider that the geranium included in the effective soybean repellant was likely citronella, and that vanillin has been shown to increase the repellency effects of citronella.

The Government of Canada doesn’t place any age restrictions on formulas containing soybean oil but recommends not using essential oil formulations on those younger than 2. So, you’re free to experiment with different products using different ingredient blends and see which works, but make sure to turn to something a bit more reliable when actually venturing into the woods.

Metofluthrin 

If you’d rather wear a clip-on device than use a mosquito repelling lotion or spray, your only good option is those that emit metofluthrin. This 2017 study examined the efficacy of 5 wearable anti-mosquito devices and found that only the metofluthrin at a concentration of 31.2% effectively repelled mosquitos. Much like citronella candles, however, clip-on devices work by creating a fog of mosquito-repelling chemicals around you. This means that they will only be effective for times when you’re sitting still.

Things That Don’t Work

While components of citronella oils may be effective repellants, citrosa houseplants are not. Nor are the sonic mosquito repelling products that claim to play sound at frequencies that will drive mosquitos away. I’ll let the authors of this paper sum up the evidence for these products: “We are not aware of any scientific study showing that mosquitoes can be repelled by sound waves and therefore we consider these devices as the modern equivalent of snake oil”.

While synthetic mosquito lures that attract the bugs just as well, if not better, than humans have been developed, in practice mosquitos continue to be attracted to humans even when these devices are used. Thus, their use is not recommended by the Canadian Government. Likewise, handheld or mounted bug zappers certainly exist and can be quite satisfying to use for revenge on the bugs that stole your blood, relying on them for protection is not a good idea.

You may have heard that eating bananas can alternatively make mosquitos more or less attracted to you. The claims of banana’s repelling power stem from their high vitamin B6 content, but a 2005 study tested the effects of vitamin B consumption on mosquito attraction and found absolutely no effects. In terms of bananas attracting power, those claims come from octenol content, a chemical that does indeed attract mosquitos. But, octenol isn’t unique to bananas, it’s found in many foods, and no studies have been done that prove consuming bananas does make you a bug-target, so keep on munching.

A subtler mistake you may make when selecting your mosquito repellant is to use a product that combines sunscreen and bug spray. While certainly convenient, the problem lies in sunscreen’s need to be reapplied much more frequently than mosquito-repellants. If both products are needed for an outing, it’s recommended that you wait 20 minutes between applying sunblock and repellant.

Basically, to avoid being a mosquito-target you should stay as scent-free as possible, wear light clothes, avoid bogs and use an effective repellent (such as those containing DEET or icaridin). Or, you could always stay inside- I hear its quite nice this time of year.