An old medical myth suggests that taking vitamin B1, also known as thiamine, can make your body repel mosquitoes.
A "systemic repellent" that makes your entire body unattractive to biting insects sure sounds good. Even if you rightly reject the misinformation that questions the safety and effectiveness of repellents like DETA, oral repellents still have the advantage of not having to worry about covering every inch of exposed skin or carrying around cans of insecticide. every time you go out. .
In addition to thiamine, other purported oral mosquito repellents include brewer's yeast, which contains thiamine, and garlic, a legendary vampire repellent.
If oral repellents seem too good to be true, that's because they are.
As a professor of entomology in Taiwan, where the mosquito-borne dengue virus is endemic, I was interested to know what the science really says about food repellents. After a very deep dive into the literature and almost every article ever written on the subject, I compiled this knowledge into the first systematic review on the subject.
The scientific consensus is unequivocal that oral repellants do not exist. Despite extensive research, no food, supplement, drug or condition has ever been proven to make people sick. People deficient in vitamin B1 also no longer attract mosquitoes.
So where does the myth that mosquitoes hate vitamins come from, and why is it so hard to dispel?
Also read | Why are some people attracted to mosquitoes and others indifferent?
Create a myth
In 1943, Minnesota pediatrician V. Ray Shannon gave 10 patients different doses of thiamine, which had been synthesized just seven years earlier. They reported that it reduced itching and prevented further mosquito bites. In 1945, California pediatrician Howard Eder announced that doses of 10 milligrams could protect people from fleas. In Europe in the 1950s, Dr. Dieter Müting claimed that daily doses of 200 milligrams protected him from bites while on vacation in Finland, and suggested that the breakdown products of thiamine are excreted through the skin.
These discoveries quickly attracted attention and were dismissed almost immediately. The US Naval Medical Research Institute attempted to replicate Shannon's findings but failed. In 1949, Californians who used thiamine to repel fleas on dogs declared it "totally useless." Controlled studies from Switzerland to Liberia have repeatedly found no effect at any dose. The first clinical trial, conducted in 1969, definitively concluded that "vitamin B1 is not a human systemic mosquito repellent," and since then all controlled studies have suggested the same for thiamine, brewer's yeast, garlic, and others.
The evidence was so compelling that in 1985 the US Food and Drug Administration declared that all oral insect repellents "are not generally recognized as safe and effective and are mislabeled," making the supplements technically infallible. .
There are no medical mechanisms.
Today, scientists know much more about mosquitoes and vitamins than ever before.
Vitamin B1 does not break down in the body and does not affect the skin. The body tightly regulates this, absorbing only a small amount of thiamine after the first 5 milligrams and quickly excreting the excess in the urine, so it doesn't build up. An overdose is almost impossible.
As in humans, thiamine is an essential nutrient for mosquitoes. They have no reason to fear it or try to avoid it. There is no evidence that they can smell it.
The best sources of thiamine are whole grains, beans, pork, poultry and eggs. If a carnitas burrito doesn't keep mosquitoes away, neither will a pill.
Also read | Decode the smell of mosquitoes
So what explains the early reports? In addition to poor experimental design, many have used individual patient reports of fewer bite symptoms as an indicator of reduced biting, which is not a good way to get an accurate picture of what happened.
After a mosquito bite, there are two reactions: an immediate reaction, which starts quickly and lasts for hours, and a delayed reaction, which lasts for several days. The presence and intensity of these reactions does not depend on the mosquito, but rather on your own immune system's familiarity with that species' saliva. With age and prolonged exposure, the body goes from no reaction to only a delayed reaction, both to only an immediate reaction, and finally to no reaction at all.
What Shannon and others thought was disgust may have been desensitization; patients were still bitten, they just stopped showing symptoms.
So what is the problem?
Despite the scientific consensus, a 2020 survey of pharmacists in Australia found that 27% still recommend thiamine as a repellent for patients traveling overseas; unacceptable proposal. Besides wasting money, people who rely on vitamins to repel mosquitoes can still get bitten, potentially exposing them to diseases like West Nile and malaria.
To circumvent the US ban and the accepted scientific consensus on oral repellents, some unscrupulous dealers manufacture thiamine capsules or even injections. Unfortunately, although thiamine is safe to take by mouth, it can cause severe allergic reactions when taken by other routes. Therefore, these products are not only useless, but also potentially dangerous.
Not all problems can be solved with food. Long-sleeved clothing and products containing DETA, picaridin or other proven repellents are still your best protection against insect bites.
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