Myth debunked: Mosquitoes aren’t repelled by vitamin B1 or dietary supplements

A long-standing medical myth says that taking vitamin B1, also known as thiamine, helps your body repel mosquitoes.

A “whole body repellent” that dislikes insect bites all over the body certainly looks good. Even if you rightly reject the misinformation that calls into question safe and effective repellents like DEET, oral repellents include covering every inch of exposed skin and using insect repellent every time you go outdoors. The advantage is that you don’t have to worry about carrying around a can of spray. .

In addition to thiamine, other questionable oral mosquito repellents include brewer’s yeast, which contains thiamine, and garlic, the legendary vampire repellent. Because it’s a street.

As a professor of entomology in Taiwan, where mosquito-borne dengue is prevalent, I was curious what the science really said about food-based repellents. After reading nearly all the papers published, I have combined this knowledge into the first systematic review on the subject.

The scientific consensus is, unequivocally, that there are no oral repellents. Despite extensive searches, no food, supplement, drug, or condition has been proven to repel people. People with vitamin B1 deficiency also do not attract mosquitoes.

So where did the myth that mosquitoes hate vitamins come from, and why are they so difficult to get rid of?

myth making

In 1943, Minnesota pediatrician W. Ray Shannon administered thiamine, which had first been synthesized seven years earlier, to ten patients. They reported that it soothed itching and prevented further mosquito bites. In Europe in the 1950s, physician Dieter Muting claimed that taking a daily dose of 200 milligrams while vacationing in Finland eliminated chewing and reduced the breakdown of thiamine. I hypothesized that the substance was excreted through the skin.

These findings quickly gained attention and were almost immediately disavowed. The United States Naval Medical Laboratory attempted to replicate Shannon’s findings, but was unsuccessful. By 1949, Californians using thiamine to ward off fleas from their dogs reported that thiamine was “totally worthless”. The first clinical trial in 1969 conclusively concluded that “vitamin B1 is not a systemic mosquito repellent in humans”, and all subsequent controlled studies have found that thiamine, It suggests the same for brewer’s yeast, garlic, and other substitutes.

In 1985, the U.S. Food and Drug Administration declared that all oral repellents were “not generally recognized as safe, effective, and misbranded,” and prohibited supplements from being labeled as repellents. was technically a fraud, and the evidence was quite overwhelming.

no medical mechanism

Scientists today know more about both mosquitoes and vitamins than ever before.

Vitamin B1 is not broken down in the body and has no known effects on the skin. The body regulates it so strongly that it absorbs very little thiamine after the first 5 milligrams, and the excess thiamine is quickly excreted via urine and therefore does not accumulate. Overdose is almost impossible.

As in humans, thiamine is an essential nutrient for mosquitoes. There is no reason for them to fear or avoid it. There is also no evidence that they can smell it.

The best sources of thiamine are whole grains, beans, pork, chicken and eggs. If eating a carnitas burrito doesn’t keep mosquitoes away, you should also avoid the pills.

So what explains the early reports? In addition to poor experimental design, many used anecdotal patient reports of less bite symptoms as a proxy for bite reduction. , which is not a good way to figure out exactly what’s going on.

Two reactions follow after a mosquito bite. There are immediate reactions that begin immediately and last for hours, and delayed reactions that last for days. The presence and intensity of these responses depends on the proficiency of your own immune system to the saliva of that particular species, not the mosquitoes. Both, immediate reaction only, and eventually change to no reaction.

What Shannon and others considered repellent may have been desensitization. The patient was still bitten, but he just stopped showing symptoms.

So what’s the problem?

Despite scientific consensus, a 2020 survey of Australian pharmacists found that 27% still recommend thiamine as a repellent to patients traveling abroad. This is an unacceptable recommendation. Besides wasting money, people who rely on vitamins for protection against mosquitoes can still get stung, putting them at risk for diseases such as West Nile and malaria. there is.

To circumvent the US ban and widely agreed scientific consensus on oral repellents, some unscrupulous dealers are making thiamine patches or even injections. Unfortunately, thiamine is safe to swallow. However, other routes of intake can cause severe allergic reactions. Therefore, these products are not only worthless, but potentially dangerous.

Not all problems can be solved with food. Long sleeves and bug spray containing DEET, picaridin, or other proven repellents are your best defense against biting pests.

This article is republished from The Conversation under a Creative Commons license. Please read the original article.