Will Vitamin B1 Scare Mosquitoes Away?

Mosquitoes can put a real damper on enjoying the outdoors. When we were on our honeymoon, many years ago, we were camping in Grand Teton National Park. Even before we opened the car doors to set up our tent and camp stove, there were enormous mosquitoes hovering in large numbers to get a bite of our blood. Quite intimidating!

Why Are Some People Especially Enticing to Mosquitoes?

There seem to be significant differences among individuals with respect to how attractive mosquitoes find them. Some people start slapping biting mosquitoes the second they step outside, while others are rarely troubled at all.

An article at Smithsonian.com suggests several factors that may help explain this curious phenomenon. It turns out that blood type matters, and so does body temperature and the amount of carbon dioxide a person exhales. The microbial ecology of the skin may also have an effect on mosquitoes and their likelihood of taking a taste. Be wary at the backyard cookout: people drinking beer appear to be especially appealing to mosquitoes.

Taking Vitamin B1 to Discourage Mosquito Bites:

Q. I seem to remember you once mentioned vitamin B1 to repel mosquitoes. I have been taking it ever since.

Apparently, the vitamin makes your skin smell and repel mosquitos. People don’t notice the odor.

I felt a daily dose of B1 would not be harmful to me. Lately I have noticed that others are itching and waving their hands to ward bugs off while I am fine. Even when bugs are flying around, they don’t land on me.

A. We certainly appreciate your testimonial. Other readers have also reported surprising success with this approach.

Unfortunately, there have been few studies of this approach. Entomologists generally dismiss this oral vitamin as ineffective (Bulletin of Entomological Research, Aug. 2022). Unfortunately, some of the diseases mosquitoes carry, such as Zika or West Nile virus are very serious. As a result, you might think twice about using vitamin B1 when such pathogens are present. You wouldn’t want to risk catching them by using an unproven repellent.

Does Vitamin B1 Scare Mosquitoes Away?

Many other readers are enthusiastic about vitamin B1 against mosquitoes.

Q. I am a gardener and have always been a mosquito magnet. After reading about vitamin B1 several days ago, I started taking it. I just went outside this evening and didn’t get one bite! Usually they are all over me. I will continue to take B1 until cold weather.

A. There is almost no scientific research to support vitamin B1 (thiamine) against mosquitoes. That said, some readers report similar success. It may well be that thiamine works in conjunction with some of the other individual factors to make certain individuals less appealing.

We heard before from an individual who had good luck like you do:

Q. I have found vitamin B1 to be an effective deterrent for mosquito bites. Recently, I was in an area where I got multiple mosquito bites daily that itched unbearably. I developed open sores from scratching in my sleep, even when I used Benadryl or hydrocortisone cream.

In less than a week of taking vitamin B1 (500 mg per day), I have not had any more bites. Perhaps there are studies that say vitamin B1 has no value for deterring insect bites, but my experience convinces me otherwise.

A. Thank you for sharing your testimonial. Some other readers have also found taking vitamin B1 (thiamine) helpful against mosquitoes. The research we found, however, indicates that this vitamin is not effective as a systemic mosquito repellent (Journal of the American Mosquito Control Association, June, 2005). We could find no more recent research on the effects of thiamine against mosquito bites.

Another reader used B vitamins as a repellent in quite a different way:

Q. High in the Canadian Rockies where I was hiking, the black flies were voracious. I didn’t have insect repellent with me because mosquitoes, fleas and other critters never bite me. Maybe that’s because I take B-complex and garlic, among other supplements, and they don’t like that.

Increasingly vexed by the black flies, I finally appropriated a B-complex 100 mg tablet I had with me. I smushed it up with some creek water, and then rubbed the bright yellow liquid all over myself. END OF PROBLEM! I admit, though, that I did look a bit jaundiced. What do you think about the efficacy of B-complex or other supplements in repelling bugs?

A. We love your story, but we’ve never heard of anyone else using vitamin B pills topically. With no studies, we wouldn’t dare venture a guess about effectiveness.

There was some preliminary research on thiamine, a B vitamin, taken orally to repel mosquitoes. Since it was conducted many decades ago, however, it would not meet today’s scientific standards and newer research has not confirmed the benefit. Nevertheless, some readers swear that this nutrient keeps mosquitoes from biting them.

Repelling Mosquitoes:

Individual body chemistry seems to have an important effect on whether and how well this remedy works. Most people need to apply a proven mosquito repellent such as DEET, picaridin or lemon eucalyptus oil. That is particularly true in places where mosquitoes may be transmitting malaria, Zika virus or West Nile virus. Although DEET sets the standard for repellents and has for decades, there are concerns about toxicity, especially if it is being used for extended periods or at high concentrations.

We have written here about mosquito repellents. It turns out that different species are more sensitive to one repellent than another (Travel Medicine and Infectious Diseases, Nov-Dec., 2013). That might explain why some people find taking thiamine helps, at least under certain conditions. Adding vanillin to mosquito repellents can extend the amount of time they are effective by about two hours.