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Will Vitamin B1 Keep Mosquitoes from Biting You?

Studies have not shown that taking vitamin B1 pills keep mosquitoes from biting, but new research suggests that a topical form is effective.
Will Vitamin B1 Keep Mosquitoes from Biting You?
Public domain from https://phil.cdc.gov/Phil/details.asp image id#8923 credit James Gathany

Mosquitoes are persistent insects. They are everywhere, from Maine to Alaska. In fact, Alaska Tour & Travel states: “Half-jokingly known as the Alaska state bird, mosquitos are a fact of summertime life in Alaska.” The good news in Alaska is that the peak season for mosquitoes is shorter than in many other states. For most people, mosquitoes can bite from mid-April until late-October. With climate change, though, mosquitoes could linger through November. Is there any way to keep mosquitoes from biting? That is a question many readers keep asking.

Why You Should Keep Mosquitoes from Biting!

If the mosquitoes in your area carry serious diseases like dengue, Zika or chikungunya, you should probably invest in effective commercial repellents with DEET or picaridin and use them conscientiously. If, on the other hand, the main problem is the itchy bite itself, you might be tempted to consider another approach. We have heard from quite a few readers that vitamin B1 (thiamine) may help keep mosquitoes from biting.

Can Thiamine Keep Mosquitoes from Biting?

Q. Mosquitoes love me. I used to go to a lake in Ontario for a couple weeks each summer. The fishing was awesome, but the mosquitoes were big and plentiful and would bite me, leaving lots of raised welts that itched like crazy.

Then my aunt (an OR RN) told all of us to start taking vitamin B1 (100 mg once a day) for two weeks before we leave for Canada. It worked like a charm. Mosquitoes would descend upon our boat and land on my bare skin and then take off without biting! I was able to enjoy fishing without being bitten once. I swear by the vitamin B1.

Topical Vitamin B1 vs. Oral Pills:

A. Vitamin B1 (thiamine) has been controversial as a mosquito repellent. Many people, like you, report benefit from oral doses. However, a study found it did not keep mosquitoes from biting (Journal of the American Mosquito Control Association, June 2005). Scientists have rarely studied whether taking vitamin B1 orally is effective as a mosquito repellent. One trial we found dates back many years and reached similarly discouraging conclusions (Transactions of the St. John’s Hospital Dermatological Society, 1969)

On the other hand, a tiny pilot study demonstrated that thiamine hydrochloride (vitamin B1) works as a topical mosquito repellent (Biological and Pharmaceutical Bulletin, Feb. 2020).

The researchers conclude:

“This finding can be supported by future works in which a proper formulation of thiamine hydrochloride in the respective doses would be presented. One can get prolonged safe protection against insect bites.”

Another Fan of Thiamine to Keep Mosquitoes from Biting:

This reader says that oral thiamine worked for him:

Q. You’ve published some anecdotes about vitamin B1 to repel mosquitos, and I’ll add my story to your collection. The mosquitos have been eating people alive this year far worse than usual, swarming, feeding in sunlight, like nothing I’ve ever seen before. I’ve been bitten mercilessly, as has my family.

I started taking thiamine as an experiment; the rest of my family has not. They’re still being bitten bloody and I haven’t had more than three bites since two days after the first dose.

A. Thanks for your testimonial. For decades, anecdotes were all we had on this topic. Now, however, Egyptian scientists have come up with a topical formulation of vitamin B1 that is effective as a mosquito repellent (Journal of Pharmaceutical Sciences, Aug. 3, 2021). In this study, nanospheres of thiamine were applied to skin. Surprisingly, this hydrogel was as effective as DEET.

This doesn’t answer the question whether oral thiamine is an effective repellent, but it does suggest that there is something in this vitamin that mosquitos don’t like.

Why Not Use DEET?

The compound known as DEET, aka N,N-diethyl-m-toluamide, and now called N,N-diethyl-3-methylbenzamide, is the gold standard for mosquito repellents (New England Journal of Medicine, July 4, 2002). That is why we suggest using it when mosquito bites might transmit a potentially lethal disease. 

On the other hand, readers have reported that DEET can kill grass and dissolve super glue. Many people are concerned that it poses dangers to children.

Although DEET can keep mosquitoes from biting, so can picaridin and oil of lemon eucalyptus (Wilderness Environmental Medicine, March 2016). In fact, these topical repellents are better than DEET at protecting people from ticks, blackflies, midges and sandflies. Perhaps someday soon, topical thiamine hydrochloride will join the list of effective alternatives to DEET.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
  • Ives AR et al, "Testing vitamin B as a home remedy against mosquitoes." Journal of the American Mosquito Control Association, June 2005. DOI: 10.2987/8756-971X(2005)21[213:TVBAAH]2.0.CO;2
  • Khan AA et al, "Vitamin B1 is not a systemic mosquito repellent in man." Transactions of the St. John's Hospital Dermatological Society, 1969.
  • Badawi A et al, "A pilot clinical study on thiamine hydrochloride as a new mosquito repellent: Determination of the minimum effective dose on human skin." Biological and Pharmaceutical Bulletin, Feb. 2020. https://doi.org/10.1248/bpb.b19-00538
  • Fradin MS & Day JF, "Comparative efficacy of insect repellents against mosquito bites." New England Journal of Medicine, July 4, 2002. DOI: 10.1056/NEJMoa011699
  • Diaz JH, "Chemical and plant-based insect repellents: Efficacy, safety, and toxicity." Wilderness Environmental Medicine, March 2016. DOI: 10.1016/j.wem.2015.11.007
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