I was recently asked, by a favorite target of mosquitoes, about using oral or pill form mosquito repellents. Great question! You can see the question posted here.
A very well written and informative article titled Mosquitoes and Mosquito Repellents: A Clinician’s Guide is a fantastic resource for most information about “all things mosquito repellent”. The short answer to the question of oral mosquito repellents is, simply, no.
DEET(N, N-diethyl-meta-tolumide) is the most studied, effective and advised method of preventing mosquito bites. An oral or transdermal (skin patch) method of mosquito bite prevention has been the “holy grail” of vector borne disease prevention for many years. To date, there is not an effective product.
There have been attempts to show that garlic, bananas and vitamin B can be taken orally and prevent mosquitoes. This is not true. There are numerous and respected studies that have looked at these methods and all have shown that there is no protection from Garlic, Vitamin B or any other ingested methods of bite prevention. The university of Wisconsin conducted a good study that showed vitamin B was ineffective. Several good sites can be found here:
Mosquito Repellents (general)
There are a few things that are proven to work, in decreasing mosquito bites:
Use DEET as directed and do not exceed 30-35% concentration for adults and 10% for children
Avoid being outside during traditional peak mosquito hours (dusk and dawn)
Long sleeves and pants, with a mesh hat/veil if needed!
Permethrin impregnated clothing and bed nets
An original post on this subject can be found here: