Vitamin B1 (Thiamine) acts as a coenzyme necessary for the conversion of carbohydrates into glucose, which is burned in the body for energy. It is essential for the functioning of the nervous system, and a deficiency can cause beriberi, a disease marked by weakness, paralysis and oedema. Some recent studies have suggested that taking large doses of thiamine ( Vitamin B1 ) is effective in reducing mosquito bites. This safe vitamin apparently produces a skin odor that is not detectable by humans, but is disagreeable to pregnant mosquitoes.