INSECT REPELLENTS have been the most important first line of defense against mosquito and tick bites for many years.
SKIN REPELLENTS are usually effective for one to several hours. Their effectiveness varies with each person. Some people attract more insects than others, and the effectiveness of the repellents can diminish through absorption, evaporation, rain, sweating, swimming, and wiping. They must be re-applied to remain effective. The best insect repellent know is commonly called DEET (N, N-diethyl-m-toluamide). It repels a variety of mosquitoes, chiggers, ticks, fleas, and biting flies. Some common insect repellents are: OFF, Ultrathon, HourGuard, Repel, Skedaddle! (10% DEET); and Skintastic (7.5% DEET).
OTHER REPELLENTS which can be used against mosquitoes and ticks are Rutgers 612, and dimethyl phtlalate, but they are much less effective than DEET. Citronella-based Natrapel, a natural product, may provide short-term protection against mosquitoes, but is probably not effective against ticks.
BEES AND WASPS: No topical repellent is effective against stinging insects such as bees and wasps.
CLOTHING REPELLENT: Permethrin is a repellent which is actually a pesticide. It kills insects which come in contact with it. It adheres tightly to fabric and will last through multiple washings and is non-staining and nearly odorless. It is effective against mosquitoes, ticks, flies, and other insects. It is resistant to light, heat, and immersion in water, and is biodegradable. Permethrin is not hazardous to humans. Skin absorption is extremely low. Using Permethrin is easy: clothing can be sprayed (Duranon, Permanone aerosol spray, Permanone Tick Repellent) until slightly damp, then hung to dry. It lasts about six weeks, even after several launderings. Clothing soaked in Permethrin solution (Permakill 4-week Tick Killer) will afford even longer protection.
SIDE EFFECTS OF DEET are not common. It is absorbed through the skin. Some new formulations with an added polymer apparently decrease this absorption quite significantly, thereby making it last longer (Ultrathon, HourGuard) also. It can cause itching, swelling, stinging, and blistering. Toxic reactions may occur in children, including neurological side effects such as seizures. These are very rare events. To minimize the possibility of reactions to DEET, use low concentrations on children, and wear clothing which reduces skin surfaces requiring the repellent. Permethrin is toxic to insects, but not to humans, and adverse systemic effects have not been reported in the medical literature.
From Rose/Medical Letter/Bank Berry