Harmful Chemicals in Mosquito Repellent.
1. DEET is one of the most widely used chemicals as a mosquito repellent. While the use of DEET in lower concentrations is considered safe, when used in concentrations greater than 50 percent, DEET can produce skin irritation. Eye irritation is also common. DEET also will penetrate skin and can, in some instances, affect the central nervous system. In some individuals, slurred speech, confusion and seizures have occurred. These symptoms are most commonly associated with long-term, excessive exposure or improper use.
2. Permethrin is another repellent intended for treating clothing and other items, such as tents, sleeping bags and other gear made of fabric. Permethrin can cause eye irritation. While pyrethroid chemicals directly affect the nervous system of insects, it is not certain how these chemicals will affect humans, so care should be taken to follow the directions carefully. The Environmental Protection Agency has also classified permethrin as "likely to be carcinogenic to humans" if ingested.
3. P-menthane-3,8-diol may have some associated health hazards. The Environmental Protection Agency has found that long-term skin exposure produces microscopic kidney lesions as well as skin redness and swelling. Canada's Pest Management Regulatory Agency states that one study found p-menthane-3,8-diol may cause genetic damage.
4. While the California Department of Pesticide Regulation Report 2007-6 indicates that there was a possible increase in liver tumors and liver necrosis in rat and mice toxicity studies, the Environmental Protection Agency has cleared Metofluthrin as safe, when properly used.