Harmful Chemicals in Mosquito Repellent | eHow
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 rare instances, affect the central nervous system.