DEET really is a toxic substance, and if it weren't that our tolerance for mosquitoes is so low, we probably would have banned its use long ago. DEET was developed by the US military in 1946, if that is any indication of the low level of safety concern in the chemical's development. There are certainly more toxic insect repellents out there, and DEET is much less detrimental to birds and other forms of life than many insect-targeting chemicals, but it still is a chemical that can burn through plastics and synthetics. DEET products strongly discourage its use around the eyes and mouth or simple cuts and scrapes, and users are encouraged to wash the product off as soon as it is no longer needed. Ingestion can be fatal and use on children is discouraged. Fortunately, natural alternatives can be just as effective, and the primary advantage in DEET is simply that it is longer lasting. Multiple applications of natural repellents can overcome this advantage entirely.