DEET is the gold standard insect repellent, effective against mosquitoes, ticks, chiggers, and biting flies. Developed by the US Army in 1946 and registered for public use in 1957. Higher concentrations last longer but don't repel better — 30% DEET provides up to 8 hours of protection.
Mosquitoes (all species), ticks (deer tick, dog tick, lone star), chiggers, biting flies, gnats, fleas (limited), sand flies, no-see-ums. NOT effective against: stinging insects (wasps, bees), spiders, bed bugs.
OFF! Deep Woods (25% DEET), Repel 100 (98.11% DEET), Sawyer Premium (30% DEET), Cutter Backwoods (25% DEET), Ben's 30 (30% DEET), Ultrathon (34.34% DEET, extended release). Many store brands available.
Safe when used as directed. Apply to exposed skin and clothing — not under clothing. Avoid eyes, mouth, and broken skin. Do not apply to children's hands (they touch their face). 10-30% concentration is sufficient for most situations. Wash off when returning indoors.
Can damage some plastics, synthetic fabrics, and watch crystals. Will not damage cotton, wool, or nylon.
Concentration guide: 10% = ~2 hours, 24% = ~5 hours, 30% = ~8 hours. Higher than 30% does NOT repel better — only lasts marginally longer. For most backyard situations, 20-30% is ideal.
Application tip: Light, even coating is more effective than soaking. Reapply after swimming or heavy sweating. Can be combined with sunscreen (apply sunscreen first, then DEET).
Tick protection: For tick-endemic areas, combine DEET on skin with permethrin-treated clothing for maximum protection. This combination is the CDC-recommended approach for Lyme disease prevention.