What percent of deet (in bug spray) is safe for a toddler? 7% does not work and he keeps getting bites!

Works used right. The trick for deet products is realizing that the active ingredient evaporates. You get about an hour for every 10%, so the low end products must be re-applied frequently.30% is okay but will still be lost after about 3hrs.
Up to 25% Deet-containing insect sprays have been proven safe in children over the age of 2 months. Use the minimum amount necessary and avoid the eyes, nose and mouth when applying. Non-deet sprays are available but often aren't as effective.