If you ride a bike and you want to be safer you can buy and wear a helmet...and even if you don't wear one yourself you do buy one for your child - right?
DEET is great. I needed DEET in my bag, I needed to spray it all over my head! It's great to keep bugs away. It's also very good at destroying stuff, especially bike helmets. DEET on things other than skin is typically not a great mix. It has a propensity to eat plastics, chews polystyrene (EPS) into a sticky goo, and weaken, pockmark, and discolor a lot of other man-made fabrics.