Pretest your perm. Common causes of dermatitis at the hairline are chemicals in permanent solutions and hair dyes. Again, you can head off this type of allergic dermatitis by patch-testing yourself with the solution or by asking your hair stylist to do so. If you're doing the test yourself, home kits usually have instructions on the box. Be a good sport.
Some exercise equipment contains materials that trigger allergic contact dermatitis.
Things that can be troublesome include the rubber additives in tennis shoes, masks and mouthpieces, swim caps, swim goggles, diving suits, nose clips, earplugs and swim fins. Athletic tape can also be a problem for people allergic to formaldehyde resins. So if you have a rash in an area that one of these products touches, consider finding an alternative. Look out for latex. You may want to try gloves or condoms that are not made of latex.