Why would I get dermatitus, I have never had it before?

Anon - Dermatitis is a general term that's used to describe an inflammation of the skin. Have you ever had allergies or been tested for allergies? Some of the things you're describing, such as having a reaction to earrings, could indicate an allergic reaction.

It's possible to develop adult onset allergies to things that were not bothersome at earlier ages. For example, I've had a pet cat my entire life, but developed an allergy to cat dander as an adult. This came as quite a surprise!

Dermatologists sometimes use patch testing to determine what is causing the inflammation leading to dermatitis. In this test, your doctor applies small amounts of various substances to your skin under an adhesive covering. During return visits over the next several days, your doctor examines your skin to see if you've had a reaction to any of the substances. This type of testing is most useful for determining if you have specific contact allergies.

Allergists also conduct testing, which is more extensive and also more exact. This link provides information on allergic reactions related to the skin, including those to hair dyes and metals.
http://www.medicinenet.com/allergy/page7.htm#skin

Hope this helps! Pat