I was listening to the radio on my way to work today and heard of a skin condition called mobile phone dermatitis, which essentially is a skin rash on the ears, face, or fingers. The condition is mostly found on people who has skin exposure to metal elements of the phone, usually the casing. The condition is caused by exposure to nickel in the metal. The condition could also be caused by excessive phone use.

According to MobileBurn:

Lionel Bercovitch, of Brown University in Rhode Island, tested 22 of the most popular cell phone models in the United States earlier this year and found nickel to be present in nearly half of them. Nickel has previously been found to cause skin irritations, and is likely the culprit here, too.