LONDON (Reuters) - Doctors baffled by an unexplained rash on people's ears or cheeks should be on alert for a skin allergy caused by too much mobile phone use, the British Association of Dermatologists said on Thursday.

Citing published studies, the group said a red or itchy rash, known as "mobile phone dermatitis," affects people who develop an allergic reaction to the nickel surface on mobile phones after spending long periods of time on the devices.

"It is worth doctors bearing this condition in mind if they see a patient with a rash on the cheek or ear that cannot otherwise be explained," it said.

The British group said many doctors were unaware mobile phones could cause the condition.

Safety concerns over mobile phones has grown as more people rely on them for everyday communication, although the evidence to date has given the technology a clean bill of health when it comes to serious conditions like brain cancer.

"In mobile phone dermatitis, the rash would typically occur on the cheek or ear, depending on where the metal part of the phone comes into contact with the skin," the group said in a statement.

"In theory it could even occur on the fingers if you spend a lot of time texting on metal menu buttons."

Nickel is a metal found in products, ranging from mobile phones to jewelry to belt buckles and is one of the most common causes of allergic contact dermatitis, according to the Mayo Clinic in the United States.

Earlier this year Lionel Bercovitch of Brown University in Providence, Rhode Island and colleagues tested 22 popular handsets from eight different manufacturers and found nickel in 10 of the devices.