NEW YORK -- Smoking may increase the risk of developing allergies to a wide variety of materials, including metal found in earrings and in the buttons of blue jeans, a group of Danish researchers has found.

In the study of more than 1,000 men and women ages 15 to 69, such allergies were more common in people who smoked or used to smoke, according to a report in the May issue of the Journal of Allergy and Clinical Immunology.

So-called contact allergies are reactions -- such as red itchy skin -- that occur in response to touching a particular substance.

Dr. Allan Linneberg at Glostrup University Hospital in Copenhagen found that contact allergies to nickel -- which is found in earrings and in the buttons to blue jeans -- were more common among smokers. Although allergies to nickel sometimes develop in people who wear earrings, smokers had an increased risk of nickel allergy whether or not they wore earrings.

"I think it is safe to say that this study points out yet one more reason for people not to start smoking, and if they smoke, to quit," said Dr. Kathleen A. Sheerin of the Atlanta Allergy and Asthma Clinic in Georgia, who was not involved with the study.

Sheerin told Reuters Health that as this appears to be the first study of its kind to explore the relationship between smoking and contact allergy, more research will be needed to understand the reason for the connection.

The researchers note that they do not yet know exactly how smoking might lead to the apparent elevated allergy risk.

If future research supports the link between smoking and an increased allergy risk, smokers might find that kicking the habit may prevent some cases of allergies, according to the report.