A new study suggests there could be a link between skin allergies and the risk of developing certain cancers.
In research released on Monday, Danish researchers followed nearly 17,000 Dutch adults who were tested for skin allergens over a 23-year period. More than 6,000 of them tested positive for an allergy to at least one chemical or metal, and those people were found to be at a lower risk of non-melanoma skin cancers and breast cancers, but at a higher risk for bladder cancer.
But these results don't mean that people with skin allergies are at a higher or lower risk for cancer. The authors stress the study merely suggests an association between skin allergies and cancer risk, although they believe it does offer more proof of the immunosurveillance hypothesis.
"Theoretically, the authors believe skin allergies put the immune system in overdrive, which is called the immunosurveillance hypothesis" said Dr. Clifford Bassett, assistant clinical professor of medicine at NYU Langone School of Medicine. Bassett was not involved in this research. "This means the immune system may be super-responsive, and perhaps there's some protective function and therefore, the immune system is prehaps more likley to fight off certain things, including cancers."
The researchers believe that the increased risk of bladder cancer could have been due to a number of factors, including the buildup of chemicals in the urine, the use of hair dye and smoking.
Other experts say this is one of numerous studies that assessed the relationship between allergies and cancer and so far, results have been inconclusive. Nonetheless, they believe this study's findings may add to our understanding about how the immune system functions.
"It's an interesting theory," said Dr. Stanley Fineman, president-elect of the American College of Allergy, Asthma and Immunology. "There's a lot we're learning about the immune system."
Other types of allergies, such as allergies to pollen, ragweed and other inhaled substances, don't affect the immune system the same way as skin allergies do. Skin allergies are known as type 4 allergies and hay fever is know as a type 1 allergy.
"There are different immunological mechanisms involved," said Fineman. "Type 4 involves the T cells, and with type 1, there's some involvement with T cells, but they are not immediately involved. Certain types of T cells are involved in destroying tumors.
"Some people will never develop an allergy if they're exposed to something and their T cells don't develop a sensitivity," said Dr. Sandra Hong, a staff physician at The Cleveland Clinic.
Skin allergies are also known as allergic contact dermatitis. According to the Asthma and Allergy Foundation of America, the most common allergens in adults are poison ivy, poison oak and poison sumac.
Other common allergens are metals such as nickel and substances found in cosmetics and fragrances. Experts believe the reason skin allergies are about twice as common in women is because of nickel found in jewelry as well as cosmetics and perfurmes, which are more often used by women.
"About 25 chemicals appear to be responsible for skin allergies," said Bassett. Doctors diagnose skin allergies through a method called patch testing.
"There are chemicals on the patches, and they're applied to the back and read multiple times, but days later," said Hong. The presence of a rash helps doctors determine whether an allergy exists.
The easiest treatment is to avoid contact with the allergen, but for more severe cases, doctors may prescribe steroids.
And allergists may find themselves doing a lot more treatment prescribing for all kinds of allergies.
"The prevalence of allergic diseases is on the rise, but we don't really know why."