An allergic contact dermatitis rash can occur from exposure to certain substances such as nickel, poison ivy, creams or cosmetics. The result is a rash that stimulates an immune response of natural killer T cells, which scientists think may target and kill developing cancer cells.
It has been hypothesized that the stimulation of this type of immune response may provide protection to certain types of cancer through a process called immunosurveilance.
Danish researchers set out to explore whether people with skin allergies have any special resistance to certain types of cancer. They reviewed the records of 17,000 of people who had been tested for common skin allergens between the years 1984 and 2008. The study was published in the online journal of BMJ on July 11, 2011.
“About one in three (35%) had positive reactions to at least one allergen. Women were more likely than men to have a contact allergy, with 41% testing positive, compared to 26% of men” according to webmd.com (1). It is believed that women tend to have more allergies than men since they wear more jewelry, that often has nickel plating, and use more cosmetics and perfumes.
The researchers found that people who had allergic contact dermatitis had a lower incidence of non-melanoma skin cancer and breast cancer and women had a lower incidence of brain cancer. However, people with contact dermatitis had a higher incidence of bladder cancer. It was hypothesized that since hair dye contains the allergen p-phenylendediamine that exposure to this chemical may increase the risk of this form of cancer.
Skin allergies cause a different immune response in the body than allergies to inhaled substances such as hay fever. Contact dermatitis is considered to be a type 4 response while hay fever causes a type 1 immune response.
"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,” according to Dr. Stanley Fineman, president-elect of the American College of Allergy, Asthma and Immunology.(2)