Contact allergy can activate the immune system to fight cancer.

Contact allergy (reactions caused by direct contact with materials such as conventional metals or chemicals) may help the immune system to prevent certain types of cancer. Previous studies have shown that people with high sensitivity to pollen, mites, house dust, may be more or less likely to develop cancer.
The authors base their findings on just under 17,000 Danish adults all of whom were tested for a positive response on the most common contact allergens between 1984 and 2008.
All studies were recorded in a special register.
Overall, slightly more than one-third (35%; 6065) were subjected to stimulation for at least one allergen.
Most of the exposure to allergens were women, slightly more than 41% of them "react", compared with about one in four (26%) male.
Conducted the study group of 40 people.
It was seen lower rates of breast cancer and melanoma (skin cancer) in both sexes among those who have a contact allergy, as well as lower rates of brain cancer in women.
These findings state that people with allergies are less likely to get cancer because their immune system has a strong reaction to stimuli.
The analysis also showed higher rates of bladder cancer among those who have a contact allergy, which can cause higher levels of metabolites accumulate in the blood.
The authors warn that too early to draw definitive conclusions about cause and effect. Further analysis will be carried out taking into account influential factors, such as smoking and social class. The obtained results can bring much closer scientists to answer this question