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02-08-2011 | Immunology | Article

Contact allergy linked to reduced risk for some cancers

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MedWire News: Individuals with allergies to metal and chemicals have a reduced likelihood of developing certain types of cancer, results from a Danish study suggest.

However, the findings are not conclusive and need to be clarified in future studies, say the researchers.

Writing in the journal BMJ Open, Kaare Engkilde (University Hospital Gentofte, Hellerup, Denmark) and colleagues explain that previous research has indicated that people who are allergic to substances such as pollen and house dust mites may have a below-average risk for developing cancer.

But they add that it is not known whether individuals with contact allergies to common metals and chemicals might also be protected against the disease.

To investigate, the researchers studied data on 16,922 Danish adults with dermatitis for the period 1984-2008. Of these,6065 (35.8%) were diagnosed with contact allergy.

Linkage with the Danish Cancer Registry revealed that 3200 (18.9%) of these dermatitis patients were diagnosed with cancer during the study period.

The researchers found that patients with contact allergy were significantly less likely to develop certain types of cancer than those without contact allergy.

Specifically, contact allergy patients of both genders were 17% less likely to develop non-melanoma skin cancer and 20% less likely to develop breast cancer than those without contact allergy, after accounting for age.

Among women, there was a trend toward a reduced risk for brain/CNS cancer among those with contact allergy (odds ratio=0.36).

However, patients with contact allergy were 44% more likely to develop bladder cancer than those without, the researchers note.

They speculate that this increased risk for bladder cancer associated with contact allergy may be due to high accumulated concentrations of chemical metabolites.

Engkilde and team conclude: "Contact allergy was found to be associated with four different cancer subtypes. Most of the associations were inverse."

They add: "The reason for these relations is uncertain and not necessarily the result of causality. More refined analyses, adjusting for social class and smoking, for instance, and studies focusing on specific chemical exposures are required to further our understanding of the role of contact allergies in the development of cancer."

By MedWire Reporters

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