Contact allergies, that is the skin rashes and irritations that some people get when they come into contact with certain metals like nickel, or chemicals or other substances like hair dye and latex rubber, may trigger the immune system into defending against some types of cancer, according to new research from Denmark that was published online this week in BMJ Open.

Contact allergies, also known as type IV allergies, are not uncommon, write the authors, who are from the National Allergy Research Centre at Copenhagen University in Hellerup. Estimates suggest about 1 in 5 people will react to one or more chemicals on the European baseline patch test panel.

Previous studies have suggested that people who suffer from type I allergies, the type caused by pollen and house dust mites, may be more or less likely to develop certain cancers.

But we know little about links with type IV allergies, so the authors investigated further by looking at records of the long term health of just under 17,000 adult patients who underwent tests for common allergens between 1984 and 2008 at a specialist skin hospital in Denmark. They then cross-referenced the patients against disease registries, including the Danish Cancer Register.

For their analysis, the authors only included cancer types affecting 40 or more patients.

The results showed that:

  • 35% of the patients tested positive for at least one allergen on at least one diagnosis.
  • More women tested positive than men (41% versus 26%).
  • 19% of the patients had developed at least one growth, including non-cancerous ones.
  • Of those who developed some form of growth, just under 38% had tested positive for contact allergy.
  • Among patients who tested positive for contact allergies, there was a lower rate of breast and non-melanoma skin cancer.
  • And only among women who tested positive for contact allergies, there was a lower rate of brain cancer.
  • However, there was also a higher rate of bladder cancer among patients who tested positive for contact allergies.

The authors concluded that these findings back the theory of “immunosurveillance” which has been around for some time. This hypothesis proposes that people with allergies are less prone to cancer because either the allergic reaction primes the immune system to tackle cancer cells, or it indicates that they have a super-responsive immune system anyway.

They also suggest that the positive link with bladder cancer could be due to “accumulations of chemical metabolites in the bladder”.

They warn against drawing definitive conclusions about these findings at this stage: since these establish only that there is a link and do not prove the existence of cause and effect between contact allergy and cancer.

More analysis is now needed, including that which takes into account environmental factors such as smoking and socioeconomic background, they suggest.

But, if these links do indeed reflect a cause and effect relationship, then “there are implications for understanding how contact allergy can affect cancer development, and vice versa,” they write.

“Association between cancer and contact allergy: a linkage study.”
Kaare Engkilde, Jacob P Thyssen, Torkil Menné, Jeanne D Johansen.
BMJ Open Published Online First 11 July 2011.
Link to Article

Additional source: BMJ Open press release.

Written by: Catharine Paddock, PhD