A new study suggests that those who suffer from skin allergies may have a lower risk of skin cancer, and those suffering from other types of allergy may have a reduced cancer risk overall. Conditions such as contact dermatitis can make life miserable for many sufferers who can spend considerable amounts of time identifying skin allergens and working to reduce or eliminate their exposure to them. A study by Danish researchers has identified an association however between contact allergies and cancer risk, although the link is not direct. The connection appears to be due to a physiological phenomenon called immunosurveillance, whereby the body’s immune system is triggered, in this case by allergies, to kill cancer cells before they can cause damage or become more widespread.
Causes of Contact Dermatitis
Contact dermatitis may occur following exposure to certain metals such as nickel or cobalt, with some noticing inflamed, itchy (pruritic) skin, or skin discoloration when wearing certain earrings, rings, or other jewellery. The reaction is often delayed, which can make it difficult to establish the cause of the allergic skin reaction.
Contact dermatitis also occurs when exposed to poison ivy and poison oak, as well as with perfumes, cologne, hair dyes, and make-up for some sufferers. Contact skin allergies stimulate the production of Natural Killer (NK) T-cells, part of the immune system which can seek out and destroy cancer cells. Other allergies, such as to pollen in hayfever sufferers, and to house dust mites, do not appear to stimulate the same response.
Skin allergies have not received much attention in cancer research until now, with Kaare Engkilde, PhD, of Denmark’s National Allergy Research Center, leading a review of nearly 17,000 patients in Denmark who underwent contact allergy testing between 1984 and 2008. Women were more likely than men to experience contact dermatitis with 41% compared to 26% of men testing positive to one or more allergens.
The researchers then checked the Danish health registry to identify the incidence of fifteen different types of cancer and observed lower rates of breast and non-melanoma skin cancers in those with contact dermatitis. There was also a slightly lower risk associated with brain cancer in women, but not with men, who had contact skin allergies.
Some Cancers Increased in Contact Dermatitis Sufferers
The link between cancer and skin allergies is far from straightforward however, with higher rates of bladder cancer in those with skin allergies. The researchers speculate that this could be due to an accumulation of chemical metabolites in the blood, due to the impaired function of the skin barrier to keep out toxins from hair dyes, perfumes, and skin creams, for example, which leads to bladder cancer.
It may also be suggested that those suffering from any potentially chronic skin condition may suffer increased stress and adopt certain unhealthy behaviours to cope with the skin disorder. Similarly, skin diseases may require certain medications that could also increase the risks of cancer when used over long periods of time or when taken incorrectly.
One study looking at the use of methotrexate found an association with liver toxicity, particular in younger female patients, that could then increase the risk of certain cancers in such patients. Methotrexate is prescribed for many patients with psoriasis, contact dermatitis, and other skin conditions, as well as for psoriatic arthritis patients.
Are Cancer Risks Increased by Factors Other than Skin Allergies?
An earlier study carried out in Sweden and published in 2005 (Eriksson, et al) found no significant correlation between atopy and cancer incidence however, with the exception of non-Hodgkins lymphoma cases which were slightly increased in those suffering from contact skin allergies. Other research actually found an increased incidence in some cancer cases in those with atopic dermatitis.
Hagströmer, et al (2005), calculated a 13% increased risk of any cancer developing in those with atopic dermatitis, with oesophageal cancer, pancreatic cancer, brain cancer, and lung cancer incidences most notably increased. Malignant melanoma (skin cancer) did not appear to have an increased risk in those with skin allergies however, although nonmelanoma skin cancer did occur more in atopic patients. This study admitted that the results may have been skewed by an inability to control for confounding variables however, such as the smoking habits of patients.
The association between contact dermatitis and cancer is far from clear, therefore, although the weight of the evidence suggests a possible reduction in the risk of skin cancer for those suffering from skin allergies. More work clearly needs carrying out in this area so as to minimise the risks for all patients, and those with other skin disorders affecting melanin production (vitiligo, for example) need to remain diligent in regards to protecting their skin from sun over-exposure.
The possibility that skin allergies can help fight skin cancer is a welcome one, but it is still a little too early to throw caution to the wind when it comes to skin care. As the researchers themselves admit future studies need to factor in smoking and other factors to give a clearer picture, with the relationship between contact dermatitis and cancers “uncertain and not necessarily the result of causality”.
Holmboe L, Andersen AM, Mørkrid L, Slørdal L, Hall KS., High-dose Methotrexate Chemotherapy: Pharmacokinetics, Folate and Toxicity in Osteosarcoma Patients. Br J Clin Pharmacol. 2011 Jun 27. https://www.ncbi.nlm.nih.gov/pubmed/21707700 [Epub ahead of print]
Hagströmer L, Ye W, Nyrén O, Emtestam L., Incidence of cancer among patients with atopic dermatitis. Arch Dermatol. 2005 Sep;141(9):1123-7. https://www.ncbi.nlm.nih.gov/pubmed/16172309
Eriksson NE, Mikoczy Z, Hagmar L., Cancer incidence in 13811 patients skin tested for allergy. J Investig Allergol Clin Immunol. 2005;15(3):161-6. https://www.ncbi.nlm.nih.gov/pubmed/16261950