July 20, 2011 — Contact allergies might offer protection against some cancers, according to Danish researchers.
In both men and women, they found an inverse association between contact allergy and nonmelanoma skin cancer and breast cancer. An inverse trend for brain cancer was found in women with contact allergy.
However, the authors also identified a positive association between contact allergy and bladder cancer.
The inverse associations lend support to the theory of immunosurveillance, in that allergic symptoms are the adverse effect of hyperimmunity, according to the report, published online July 11 in BMJ Open.
The reason for these associations remains unclear and is not necessarily the result of causality. "Our study is explorative, and it is difficult to directly advise clinicians based on a single study," said lead author Kaare Engkilde, PhD, a postdoctoral researcher at the National Allergy Research Center, Copenhagen, Denmark.
"I would not recommend fewer screenings for breast cancer, nonmelanoma skin cancer, or brain cancer, although it's intriguing that such associations appear, and should lead to further studies," he told Medscape Medical News. "These would probably be done in mice, as it would be difficult to do further database studies to show causation."
Showing causation might be more applicable for bladder cancer, he noted, because a positive association was found, "although we lacked the power to see if this association is due to a specific allergen/hapten," said Dr. Engkilde.
Interpret With Caution
"The study is intriguing, and adds to the medical literature suggesting that immunologic stimulation, such as with an allergic reaction, could potentially reduce the risk of cancer," said Stanley Fineman, MD, president-elect of the American College of Allergy, Asthma and Immunology.
"At this time, one should interpret the conclusions of this study with caution; I doubt that there is truly a causal effect," he told Medscape Medical News.
The authors point out that if the relationships between contact allergy and cancer development observed in the study are etiologic, there are clinical implications; however, those clinical implications remain unclear.
"We have made great progress in the last few decades in our understanding of allergic and immunologic mechanisms," said Dr. Fineman. "This knowledge has helped direct therapy for patients with allergies. I don't think we can make any assumption about potential prevention or treatment of cancers related to contact allergies at this time."
Allergies and Cancer Risk
Contact allergy is a prevalent disorder, affecting about 20% of the general population in Denmark, the authors note. It is caused by skin contact with low-molecular-weight nonprotein chemicals or haptens, and can progress to allergic contact dermatitis if subsequent reexposure exceeds the individual's threshold.
A number of studies have investigated associations between allergic disorders and cancer. Although results have been inconsistent, most epidemiologic studies suggest that atopic diseases are associated with a reduced risk for cancer, the authors point out. As previously reported by Medscape Medical News, one study found a reduced risk for cervical and ovarian cancers among women who had hay fever or asthma.
"Our findings come from an observational study, and we can't explain the mechanism of the associations," senior author Zuber Mulla, DO, told Medscape Medical News at that time. "We do know that cytokines, which are elevated in allergic conditions, might have a cancer-protective effect."
Another study found that allergies appear to be protective against glioma, and that the risk for the disease was inversely associated with the total number of different allergy types and with the number of allergies for each allergy type.
Few studies, however, have evaluated the association between cancer and contact allergy, a type IV allergy.
Inversely and Significantly Associated
Using patient registries, Dr. Engkilde and colleagues identified 16,922 individuals with dermatitis who had undergone patch tests for contact allergy from November 1984 to December 2008. Of this group, 6,065 (35.8%) had a positive reaction to at least 1 allergen on at least 1 occasion. The authors note that the prevalence of contact allergy was higher in women than in men (41.4% vs 26.1%).
The data were linked to the Danish Cancer Registry, and 3,200 patients (18.9%) with dermatitis were identified with a benign tumor and/or a malignant cancer diagnosis; 1,207 (37.7%) of these also had a positive patch test reaction.
Their crude data analysis revealed a "positive and significant association" between contact allergy and being registered in the cancer registry (odds ratio [OR], 1.1; P = .014). The ORs for different cancer groups were calculated using logistic regression analyses, after adjustment for sex and age.
Breast cancer (OR, 0.80; P = .031) and nonmelanoma skin cancer (OR, 0.83; P = .021) in both sexes were found to be inversely and significantly associated with contact allergy. Bladder cancer was found to be positively and significantly associated with contact allergy (OR, 1.44; P = .040).
The authors also investigated various interaction terms between cancer subtypes and sex, and found a significant interaction term only for brain/central nervous system (CNS) cancer. When they conducted a subsequent adjusted regression analysis in women with dermatitis, a trend toward an inverse association was observed between brain/CNS cancer and contact allergy (OR, 0.36; P = .080).
Further analyses, adjusted for environmental factors such as smoking and socioeconomic background, are needed to understand the role of contact allergies in the development of cancer, they conclude.
"However, if these relations are etiological, there are implications for understanding how contact allergy can affect cancer development and vice versa," the authors write.
Financial support was received from Aage Bang's Foundation and the Capital Region's Research Foundation. The authors have disclosed no relevant financial relationships.
BMJ Open. Published online July 11, 2011. Full text
In both men and women, they found an inverse association between contact allergy and nonmelanoma skin cancer and breast cancer. An inverse trend for brain cancer was found in women with contact allergy.
However, the authors also identified a positive association between contact allergy and bladder cancer.
The inverse associations lend support to the theory of immunosurveillance, in that allergic symptoms are the adverse effect of hyperimmunity, according to the report, published online July 11 in BMJ Open.
The reason for these associations remains unclear and is not necessarily the result of causality. "Our study is explorative, and it is difficult to directly advise clinicians based on a single study," said lead author Kaare Engkilde, PhD, a postdoctoral researcher at the National Allergy Research Center, Copenhagen, Denmark.
"I would not recommend fewer screenings for breast cancer, nonmelanoma skin cancer, or brain cancer, although it's intriguing that such associations appear, and should lead to further studies," he told Medscape Medical News. "These would probably be done in mice, as it would be difficult to do further database studies to show causation."
Showing causation might be more applicable for bladder cancer, he noted, because a positive association was found, "although we lacked the power to see if this association is due to a specific allergen/hapten," said Dr. Engkilde.
Interpret With Caution
"The study is intriguing, and adds to the medical literature suggesting that immunologic stimulation, such as with an allergic reaction, could potentially reduce the risk of cancer," said Stanley Fineman, MD, president-elect of the American College of Allergy, Asthma and Immunology.
"At this time, one should interpret the conclusions of this study with caution; I doubt that there is truly a causal effect," he told Medscape Medical News.
The authors point out that if the relationships between contact allergy and cancer development observed in the study are etiologic, there are clinical implications; however, those clinical implications remain unclear.
"We have made great progress in the last few decades in our understanding of allergic and immunologic mechanisms," said Dr. Fineman. "This knowledge has helped direct therapy for patients with allergies. I don't think we can make any assumption about potential prevention or treatment of cancers related to contact allergies at this time."
Allergies and Cancer Risk
Contact allergy is a prevalent disorder, affecting about 20% of the general population in Denmark, the authors note. It is caused by skin contact with low-molecular-weight nonprotein chemicals or haptens, and can progress to allergic contact dermatitis if subsequent reexposure exceeds the individual's threshold.
A number of studies have investigated associations between allergic disorders and cancer. Although results have been inconsistent, most epidemiologic studies suggest that atopic diseases are associated with a reduced risk for cancer, the authors point out. As previously reported by Medscape Medical News, one study found a reduced risk for cervical and ovarian cancers among women who had hay fever or asthma.
"Our findings come from an observational study, and we can't explain the mechanism of the associations," senior author Zuber Mulla, DO, told Medscape Medical News at that time. "We do know that cytokines, which are elevated in allergic conditions, might have a cancer-protective effect."
Another study found that allergies appear to be protective against glioma, and that the risk for the disease was inversely associated with the total number of different allergy types and with the number of allergies for each allergy type.
Few studies, however, have evaluated the association between cancer and contact allergy, a type IV allergy.
Inversely and Significantly Associated
Using patient registries, Dr. Engkilde and colleagues identified 16,922 individuals with dermatitis who had undergone patch tests for contact allergy from November 1984 to December 2008. Of this group, 6,065 (35.8%) had a positive reaction to at least 1 allergen on at least 1 occasion. The authors note that the prevalence of contact allergy was higher in women than in men (41.4% vs 26.1%).
The data were linked to the Danish Cancer Registry, and 3,200 patients (18.9%) with dermatitis were identified with a benign tumor and/or a malignant cancer diagnosis; 1,207 (37.7%) of these also had a positive patch test reaction.
Their crude data analysis revealed a "positive and significant association" between contact allergy and being registered in the cancer registry (odds ratio [OR], 1.1; P = .014). The ORs for different cancer groups were calculated using logistic regression analyses, after adjustment for sex and age.
Breast cancer (OR, 0.80; P = .031) and nonmelanoma skin cancer (OR, 0.83; P = .021) in both sexes were found to be inversely and significantly associated with contact allergy. Bladder cancer was found to be positively and significantly associated with contact allergy (OR, 1.44; P = .040).
The authors also investigated various interaction terms between cancer subtypes and sex, and found a significant interaction term only for brain/central nervous system (CNS) cancer. When they conducted a subsequent adjusted regression analysis in women with dermatitis, a trend toward an inverse association was observed between brain/CNS cancer and contact allergy (OR, 0.36; P = .080).
Further analyses, adjusted for environmental factors such as smoking and socioeconomic background, are needed to understand the role of contact allergies in the development of cancer, they conclude.
"However, if these relations are etiological, there are implications for understanding how contact allergy can affect cancer development and vice versa," the authors write.
Financial support was received from Aage Bang's Foundation and the Capital Region's Research Foundation. The authors have disclosed no relevant financial relationships.
BMJ Open. Published online July 11, 2011. Full text
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