In contrast to some earlier reports, allergic conditions appear to increase, rather than decrease, the risk of leukemia and lymphoma, according to a Swedish study.

Depending on the root cause of allergies, theories predict that allergic conditions may either reduce or raise the risk of cancer, researchers explain in the medical journal BMC Public Health.

While several studies have looked at the allergy-cancer relationship by comparing people who have cancer to those who do not, there have been few studies that looked at a representative segment of the general population.

To investigate any connection between allergies and blood cancers, Dr. Karin C. Soderberg, from the Karolinska Institute in Stockholm, and colleagues analyzed data from a group of 16,539 Swedish twins who were born between 1886 and 1925.

The presence of allergic conditions was assessed with questionnaires administered in 1967. The group was followed from 1969 to 1999, and cases of cancer were identified through the Swedish Cancer Registry.

Analysis of the data indicated that hives and asthma appeared to increase the risk of leukemia by 2.1- and 1.6-fold, respectively. Similarly, eczema during childhood was linked to a 2.3-fold higher risk of lymphoma.

As mentioned, the results run counter to past studies, and the team suggests several possible reasons for the disparity. Perhaps new treatments for allergies and asthma also affect the chances developing cancer, for example.

Whatever the reason, they point out that it’s important to clarify “if and how” allergic conditions are connected to blood cancers, since the prevalence of allergies is increasing.

SOURCE: BMC Public Health, November 4, 2004.