Well maybe... According to a May 2010 study where questionnaire-based interviews were performed and encompassed self-reported history of prior medical diagnosis of asthma and eczema, medication use, and several covariates among 3,300 cancer cases and 512 population controls, a history of asthma was negatively associated with all cancer types combined (OR, 0.72; 95% CI, 0.5-1.1) and similarly for a history of eczema (OR, 0.66; 95% CI, 0.4-1.1).Why would this happen? Well, allergies is due to a hyperreactive immune system that may lead to a more efficient elimination of abnormal cells, thus lowering cancer risks.
More study is needed to verify if this correlation truly exists.
What I would like to see is 3 groups (allergic group treated with meds only, allergic group on immunotherapy, and control group) followed out.
Reference:
History of asthma or eczema and cancer risk among men: a population-based case-control study in Montreal, Quebec, Canada. Ann Allergy Asthma Immunol. 2010 May;104(5):378-84.