Imamura and colleagues1 found that pravastatin attenuated allergic airway inflammation through suppression of interleukin 17 in the lungs of ovalbumin-sensitised mice. However, in the accompanying editorial,2 Rubin pointed out that, in clinical practice, it is unlikely that adding a statin to an appropriate dose of inhaled corticosteroids might provide any additional benefit for patients with asthma, highlighting that in this setting statin therapy can represent a “snake oil panacea”. We concur with Rubin,2 and further suggest that statin drugs might actually be harmful in patients with asthma.

In healthy individuals, immune responses to allergens include a dominant regulatory element. There is mounting evidence that the function of regulatory T cells (Tregs) may be defective in patients with allergy and asthma.3 Indeed, as Imamura and colleagues reported,1 there is a reciprocal developmental pathway for the generation of pathogenic Th17 cells and protective Tregs in the immune system, depending on the state of the innate immune system.

On the other hand, some of the well-known immunomodulatory effects of statins are mediated through an increase in the peripheral numbers and functionality of Tregs4 by the induction of the transcription factor forkhead box P3. However, an increase in Treg numbers and functionality may impair the host antitumour immunity via the suppression of tumour-specific effector T cell responses and the development of immune tolerance to neoplastic cells.4

Interestingly, epidemiological evidence suggests that a history of allergy is associated with a decreased overall risk of cancer.5 It is plausible that the defective function of Tregs in subjects with allergic disease could reduce the cancer risk by enhancing the ability of the immune system to detect and remove malignant cells.

We therefore feel that caution is warranted when treating patients with asthma with statins; in some cases these drugs can represent more a poison than a snake oil.