I must congratulate Padmaja Subbarao and colleagues for their elegant review, Asthma: epidemiology, etiology and risk factors 1. But they missed covering acetaminophen as an etiological cause of asthma in both adults and children. Several studies have shown a relationship between acetaminophen consumption and presence of asthma. For example, Cohet and colleagues 2 studied the association between infections in children aged 0 to 4 years and medications used (antibiotics and acetaminophen) and the subsequent presentation of asthma at age 6 to 7; the authors observed that the use of acetaminophen in the first year of life was weakly associated with wheezing, asthma, rhinitis, and eczema. In their prospective study, Barr and colleagues 3 found that acetaminophen use was associated with the presence of newly diagnosed asthma among women. Several mechanisms have been postulated that may explain the possible risk of asthma with acetaminophen use. The main mechanism involves glutathione, which is a potent antioxidant found in lung tissue. Acetaminophen has shown to lower serum glutathione levels in healthy volunteers. 4 A second possible mechanism is thought to be acetaminophen’s lack of inhibition of the enzyme cyclooxygeanse, the key enzyme involved in the production of prostaglandins playing a major role in the inflammatory cascade in asthma. 5 Finally, an emerging hypothesis involves the possible antigenic effect of acetaminophen and subsequent rise in IgE and histamine levels with exposure to acetaminophen. 6
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For the full letter, go to: www.cmaj.ca/cgi/eletters/cmaj.080612v1#201684