In analogy with findings from animal experiments, people with low glutathione‐peroxidase (GSH‐Px) activity could be expected to have altered sensitivities to effects of drugs, chemicals and possibly food. We have investigated GSH‐Px activity in 12 patients with intrinsic asthma and food and aspirin intolerance. Ten of the 12 patients had very low or low GSH‐Px activity and the frequency of low GSH‐Px activity in this group was statistically significant (P<0.001) compared with the control material of age‐ and sex‐matched healthy individuals. Our finding of lowered GSH‐Px activity in patients with aspirin intolerance may indicate the involvement of hitherto unknown mechanisms in the pathogenesis of asth