Exposure of rats to formalin and nitrogen dioxide vapour caused a significant increase in values of the lung wet wt/dry wt ratio (oedema formation) and lipid peroxidation. These effects were not observed in rats treated with short‐term capsaicin, either before or after exposure to the two gases. This protective action of short‐term capsaicin treatment can possibly be linked with the strengthening of the pulmonary antioxidant enzyme defence system by capsaicin. Copyright © 1991 John Wiley & Sons, Ltd.