Smoking and HP

Q: Smoking ____________ the risk of Hypersensitivity pneumonitis (HP)? (select one)

A) decreases

B) increases

Answer: A

This is one of the paradoxes of medicine. Hypersensitivity pneumonitis is also known as extrinsic allergic alveolitis. Interestingly, and hard to explain, cigarette smoking decreases the risk of HP. Smokers are less likely to develop different forms of HP, such as farmer's lungs, pigeon breeder's disease, HP-associated contaminated air conditioners, and Japanese summer-type HP. 

Said that once the disease is established, smoking turns it into a more chronic and severe course.

One possible explanation is smokers' diminished antibody responses to inhaled antigens despite similar exposure.

#pulmonary

References:

1. Arima K, Ando M, Ito K, et al. Effect of cigarette smoking on prevalence of summer-type hypersensitivity pneumonitis caused by Trichosporon cutaneum. Arch Environ Health 1992; 47:274.

2. McSharry C, Banham SW, Boyd G. Effect of cigarette smoking on the antibody response to inhaled antigens and the prevalence of extrinsic allergic alveolitis among pigeon breeders. Clin Allergy 1985; 15:487.

3. Ohtsuka Y, Munakata M, Tanimura K, et al. Smoking promotes insidious and chronic farmer's lung disease, and deteriorates the clinical outcome. Intern Med 1995; 34:966.