E-cigarette use has grown exponentially in recent years, but little is known about its health effects.

A new study from the American College of Chest Physicians found that the single use of an e-cigarette approximating the nicotine exposure of one tobacco cigarette reduces the sensitivity of the cough reflex.

For the study, researchers collected and analyzed data from 30 adult lifetime nonsmokers with no history of asthma or respiratory diseases and used cough tests to determine how e-cigarettes affect the cough reflex.

They used Capsaicin, the pungent extract of red peppers, to induce a safe cough in the subjects and establish their baseline cough reflex sensitivity prior to use of electronic cigarette. Each subject then inhaled 30 puffs of an electronic cigarette, which contains nicotine in a vehicle of distilled water. Fifteen minutes after the e-cigarette "vaping" session, subjects were tested again using the capsaicin cough challenge and then tested again after 24 hours. Based on a comparison of results, a significant decrease in cough reflex sensitivity was shown within the subjects as compared with their baseline levels.

Researchers found that nicotine is probably responsible for the effect on the cough reflex.

Previous studies have shown that nicotine also promotes cough immediately after ingestion, suggesting that nicotine has a dual action: an immediate stimulation of the cough reflex and a delayed inhibition.

The findings are detailed in the journal CHEST.