A Answers (2)
Paul Ehrlich, MD, Allergy & Immunology, answeredContrary to conventional wisdom, steam and vaporizers are not usually very helpful in asthma attacks, since the large water droplets they form will not reach the lower airways where mucus creates the biggest problems.
Steam or a vaporizer can help liquefy mucus when breathing problems are due to a cold or allergy. This often makes a person feel better. The viral condition, croup, is well known for responding to humidity. Asthma, on the other hand, is caused by an overreaction of the airways, making them collapse or pinch off air flow. For this reason, steam or vaporizers occasionally add to the irritation and worsen the breathing problem.