Grandpa was right: Fresh mountain air does help reduce the coughing, shortness of breath, and chest pain caused by asthma. The folk wisdom was corroborated by a 2006 Swiss study in which researchers reported that a three-week stay in the Alps significantly reduced airway inflammation and improved lung capacity in asthma sufferers.
But that doesn't mean high elevations can't still be risky for some asthmatics. "It's a trade-off between less oxygen and cleaner air," says Erik Swenson, co-author of a spring 2007 review on asthma and altitude published in the European Respiratory Journal. Swenson says the health improvements seen in the Swiss study are probably due to better air quality in the mountains (not the altitude itself), but that the cold, dry air above 5,000 feet can actually trigger asthma attacks in some patients.
Swenson advises hikers with asthma to consult a doctor before high-elevation trips and to carry extra medication.