Coffee is not recommended for treating asthma even though it contains caffeine, a central nervous system stimulant and weak bronchodilator that also reduces respiratory muscle fatigue. Caffeine is chemically similar to theophylline, an older medication for the treatment of asthma, and can help to open up the airways and improve lung function. In one small study caffeine even showed potential in the prevention of exercise-induced asthma when given at moderate to high doses. However, it is not a replacement for approved treatments, such as an albuterol inhaler. The dose of caffeine required to really help in the treatment of asthma is likely to be so high that the side effects, which can include an increased heart rate, headache, difficulty sleeping, nervousness and agitation, outweigh the benefits.

It is also recommended that caffeine be avoided for up to 4 hours before a lung function test, because it might make your lung function appear better than it actually is.

In addition to coffee, caffeine is also found in a variety of drinks (tea, cola, cocoa and energy drinks), botanical sources (including kola nuts, guarana and yerba mate) and over-the-counter medications, such as NoDoz.