This article is from the Asthma FAQ, by Patricia Wrean and Marie Goldenberg email@example.com with numerous contributions by others.
Thrush, or thrush mouth, is the popular term for a yeast
infection (candida albicans) in the back of throat. The major
symptom of thrush is a white film located at the back of the
throat and tonsil area. It is usually cured by the use of an
Thrush is a very common side effect of taking inhaled
corticosteroids, since steroids alter the local bacteria and
fungal population of the mouth, enhancing fungal growth. The
way to avoid this complication is to ensure that the back of
the throat doesn't remain coated with corticosteroid after use
of the inhaler, either by using a spacer or by rinsing the mouth
very thoroughly afterwards. Unfortunately, some people still
get it even when they are very thorough about rinsing.