I've heard that you shouldn't drink milk when you have a cold because it increases phlegm. Is this true?

Answer From Julie Baughn, M.D.

No. Drinking milk does not cause the body to make phlegm.

Phlegm is thick, sticky mucus that's made in the lungs and upper airways. During a cold, mucus in the nose and throat gets thicker. It contains trapped germs and the proteins and cells the immune system sends to clear out the germs.

There aren't many studies on milk and mucus. But the ones we have suggest that our perceptions can fuel the belief that milk causes more mucus.

In 1948, about 600 people were polled on mucus and milk while seeing their health care provider, mostly for eye problems. The provider tested the mucus of patients who had greater complaints of mucus. Some drank milk and some did not. The conclusion was that milk is not the cause of increased mucus.

More-recent research suggests milk may play a trick on the senses that makes some people think it causes phlegm. When milk and saliva mix in the mouth, they create a somewhat thick liquid that can briefly coat the mouth and throat. The feeling that lingers may be mistaken for extra mucus.

One area that's been studied more is asthma.

Past research shows that children with asthma often stay away from milk because of the notion that it causes more phlegm. But a small study found that kids with asthma had no differences in symptoms whether they drank dairy milk or soy milk.

Reasons not to stop drinking milk

A glass of cold milk or a few bites of frozen yogurt may soothe a sore throat. It also could help you get some nutrients and calories when you might not feel like eating, such as when you're sick.


Julie Baughn, M.D.

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June 13, 2023 See more Expert Answers