What REALLY Causes Phlegm?

Close up of woman coughing
Doc: how can I conduct my own test to see what causes excess mucous?

Hi Dr. Jahn,

I have been avoiding certain foods that apparently cause phlegm, but now I want to put them to the test, to see if I REALLY need to avoid them or not. So, I try certain foods and drinks in the morning and, without eating anything else, I will wait to see if I feel a significant increase in phlegm. I just need to know: how long should I wait after eating the test food? In other words, if a substance is going to cause a big increase in phlegm, how long does it take?


Dear Peter,

What you were doing is a common technique in allergy evaluation, called an elimination diet.

I would start by eliminating one class of foods, such as dairy, from your diet. While some people develop excess phlegm shortly after consuming dairy products, I think that giving it two weeks would be a reasonable trial.

You might also want to see an allergist and be tested for specific food groups to guide in your food choices.

Along with your dietary experimentation, please don’t forget to increase your hydration.

Also, irrigate your nose daily with a sinus wash device, such as a Neti pot. Water washes away the potential allergens and also thins out the mucus and makes it less of a nuisance.

– Anthony F. Jahn, MD, FACS, FRCS(C)

This discussion is for general information and not to be construed as specific medical advice that you should obtain from your own physician.

Dr. Jahn is an internationally renowned otolaryngologist based in Manhattan with a sub-specialty interest in the professional voice. His practice includes classical and popular singers. He holds academic appointments at Mount Sinai School of Medicine and Westminster Choir College in Princeton, and is Medical Director at the Metropolitan Opera and Jazz at Lincoln Center. Dr. Jahn has published "The Singer's Guide to Complete Health" (Oxford University Press) - a comprehensive guidebook on a wide range of health issues that affect the voice.