Should You Avoid Dairy When You Have a Cold?

Chances are at some point you have heard that you should avoid dairy products when you have a cold because milk creates mucus. While this may sound like an old wive's tale, there may be some truth to it. However, science is still inconclusive.

For people with a milk allergy, congestion and increased mucus production is a common reaction. However, for most other people, drinking milk with a cold may only make phlegm feel worse because milk coats the mucus making it feel thicker.

Colds, the flu, and other upper respiratory infections cause a runny nose, congestion, coughing, sore throat, and sometimes fever in response to the virus invading our bodies.

Essentially these symptoms are a defense mechanism—a way that our bodies try to get rid of the virus that is making us sick. Increased mucus production is one way that your body fights infection, and even though it's no fun to deal with, it actually does serve a purpose.

Whether or not drinking milk contributes to congestion is still up for debate. Some early studies designed to test the theory that dairy products increase mucus production found it does not.

One study measured mucus production when people blew their noses into tissues and weighed them and found dairy had no on expelled mucus volume. Another study tested how people felt after drinking either cow's milk or soy milk, and the results were the same. The participants did not know which type of milk they were drinking but reported very similar symptoms.

While both studies concluded that there is no evidence that dairy has an impact on mucus production, newer research suggests otherwise.

A 2019 study found that a dairy-free diet may indeed reduce mucus. Researchers randomly assigned 108 people to either a dairy or dairy-free diet for six days and found self-reported levels of congestion were lower in the dairy-free group.

Other research suggests the effect milk has on mucus production depends on the person’s genetic makeup and the type of dairy protein. The theory is that A1 casein protein, typically found in cow’s milk, stimulates mucus production in the intestines in some individuals, which circulates throughout the body leading to congestion. This research, however, is limited and human studies are needed before concluding a genetic link. 

One of the best things you can do to relieve congestion and excess mucus is to stay hydrated. Drinking water, running a humidifier, using a saline nasal spray, and rinsing sinuses with a Neti Pot can help thin mucus making it easier to expel.

There are also over-the-counter medications like decongestants and expectorants that can help with congestion by breaking up the mucus and allowing it to drain from your sinuses or be expelled through coughing.