Does milk increase mucus production, and should it be avoided when you have a cold?

The claim that milk promotes mucus secretion is very widespread and has remained uncontested for a long time. Therefore a number of studies have been carried out to test this hypothesis. It should be noted, however, that these studies largely date back to the 90s and, at most, the early 2000s. More recent publications on this topic are review articles that re-examine the findings of these existing studies.

So what does the research say? Does milk indeed increase mucus secretion?

Current scientific evidence shows quite clearly - more clearly than is the case of many other theories - that drinking cow's milk does NOT increase mucus production. This has been established independently in several studies [1-4]. Whether compared with control groups of peope, who either did not drink any milk, drank soymilk, or simply consumed smaller quantities of milk, all findings consistently showed that there was no discernible difference in the mucus production between the two groups [1].

What was already evident, however, was the sensation of increased or thicker mucus in the throat [1-3]. Numerous explanations have been suggested for this phenomenon. For one, milk is what is known in Chemistry as an emulsion, i.e. a solution in which fat and water are homogeneously mixed. This emulsion can mix with the saliva in our mouth, thereby creating the sensation that more mucus has been produced. On the other hand, consuming milk - just like drinking water - stimulates the production of more saliva, which also contains small amounts of mucus and further intensifies this sensation of tightness and mucus build-up [3]. So, it is not the production of more mucus due to milk consumption, but the feeling that is created in the mouth from the interaction between the emulsion and our saliva, that could be the reason for this myth.

Furthermore, the mind could also plays a role in this case. Whilst, objectively speaking, there are no significant changes in mucus production, the subjective experience may well differ [2]. In a study carried out in Australia, researchers noted that people who believed this claim reported more severe symptoms immediately after consumption than those who did not believe it. However, after 4 and 24 hours respectively, no further differences were observed. Nor were any significant increases in mucus production, inflammation markers or cold symptoms detected when compared with soy milk [1].

What does this mean for us, milk-drinkers?

In short: we no longer need to worry that we will choke on our well-deserved glass of milk in the midst of a cold. It is indeed more likely that our brain is the main culprit behind our misleading belief.

References:

[1]	Balfour-Lynn I. M., 2019, Milk, mucus and myths, Archives of Disease in Childhood, 104(1), 91–93.
[2]	Wüthrich B., Schmid A., Walther B., & Sieber R., 2005, Milk consumption does not lead to mucus production or occurrence of asthma. Journal of the American College of Nutrition, 24(6 Suppl.), 547S–555S.
[3]	Zaitlin P., Dwyer J., Gleason G. R., 2013, Mistaken Beliefs and Facts About Milk and Dairy Foods, Wolter Kluwer Health | Lippincott Williams & Wilkins, Volume 48, Number 3
[4]	Fachgesellschaft für Ernährungstherapie und Prävention (FET), Mythen im Faktencheck: Milch & Gesundheit, 3.4.2026, Website: https://fet-ev.eu/kurzprofil/faktencheck-milch-gesundheit/