Does milk really make your body produce more mucus—or is that just an old health myth that refuses to die? For generations, people have claimed that drinking milk worsens congestion, especially when they’re sick, while many doctors have brushed the idea aside as imagination. But now, new research is reopening the debate in a surprising way.
Key Takeaways
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New evidence suggests milk may increase mucus in some individuals, especially during respiratory illness.
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Experts remain divided, with some attributing symptoms to perception rather than physiology.
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Your body matters most—gut health, inflammation, and milk type (A1 vs A2) may determine your response.
The Truth About Milk and Mucous
The 12th-century Jewish physician Maimonides is perhaps best remembered for his advice to enjoy a bowl of chicken soup to fight off a cold. Modern science supports his idea. Chicken soup has anti-inflammatory and other symptom-easing properties.
But he also made another statement that's been passed down through the generations. He said milk causes "a stuffing in the head."
Although not as famous as the chicken soup remedy, apparently, word got around. I’ve met any number of people who think milk makes their sinus problems worse.
Most scientists didn’t buy into it -- until now.
A new study suggests that milk increases mucus production, worsens cold symptoms, and should be avoided by those with respiratory infections.
Let’s take a look. . .
Skeptical Doctor Surprised
The randomized, double-blind study published in the journal Laryngoscope in September was carried out by Adam Frosh and colleagues at the Department of Ear, Nose, and Throat Surgery, Lister Hospital, Stevenage, England.
Dr. Frosh explains his reason for exploring the milk-mucus link like this: "I was skeptical and didn’t believe it was real [but] I have been asked about it by so many patients over the years that I felt I needed to look into it — if only to put the idea to rest."
So the research team recruited 26 men and 82 women who suffered with persistent increased mucus secretions in the head and upper body.
All were put on a dairy-free diet for six days. On days three to six, half drank 12 ounces of full-fat cow's milk while the other half drank the same amount of soya milk. Both drinks were flavored so they tasted exactly the same.
Everyone self-reported less mucus in the first two days. But over the next four days the soya group experienced a continuing reduction in symptoms, while a significant increase in mucus was described by the cow's milk group.
Commenting on the findings, Dr. Frosh said, "The results were the opposite of what I was expecting. This was quite a big effect in a relatively short space of time. It’s reasonable to conclude that anyone who feels milk increases their mucus production should consider reducing their dairy intake, or try a dairy-free diet, to see if it improves their symptoms."
It's All a Myth
One doctor who remains unconvinced is children's respiratory consultant Ian Balfour-Lynn from Royal Brompton Hospital, London.
He carried out an extensive review of existing research that was published in Archives of Disease in Childhood in the same month as the Lister Hospital study. He wrote, "[T]here is no evidence...that milk leads to excessive mucus secretion...The milk–mucus myth needs to be rebutted firmly.”
Dr. Balfour-Lynn believes the texture of milk -- an emulsion of fat in water -- makes people feel their saliva is thicker and harder to swallow, and it leaves an after-feel because small amounts remain in the mouth. This gives the impression of greater mucus.
So is the effect real, as supported by Dr. Frosh's study, or imaginary, which is Dr. Balfour-Lynn's strong view? Perhaps the answer lies elsewhere.
Not all Milk is The Same
The milk almost everyone drinks is A1, derived from Holsteins and Friesian breeds. An opioid derived from the breakdown of A1, called BCM-7, should stimulate mucus production in the gut, but not elsewhere in the body.
However, BCM-7 may also create mucus in the respiratory system if two conditions are present at the same time. First, if the gut is leaky, allowing BCM-7 to be absorbed into the bloodstream, and second, if inflammation is already present in the respiratory organs.
So the observation dating from the Middle Ages is at least partly correct. Milk will create mucus and worsen symptoms in some people with colds, but it depends on the gut and respiratory health of the individual and the type of milk consumed.
Those who want to drink milk without BCM-7 can do so by buying sheep and goat milk. Alternatively, it may be possible to find A2 milk from older cow breeds. Here, BCM-7 remains tightly bound, preventing its release in the gut.
Summary
A long-standing belief that milk worsens mucus and cold symptoms is gaining new attention from modern research. A recent randomized, double-blind study found that participants consuming cow’s milk experienced increased mucus compared to those drinking soy milk. However, not all experts agree, with some arguing the effect is merely perceived due to milk’s texture. Emerging insights suggest the truth may lie in individual biology—specifically gut health, inflammation levels, and the type of milk consumed. Certain milk proteins, like BCM-7 found in A1 milk, may contribute to mucus production in some people, while alternatives like goat, sheep, or A2 milk may not have the same effect.
Frequently Asked Questions
Does milk really increase mucus production?
Some newer research suggests milk may increase mucus in certain people, but the evidence is still mixed and debated among experts.
Why do some people feel more congested after drinking milk?
It may be due to milk’s texture creating a thicker sensation—or, in some cases, a real biological response depending on individual health factors.
Does this happen to everyone?
No. Responses appear to vary widely based on factors like gut health, inflammation, and individual sensitivity to certain milk proteins.
Are all types of milk the same in this effect?
Not necessarily. A1 milk may behave differently than A2, goat, or sheep milk, which may be less likely to trigger symptoms in some individuals.
Should I avoid milk when I have a cold or sinus issues?
If you notice increased congestion after consuming dairy, it may be worth reducing or eliminating it temporarily to see if symptoms improve.
