Fact vs. Myth: What Does Dairy Do to You When Sick?

November 14, 2025 •

4 min read

For centuries, people have believed that dairy increases mucus production when sick, but science debunks this popular myth. So, what does dairy do to you when sick, and should you avoid it?

Quick Summary

Scientific research shows dairy does not increase mucus production during illness. It provides valuable nutrients and fluids crucial for recovery, though individual sensitivity and perception can vary.

Key Points

Mucus Myth Debunked: Scientific studies have repeatedly shown that dairy products do not increase mucus production during a cold or illness.
Perception vs. Reality: The sensation of thicker mucus is likely due to dairy's creamy texture mixing with saliva, which can temporarily coat the throat.
Nutrient-Rich Support: Dairy is a source of protein, Vitamin D, Zinc, and Selenium, which provide valuable nutritional support for the immune system when you're sick and have a low appetite.
Probiotics for Gut Health: Fermented dairy, like yogurt and kefir, contains probiotics that support the gut microbiome, which is vital for a healthy immune response.
Lactose Intolerance Alert: If you have lactose intolerance, a stomach bug can temporarily worsen symptoms. In this case, avoiding dairy may prevent digestive discomfort.
Allergy Considerations: Individuals with a confirmed dairy allergy must avoid dairy, as it can cause an immune reaction that affects respiratory symptoms.
Individual Comfort Matters: Ultimately, if dairy makes you feel uncomfortable, regardless of the reason, it is best to opt for alternatives like broth or plant-based milks.

The persistent mucus myth: What science says

The belief that dairy products like milk and cheese cause or increase mucus production during a cold is a widespread misconception that has lingered for centuries. Numerous scientific studies, however, have repeatedly failed to find any conclusive link between dairy consumption and increased mucus secretion or worsened respiratory symptoms. A controlled study published in the American Review of Respiratory Disease found no difference in the amount of nasal mucus produced in volunteers with a cold who drank milk compared to those who did not. This evidence confirms that for the average person, dairy does not exacerbate mucus-related illness symptoms.

Why does dairy feel like it creates more mucus?

The sensation of increased phlegm or thickness in the throat after consuming dairy is a common experience, but it's more about perception than reality. This feeling is caused by the creamy emulsion of milk mixing with saliva, temporarily coating the mouth and throat. The resulting thicker liquid can feel like excess mucus, especially when your respiratory tract is already irritated from an illness. A placebo-controlled study demonstrated that participants who believed they were drinking milk reported similar sensations of thicker mucus, highlighting the psychological aspect of this perception. Your brain associates the creamy texture with phlegm, even when no extra mucus is being produced.

The immune-boosting benefits of dairy when sick

Far from being harmful, consuming dairy products when sick can provide valuable nutritional support for your body as it fights off an infection. When you're ill, your appetite often decreases, making it harder to get the necessary calories and nutrients for a speedy recovery. Dairy offers a dense source of these crucial components.

Key nutrients in dairy that support immune function

Protein: Essential for building and repairing body tissues and creating antibodies to fight off pathogens.
Vitamin D: Plays a vital role in regulating the immune system and helping white blood cells combat infection. Fortified milk is a common source.
Probiotics: Found in fermented dairy products like yogurt and kefir, these beneficial bacteria support gut health. Since up to 70% of the immune system resides in the gut, a healthy microbiome is crucial for a strong immune response.
Zinc and Selenium: These minerals are important for the function of immune cells and reducing inflammation.
Calcium: Aids in cellular function and overall health during illness.

For a sore throat, cold dairy products like frozen yogurt or ice cream can be soothing, while a warm glass of milk can provide comfort and hydration.

Table: Dairy vs. Alternatives when feeling ill


Feature	Dairy Products	Dairy Alternatives (e.g., Fortified Plant Milks)
Mucus Production	Does not increase mucus. May cause a temporary sensation of thickness due to texture.	No effect on mucus. Does not create the same creamy mouthfeel.
Immune Support	Excellent source of protein, Vitamin D, Zinc, and probiotics (in yogurt/kefir).	Can be fortified with comparable nutrients like Calcium and Vitamin D. Protein content varies (soy is often highest).
Sore Throat Relief	Can be very soothing. Cold ice cream or warm milk can provide comfort.	Soothing options like warm herbal tea or smoothies are good substitutes.
Lactose Intolerance	Can cause digestive discomfort (gas, bloating, diarrhea), which may worsen if temporary intolerance occurs due to a virus.	Naturally lactose-free. Safe for those with lactose intolerance.
Allergies	Avoid if you have a cow's milk allergy, as this can cause immune reactions and exacerbate respiratory symptoms.	Safe for those with a dairy allergy, but check for other allergens like soy or nuts.

Considerations for individuals with allergies or intolerance

While the mucus myth is debunked for most people, it's important to listen to your body, especially if you have a specific condition. If you have a confirmed cow's milk allergy, you must avoid all dairy products, as consuming them can trigger an immune response with serious symptoms. For those with lactose intolerance, consuming dairy when sick, especially with a stomach bug, can exacerbate digestive symptoms like bloating, gas, and diarrhea. In some cases, a viral infection can even cause temporary lactose intolerance by damaging the intestinal lining, reducing the enzyme needed to digest lactose. If you find that dairy consistently makes you feel worse, whether from perception or a genuine issue, it is perfectly fine to switch to alternatives like broths or fortified plant-based milks. The key is to stay hydrated and nourished.

Conclusion

Dispelling the myth that dairy makes you sicker is crucial for informed health decisions during illness. For most people, dairy products are a safe and nutritious choice when unwell, providing essential proteins, vitamins, and minerals that support the immune system and aid recovery. While the creamy texture might temporarily feel like increased congestion, this is not based on actual mucus production. However, those with a genuine dairy allergy or lactose intolerance should exercise caution or opt for alternatives. Ultimately, the best approach is to listen to your body and choose foods that provide comfort and sustenance as you recover. For more information on general cold remedies and food choices, consult authoritative sources such as Mayo Clinic's expert advice on cold symptoms.

Frequently Asked Questions

No, numerous scientific studies have debunked the myth that milk increases phlegm or mucus production. The creamy texture can create a temporary sensation of thickness in the throat, which some people mistake for excess mucus.

For most people, it is not bad to drink milk with a cold. It can provide essential nutrients like protein and Vitamin D, which are important for recovery, especially when you have a reduced appetite. The discomfort is often more a matter of perception.

Yes, yogurt can be beneficial when you're sick. It provides protein, and certain yogurts with 'live active cultures' contain probiotics that support gut health and, by extension, your immune system.

Yes, cold dairy items like ice cream or frozen yogurt can be very soothing for a sore throat, providing comfort and helping you get calories and nutrients when it's painful to swallow solid food.

Yes, a viral gastrointestinal infection can temporarily damage the intestinal lining, leading to a reduced production of the enzyme lactase. This can cause temporary lactose intolerance, resulting in worsened digestive symptoms if dairy is consumed.

If you consistently feel congested after drinking milk, it may be a subjective sensation caused by the creamy texture. However, it's also possible that you have an undiagnosed sensitivity or intolerance. Listening to your body and switching to alternatives if you feel uncomfortable is a valid choice.

If you prefer to avoid dairy, good alternatives include hydrating beverages like water, broths, and herbal teas. Fortified plant-based milks (like soy) can also provide nutrients, while smoothies can be an easy way to get calories and vitamins.