Some people complain that milk makes their nose run, coats their throat and triggers coughing. Why is this so?
Everyone has mucus
Mucus is produced by cells within the nose, sinuses and lung. It consists of water, salt and various proteins that help trap germs and particles of dirt. Antibacterial enzymes and proteins called antibodies in mucus also help to kill germs and protect from infection. Mucus is moved towards the back of the throat by microscopic hair cells called "cilia", where it is then swallowed.
Mucus can irritate
Too much mucus can make the nose run or drip down the back of the throat, leading to post-nasal drip. Typically caused by infections or allergy, excessive mucus can trigger cough, sore throats and a husky voice.
Thick, dry mucus can also irritate the throat and be hard to clear. Dry mucus is more common in older people and in dry inland climates. Air conditioning, winter heating, dehydration and some medications (such as some antihistamines, antidepressants and blood pressure medicines) can aggravate the condition.
Milk and mucus
Some people complain that when they drink milk or other dairy products, their throat feels coated and mucus is thicker and harder to swallow. Recent research has shown that these feelings are due to the texture of the fluid and occur with similar liquids of the same thickness, and are not due to increased production of mucus. Symptoms of cow's milk allergy are very different.
Milk does not cause middle ear problems
Middle ear infections (otitis media) are very common in early childhood. Infections are even more common when children also have allergic rhinitis (hay fever). Allergic inflammation causes swelling in the nose and around the opening of the eustacian tube (ear canal)interfering with drainage of the middle ear. Like water in a stagnant pond, infection is more likely.
Children with cow's milk allergy sometimes appear to suffer from more frequent infections. This is not because milk causes infection, but rather because children with food allergy are more likely to suffer from other allergic disorders such as allergic rhinitis.
Eliminating dairy product does not help asthma or allergic rhinitis
Asthma and allergic rhinitis (hay fever) are normally triggered by substances that we inhale, such as pollen, dust mite, mould spores or animal danders. Dairy products rarely trigger asthma or allergic rhinitis. When they do, nasal symptoms are usually accompanied by obvious symptoms of allergy, such as severe hives, throat or tongue swelling or a drop in blood pressure.
Recent studies have shown that milk has no effect on lung capacity, and does not trigger symptoms in patients with asthma any more than placebo. When patients complain of cough after having cold milk, it is usually due to breathing in cool air as they drink, and usually disappears if they warm the milk first.
Cutting out important foods can adversely affect nutrition
Milk and other dairy products are an important source of calcium and other minerals needed for strong teeth and growing bones. Cutting out milk unnecessarily can limit choices, reduce enjoyment of food and may adversely affect nutrition. If it does become necessary to eliminate milk and other dairy products from your diet for some reason, make sure you substitute other calcium containing foods and drinks, or take a calcium supplement. If you need further information, consult a dietitian. In most sufferers, dietary restriction is of little benefit in asthma or allergic rhinitis, and distracts efforts away from more productive areas such as allergen avoidance.
© ASCIA 2010
The Australasian Society of Clinical Immunology and Allergy (ASCIA) is the peak professional body of Clinical Immunologists and Allergists in Australia and New Zealand.
Postal address: PO Box 450 Balgowlah NSW Australia 2093
This document has been developed and peer reviewed by ASCIA members and is based on expert opinion and the available published literature at the time of review. Information contained in this document is not intended to replace medical advice and any questions regarding a medical diagnosis or treatment should be directed to a medical practitioner. The development of this document is not funded by any commercial sources and is not influenced by commercial organisations.
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Content last updated January 2010