What Are the Causes of Mucus?

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Mucus is a liquid substance that can range in consistency from watery to thick and slimy in nature. It is created by the body as a defence mechanism to protect itself from illness and irritants. Mucus membranes create mucus and are found in the nose, eyes, throat and lungs. A relatively consistent amount of mucus is normal and is nothing to be worried about. However, unusually large amounts of mucus may occur as the result of an underlying illness or other condition. The cause of excessive mucus can be easy to pinpoint in most cases.


Increased mucus production is often caused by an underlying illness. If mucus is the most prevalent symptom, it is usually caused by something simple like allergies or the common cold. Other illnesses that result in excessive mucus production include pneumonia, flu and bronchitis.


Consumption of dairy products can cause mucus to thicken, making drainage more difficult. This result is exacerbated if one is mildly allergic to dairy products or if one eats it often.


Tobacco use irritates the mucus membranes in the nose and in the lungs, causing an increase in mucus production and the drying out of mucus in the nasal cavities. This results in hard, dry, mucus in the nose and thick hard-to-pass mucus in the sacs of the lungs. It often causes coughing in an attempt to expel the excess mucus. Eventually, this mucus can cause breathing difficulties and lead to illnesses like emphysema.

Inhaled irritants and allergens

Frequently inhaling dust, smog and other irritants in the air can result in swelling of the nasal passages and increased mucus production in an attempt to rid the body of irritating particles. This is what causes common allergy symptoms like sneezing and runny nose.

Hormonal causes

Pregnancy and taking birth control pills can also lead to increased mucus production. This is due to the change in hormones. Any changes in the body's natural balance can result in multiple symptoms such as mucus, nausea and dizziness until the body adjusts.

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