Mucus coming into the mouth after eating is caused by postnasal drip, a sinus condition where mucus drips down the back of your throat because it isn’t able to drain properly out of your nostrils. Postnasal drip after eating can be caused by spices, extreme temperatures in your mouth or a food allergy. If you suspect that you’re allergic to a certain food, you should make an appointment with an allergist for a diagnosis.

Postnasal Drip

Postnasal drip commonly occurs because of increased mucus production in your sinus cavity. Your sinuses are lined with soft tissue and mucus membranes. If you eat a spicy food or go from eating an extremely cold food item to a hot food item, the mucus membranes in your sinuses will produce thin secretions down your throat, according to the American Academy of Otolaryngology. If you notice that you develop mucus in your mouth after you eat when you consume certain foods, you may have a food allergy.

Food Allergy Cause

Food allergies can cause postnasal drip within minutes of eating certain foods. Common food allergies are related to wheat, soy, eggs, peanuts, nuts, fish and dairy, according to the University of Maryland Medical Center. After you eat a food that you’re allergic to, your immune system attempts to fight it off by creating antibodies and other chemicals, such as histamine. The presence of histamine in the sinus tissue causes inflammation, swelling and increased congestion. This causes postnasal drip to form, leading to coughing and bad breath.


If your postnasal drip is due to environmental allergens, treat it by taking an antihistamine to reduce the amount of histamine in the soft tissue in the sinuses. This will help reduce irritation and mucus production. The American Academy of Otolaryngology states that a decongestant will help reduce inflammation in the sinuses, providing the excess mucus with the ability to drain through the nostrils properly. If you’re diagnosed with a food allergy, avoid consuming that food altogether.


If the mucus in your mouth after eating is related to a food allergy, you will experience other symptoms, such as asthma, hives, tingling in your mouth and digestive symptoms. A food allergy is a serious medial condition that needs to be under a doctor’s supervision. You should avoid all foods that you’re allergic to in order to prevent further complications.