Q: Why would my tongue be very itchy, especially at night? I have tried lots of remedies, including anti-fungal drugs, but to no avail.

A: It is often very hard to know why someone's tongue is itchy. It is possible that something is irritating the tongue and causing itching. Sometimes foods can cause irritation. Other things you put in your mouth, like toothpaste, could also be playing a role. Certain toothpastes, particularly whitening and tartar-control toothpastes, have chemicals in them that can irritate the mouth and tongue.

There is a syndrome known as the Burning Mouth Syndrome. This syndrome is associated with abnormal sensations in the mouth, usually described as burning of the tongue as well as itching and changes in taste. The cause and treatment are unknown.

Rarely, people have true food allergies, or hypersensitivity. Food allergies are caused by abnormal responses to a food triggered by the immune system. They are different from food intolerances, which do not involve the immune system. Food allergies can cause an itchy mouth or tongue. They also can cause severe allergic reactions including shock or cardiac arrest. A person with a food allergy may notice itching of the tongue and mouth when first starting to eat the food. Later, other symptoms, including vomiting, diarrhea, hives, asthma and weakness may develop. The most common foods that cause these reactions include shellfish, peanuts, tree nuts, fish and eggs.

There is another type of allergic reaction that can cause itching of the tongue, lips and mouth. It is called the Oral Allergy syndrome. This syndrome is most often seen in people with a history of hay fever. The symptoms are brought on when someone eats certain foods. Most commonly eating raw fruits or vegetables, especially celery, kiwi, peaches, apricots, apples and nuts, causes the allergy syndrome. People may also get a rash or blisters when exposed to the food. Eating the raw food may cause itchy tingly feelings in the mouth, lips and tongue. Just handling the food or juices can cause a reaction. Sometimes more severe symptoms occur including vomiting, diarrhea and trouble breathing. Interestingly, these reactions most often happen only when the food is raw. Cooking usually destroys the part of the food that causes the allergic reaction. So, for example, people who react to raw apples might be able to eat cooked apples or applesauce. Nuts are an exception — they can cause reactions whether cooked or raw.

If your tongue itching persists longer than a few days, you usually need to see a doctor or dental specialist for an evaluation. The clinician will need to inquire in detail about the foods you've eaten, the duration of symptoms, any allergic history, and your family history. This information might help the doctor to come up with an answer.