Bodily Oddities

Gag reflex

Also called: Pharyngeal reflex · Laryngeal spasm

Touch the back of the tongue or the soft palate and the throat clamps shut. It keeps things out of the airway. Up to a third of healthy people barely have it, and that is normal.

Mouth and throat Nerves Reflex Reflex

How common

Present in about 2 of 3 people, weak or absent in 10–37% Very common · > 50% Absence in a healthy person is not a sign of disease.

Does this happen to you?

These are answers from visitors, not a study.

How it works

The gag reflex is a guard on the airway. Its sensors are in the back of the tongue, the soft palate, the tonsil area, and the back wall of the throat. Touch any of them and the throat squeezes shut, the soft palate lifts, and the tongue pushes forward. This throws an object away from the windpipe1.

Two cranial nerves run it. The glossopharyngeal nerve carries the touch signal to the brainstem2. The vagus nerve carries the order back to the throat muscles3. The loop is fast and does not involve thinking. Doctors test it to check that this part of the brainstem is working1.

The reflex is not the same as the swallowing reflex. Food that is chewed and moved back on purpose does not trigger it. Only an unexpected touch does.

How common it is

A surprising number of healthy people have a weak gag reflex or none at all. Studies put the figure between 10% and 37%1. In a 1995 study by Davies and colleagues, 37% of healthy adults did not gag when the back of the throat was touched1. This is a normal variation and it does not mean the airway is unprotected. Coughing and swallowing do most of the real work.

Other people have a very sensitive reflex. For them, dental work, throat swabs, and even brushing the back teeth are difficult. Anxiety makes it worse1.

History and culture

The reflex can be trained down. Sword swallowers spend months learning to keep their throat relaxed while a blade passes the exact points that trigger the gag4. Singers, divers who use snorkels, and people who wear dentures often report that their reflex faded over time. Some dentists teach patients to hum or to press a thumb into the palm during treatment. There is little evidence for these tricks, but distraction does seem to help1.

Sources and further material

  1. Encyclopedia Pharyngeal reflex Davies and colleagues, 1995, found the reflex absent in 37% of healthy adults.
  2. Encyclopedia Glossopharyngeal nerve The nerve that senses the touch.
  3. Encyclopedia Vagus nerve The nerve that drives the throat to contract.
  4. Encyclopedia Sword swallowing Performers who train the reflex away.
Mouth Trick

Khechari mudra

A hatha yoga practice in which the tongue is turned back and up behind the soft palate, into the space at the back of the nose. Very few people can do it without months or years of stretching.

Very rare without training
Mouth Involuntary

Tonsil stones

Small white or yellow lumps that form in the folds of the tonsils and sometimes come out when you cough. They smell bad and feel like something is stuck in the throat. They are harmless.

About 10% of people; up to 46% on CT scans Icky
Mouth Variation

Bifid uvula

The uvula, the dangling flap at the back of the throat, is split into two lobes, in about 1 to 2% of people. On its own it is harmless, but in a baby it can be a clue to a hidden cleft of the palate.

1–2% of people
Mouth Trick

Gleeking

Shooting a thin jet of saliva from under the tongue, sometimes a metre or more. About 35% of people do it by accident now and then. Only about 1% can do it reliably on command.

~1% on command Icky