Foaming at the mouth is a physical symptom. It occurs when an excess of saliva mixes with air or gasses to create a foam.

Frothy saliva is a rare symptom; when you see it, you should be concerned and immediately contact a doctor or 911 for medical assistance.

1. Drug overdose

People use recreational drugs because they affect the brain chemistry, causing feelings like euphoria and cravings for more of the drug. Two of the most popular categories of drugs are opioids (painkillers) and stimulants, or “uppers.”

Common opioids are:

Common stimulants are:

If you take too much of one of these drugs, you could overdose, meaning your body can’t detox the drug before deadly symptoms take effect.

Common signs of opiate or stimulant overdose are:

Overdose causes foaming at the mouth because organs like the heart and lungs can’t function properly. Slowed heart or lung movements causes fluids to gather in the lungs, which can mix with carbon dioxide and come out of the mouth like a foam.

Drug overdoses can be fatal. The drug narcan is an antidote to opiate overdose. There is no treatment for stimulant overdose.

2. Seizure

When a person starts convulsing uncontrollably, they are having a seizure. A brain condition called epilepsy can cause seizures. There are also nonepileptic seizures, typically caused by trauma or psychological conditions.

Beyond convulsions, seizures can also cause:

Foamy saliva can occur during a seizure because the mouth is forced closed, which stimulates the salivary glands and makes you produce extra spit. When the mouth opens again, drool or frothy saliva can come out.

Foaming at the mouth can also occur following a provoked seizure. For example, one case study examined a police officer whose partner accidentally shot him in the head with a Taser while chasing a suspect. The second officer witnessed his colleague lose consciousness, fall to the ground, and begin foaming at the mouth.

Treatments for seizures include antiepileptic medication and brain surgery.

3. Rabies

Rabies is a viral disease that affects the central nervous system. Only warm-blooded animals can get rabies. Common carriers of the rabies virus are:

  • raccoons
  • foxes
  • skunks
  • bats
  • coyotes
  • wolves

Animals less commonly affected by rabies are:

  • cows
  • dogs
  • cats
  • ferrets
  • humans

The rabies virus is present in the saliva. If an affected animal bites you or licks an open wound or scratch you have, you may get it.

Rabies can only be diagnosed from a brain tissue sample, so it’s important to watch for symptoms of the virus. Foaming at the mouth is the most characteristic symptom of rabies. This happens because the virus affects the nervous system and the animal or person can’t swallow their saliva.

Other symptoms are:

There is no way to treat rabies. If you think you have been exposed to rabies, clean your wound with soap and water and put a muzzle on your pet. Then immediately visit an emergency room where you will be given a rabies vaccine.

The three causes of foaming at the mouth are very specific and require unique treatment methods:

  • Some drug overdoses can be treated with an injection of narcan.
  • Epileptic seizures can be treated with antiepileptic medication.
  • Nonepileptic seizures can be treated with medication or psychotherapy.
  • Rabies can be prevented with a rabies vaccine and a series of other injections.

Foaming at the mouth can be a sign of a serious medical condition. If you experience foaming at the mouth, or see someone with foamy saliva, call your doctor or 911 immediately.