# Cat Throwing Up Phlegm: Causes and When to Worry

Cat throwing up phlegm usually means your cat brought up clear or frothy fluid from the stomach, not true mucus from the lungs. Most of the time it is stomach acid mixed with saliva, which is why it looks like foam or egg white. Real respiratory phlegm is possible, but it comes with coughing, not retching.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

## Quick Answer

- Clear, frothy, or stringy fluid after retching is almost always stomach contents, not lung mucus.
- Vomiting is an active, forceful process with salivation, swallowing, and belly contractions [1].
- A single episode in a bright, eating cat is often minor. Repeated episodes, lethargy, or appetite loss need a vet.
- True respiratory phlegm comes with coughing, wheezing, or trouble breathing, which is an emergency.
- Never give human anti-nausea or cold medicines to a cat. Your vet calculates any drug dose from your cat's weight and health.

## What Cat Throwing Up Phlegm Actually Looks Like

Owners use "phlegm" to describe several different things. The most common is a puddle of clear, bubbly fluid that looks like beaten egg whites. Sometimes it is stringy or slightly white. Sometimes it has a little yellow bile mixed in.

This material is usually a mix of swallowed saliva, stomach acid, and mucus that lines the stomach. It forms when a cat vomits on an empty stomach. The retching pushes up fluid and air, and the result is foam.

Vomiting in cats is the forceful ejection of stomach and upper small intestine contents through the mouth [1]. It is normally preceded by excessive salivation, repeated swallowing, retching, and forceful contractions of the abdominal muscles and the diaphragm [1]. That sequence is what separates vomiting from regurgitation.

Regurgitation is passive. It does not require effort or contraction of the abdominal muscles [1]. Regurgitated food and fluid tends to be undigested and may have a cylindrical shape reflecting the shape of the esophagus [1]. If your cat opens its mouth and food just falls out with no warning, that is regurgitation, and it points to a different set of problems.

### Stomach Mucus vs. Respiratory Phlegm

Here is the simplest way to tell them apart.

**Stomach mucus or foam:** Your cat retches, heaves, and contracts its belly. The fluid is clear, white, or yellow. It may contain hair, food, or bile.

**Respiratory phlegm:** Your cat coughs. The body posture is different, with the neck extended and the head low. The material is thicker and may be white, yellow, or green. Breathing may look labored.

If you are not sure which one you are seeing, film it on your phone. A short video is one of the most useful things you can bring to your vet visit.

## Main Causes of a Cat Throwing Up Phlegm

Many conditions can cause a cat to vomit clear or frothy material. Some are mild and pass on their own. Others need treatment.

| Cause | Typical clues | How urgent |
|---|---|---|
| Hairballs | Foamy fluid with a tube of hair, frequent grooming, long-haired breed | Routine if occasional. Frequent hairballs need a vet visit [1] |
| Empty stomach (bilious vomiting) | Happens early morning or after long gaps between meals, clear or yellow foam | Routine if otherwise well |
| Dietary upset | New food, table scraps, eating too fast, mild vomiting | Routine if it stops within a day |
| Gastrointestinal infection | Vomiting with diarrhea, possible cluster of sick cats in a home or shelter | Same-day visit |
| Feline asthma | Chronic cough, wheezing, fast breathing, mucus from the airways | Same-day to emergency, depending on breathing [2] |
| Foreign object or toxin | Sudden repeated vomiting, drooling, possible access to string, toys, plants, or medication | Emergency |
| Organ disease (kidney, liver, pancreatitis) | Weight loss, poor appetite, increased thirst, vomiting that keeps returning | Same-day visit |
| Parasites or heartworm disease | Vomiting with other signs, indoor or outdoor access | Routine to same-day visit |
| Tumor or esophageal problem | Chronic vomiting or regurgitation, trouble swallowing, weight loss | Same-day visit |

Vomiting can be caused by digestive system disease, kidney or liver failure, pancreatitis, or nervous system disorders [1]. Other causes include poisons, insect stings or snake bites, internal parasites including heartworm disease, infections, inflammation, drugs, ingestion of a foreign object, food allergy, and tumors [1].

### When the Problem Is in the Airways

Feline asthma is a common inflammatory airway disease. Clinical signs include chronic cough, wheezing, tachypnea, and respiratory distress [2]. Key features are bronchial hyperreactivity, mucus production, wall thickening, and airway remodeling [2].

That mucus production is the reason some owners describe a cat "coughing up phlegm." The material comes from the airways, not the stomach. Cats with asthma often stretch their neck out and crouch low when they cough. Some owners mistake this for a hairball. If your cat does this often, ask your vet about asthma testing.

### When the Problem Is in the Esophagus

Not every episode is vomiting. A recent report described a Siamese cat with a tortuous thoracic aorta that compressed the esophagus from the outside [3]. Imaging showed a vascular anomaly similar to a rare human syndrome called dysphagia aortica [3]. Endoscopy confirmed esophageal narrowing with ulcerative lesions caused by a hairball lodged at the narrow spot [3].

This is a rare case, but it shows why repeated "vomiting" that does not respond to standard care deserves imaging. If your cat regurgitates undigested food or has trouble swallowing, tell your vet.

### When the Cause Is Infectious

A virus called feline chaphamaparvovirus has been found in cats with sudden vomiting and diarrhea. In one study, it was identified in 30 of 136 samples (22%) from cats in shelters and a research colony [4]. It was found in vomit samples as well as feces [4].

This does not mean every vomiting cat has this virus. It does mean that when several cats in one home or shelter get sick at once, an infectious cause is possible. Keep sick cats separated and wash bowls and bedding often.

If your cat also has diarrhea, see [Cat Vomiting and Diarrhea: When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-vomiting-diarrhea-when-to-worry).

## Red Flags That Mean Emergency

Go to an emergency clinic now if you see any of these.

- Your cat is struggling to breathe, breathing with an open mouth, or has blue gums.
- Your cat is coughing up fluid and cannot stop.
- There is blood in the vomit, or the material looks like coffee grounds.
- Your cat may have eaten string, a toy, medication, a houseplant, or another toxin.
- Your cat is collapsed, weak, or unresponsive.
- Your cat is straining to vomit with nothing coming up, especially with a swollen belly.
- Your cat has had repeated vomiting for more than a few hours and cannot keep water down.

Call your vet the same day if you see these.

- Vomiting more than two or three times in a day.
- Vomiting that continues for more than 24 hours.
- Your cat is hiding, quiet, or not grooming.
- Your cat refuses food or water.
- Your cat has lost weight.
- Your cat has frequent hairballs. See your veterinarian if your cat is having frequent hairballs or vomiting repeatedly, because something more serious than a hairball could be to blame [1].

For a broader look at vomiting patterns, see [Cat Vomiting: When to Worry and What to Do](/knowledge/veterinary-medicine/online-vet-and-care-costs/cat-vomiting-when-to-worry-what-to-do).

## Safe Things You Can Do at Home While You Wait

Home care is about comfort and monitoring, not treatment. Do not give your cat any human medication.

**Withhold food briefly.** For an adult cat with a single mild episode, a short fast of a few hours is often fine. Do not fast a kitten, a senior cat, or a cat with a health condition without asking your vet first.

**Offer small amounts of water.** Ice chips or a shallow bowl of water can help. If your cat vomits right after drinking, stop and call your vet.

**Restart food in small meals.** Offer a bland, easily digestible diet in small portions several times a day. Your vet can tell you which food is right for your cat.

**Keep a log.** Write down the time of each episode, what the fluid looked like, whether food or hair was in it, and how your cat acted afterward.

**Separate your cat from other pets.** This helps you track who is eating, drinking, and using the litter box.

**Remove hazards.** Put away string, ribbons, rubber bands, small toys, and human medications.

**Do not use human anti-nausea drugs.** These are not dosed for cats and some are toxic. Your veterinarian calculates the dose from your pet's weight and health.

If your cat vomits mostly at night or early morning, see [Cat Vomiting at Night: Causes and When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-vomiting-at-night-causes-when-to-worry).

## What Your Veterinarian Will Check and Test

Your vet will start with a full history. Bring the video, the log, and a sample of the vomit if you can.

**Physical exam.** Your vet will check hydration, gum color, abdominal pain, breathing sounds, and body condition. They will also check for dehydration and weight loss.

**Basic bloodwork.** A complete blood count and chemistry panel look for infection, anemia, organ disease, and electrolyte problems.

**Fecal testing.** This checks for parasites and other causes of gastrointestinal upset.

**Imaging.** X-rays or ultrasound can find foreign objects, tumors, fluid, or organ changes. In the case of the Siamese cat, multimodal imaging was needed to find the vascular cause of the esophageal compression [3].

**Airway testing.** If asthma is suspected, your vet may recommend radiography, computed tomography, bronchoscopy, bronchoalveolar lavage, or allergy testing [2].

**Endoscopy.** A camera scope can look directly at the esophagus and stomach. This was used to confirm esophageal narrowing and ulcers in the reported case [3].

**Treatment.** Treatment depends on the cause. Some cats need fluids, anti-nausea medication, or a change in diet. Maropitant is one anti-nausea drug used in cats. In a review of controlled studies, maropitant reduced the risk of vomiting compared with control, with emesis in 11 of 141 treated cats versus 70 of 152 controls [5]. Your vet will decide if this or another drug is right for your cat.

If your cat is throwing up white foam or yellow liquid, see [Why Is My Cat Throwing Up White Foam And Yellow Liquid](/knowledge/veterinary-medicine/clinical-methods/why-is-my-cat-throwing-up-white-foam-and-yellow-liquid).

## Prevention and Monitoring

You cannot prevent every cause of vomiting, but you can lower the odds.

**Feed smaller, more frequent meals.** This helps cats who vomit on an empty stomach.

**Change food slowly.** Mix new food with old food over about a week.

**Control hairballs.** Brush your cat often, especially long-haired breeds. Talk to your vet about diet or supplements if hairballs are frequent.

**Keep hazardous items out of reach.** String, yarn, tinsel, rubber bands, and small toys are common culprits.

**Limit allergens if your cat has asthma.** Inhaled aeroallergens are part of the asthma picture [2]. Dust-free litter, air filters, and no smoking indoors can help.

**Stay current on parasite prevention.** Internal parasites are a known cause of vomiting [1].

**Watch for patterns.** Track when vomiting happens, what it looks like, and what your cat ate before. Patterns help your vet narrow the cause.

**Keep routine vet visits.** Early bloodwork can catch kidney, liver, and other problems before they become severe.

## Limitations and When to Contact a Veterinarian

This article covers common patterns, not your cat's specific case. Only a veterinarian who examines your cat can diagnose the cause.

**Contact an emergency clinic now** if your cat is struggling to breathe, has collapsed, is vomiting blood, may have eaten a toxin or foreign object, or is straining to vomit with nothing coming up.

**Contact your vet the same day** if vomiting happens more than a few times, lasts more than 24 hours, comes with diarrhea, or your cat is quiet, hiding, or not eating.

**Schedule a routine visit** if your cat has occasional hairballs, mild morning vomiting, or you want to review diet and prevention.

If you are unsure, call your vet and describe what you saw. A phone call costs nothing and can save time.

## Frequently Asked Questions

### Is clear mucus in cat vomit normal?

A single episode of clear or frothy fluid can be normal, especially on an empty stomach. Repeated episodes, or vomiting with lethargy or appetite loss, are not normal and need a vet visit. Vomiting is an active process with retching and belly contractions, so if you see that pattern often, get it checked [1].

### Can cats cough up phlegm from their lungs?

Yes, but it looks and sounds different from vomiting. Cats with airway disease such as asthma produce mucus in the airways and may cough it up [2]. The key sign is coughing, often with the neck stretched out and the head low, not retching and heaving.

### What if my cat is throwing up foam and not eating?

Foam plus refusal to eat is a warning sign. It can point to stomach upset, organ disease, a foreign object, or an infection. Do not wait more than a day. Call your vet, especially if your cat is also hiding or acting tired.

### Should I fast my cat if it keeps vomiting?

A short fast may help an otherwise healthy adult cat with one mild episode, but it is not right for kittens, seniors, or cats with other health problems. If vomiting continues, stop home care and call your vet. Cats can get sick quickly when they do not eat.

### How do I know if my cat has a hairball or something worse?

A hairball usually comes up as a tube of hair with some fluid. If your cat is having frequent hairballs or vomiting repeatedly, something more serious than a hairball could be to blame [1]. Weight loss, appetite changes, or vomiting between hairballs all point to a needed vet visit.

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## Related Articles

- [Cat Vomiting: When to Worry and What to Do](/knowledge/veterinary-medicine/online-vet-and-care-costs/cat-vomiting-when-to-worry-what-to-do)
- [Cat Vomiting: When to Worry and How to Help](/knowledge/veterinary-medicine/online-vet-and-care-costs/cat-vomiting-when-to-worry)
- [Cat Vomiting and Diarrhea: When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-vomiting-diarrhea-when-to-worry)
- [Cat Vomiting at Night: Causes and When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-vomiting-at-night-causes-when-to-worry)
- [Why Is My Cat Throwing Up White Foam And Yellow Liquid](/knowledge/veterinary-medicine/clinical-methods/why-is-my-cat-throwing-up-white-foam-and-yellow-liquid)
- [Cat Coughing: When Should You Worry?](/knowledge/veterinary-medicine/parasitic-diseases/cat-coughing-when-to-worry)
- [Cat Throwing Up Spit, Saliva, or Foam: Causes](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-throwing-up-spit-saliva)
- [Regurgitation in Cats: Causes and When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/regurgitation-in-cats)
- [Cat Threw Up: What to Do and When to Call the Vet](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-threw-up-what-to-do)

## References

1. [Vomiting in Cats - Cat Owners](https://www.merckvetmanual.com/cat-owners/digestive-disorders-of-cats/vomiting-in-cats). Merck Veterinary Manual.
2. [Feline Asthma-Update on Diagnosis and Treatment Recommendations](https://pubmed.ncbi.nlm.nih.gov/42320919/). The Veterinary clinics of North America. Small animal practice, 2026.
3. [A Presumed Dysphagia Aortica in a Siamese Cat](https://pubmed.ncbi.nlm.nih.gov/41787987/). Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2026.
4. [Feline chaphamaparvovirus (feline fechavirus) in different cat populations](https://pubmed.ncbi.nlm.nih.gov/41721216/). Journal of feline medicine and surgery, 2026.
5. [Receptor-Targeted Antiemetic Strategies in Cats: A Systematic Review and Intervention-Specific Meta-Analysis](https://pubmed.ncbi.nlm.nih.gov/42599757/). Veterinary medicine and science, 2026.

## Further Reading

- [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners)
- [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information)
- [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)