Why is my horse coughing?

According to UK equine vets, most coughs are caused by either allergic airway disease — equine asthma, triggered by dust and mould spores in hay and bedding — or by respiratory infection. Occasional coughs at the start of exercise can simply be the horse clearing mucus.

What is equine asthma?

Equine asthma (formerly called RAO or 'heaves') is a non-infectious, allergic inflammation of the lower airways, usually triggered by mould spores and dust in hay, straw and poorly ventilated stables. It causes coughing, nasal discharge and increased breathing effort, and cannot spread between horses.

Should I be worried if my horse coughs once or twice?

An occasional cough, especially at the start of exercise or while eating dusty hay, is usually nothing to worry about. A cough that persists for more than a few days, happens at rest, or comes with nasal discharge, fever or faster breathing needs veterinary attention.

How do I stop my horse coughing from dust?

Soak or steam hay, switch from straw to low-dust bedding such as shavings, maximise turnout, keep stable vents and windows open, avoid mucking out or sweeping while your horse is in, and feed from the floor so mucus can drain.

Can worms make a horse cough?

Yes — lungworm and migrating roundworm larvae can irritate the airways and cause coughing, which is one reason a vet-guided, testing-led worming programme matters. Your vet can advise on testing if a worm burden is suspected.

Horse Health

Horse Coughing in the UK

Published 18 July 2026Last updated 18 July 20264 min read

Quick answer

Most horse coughing in the UK comes from dust and mould spores in hay and bedding (equine asthma) or from infection. According to UK equine vets, soak or steam hay, use low-dust bedding and maximise turnout. Call the vet if the cough persists, or comes with fever, nasal discharge or faster breathing.

Key takeaways

Most **horse coughing** in the UK comes from **dust and mould spores in hay and bedding** (equine asthma) or from infection.
According to UK equine vets, **soak or steam hay**, use low-dust bedding and maximise turnout.
Call the vet if the cough persists, or comes with **fever, nasal discharge or faster breathing**.

Why horses cough

According to UK equine vets, horse coughs generally fall into two camps:

Allergic airway disease (equine asthma) — a non-infectious reaction to dust, mould spores and pollens; the most common cause of persistent coughing in UK horses
Infection — viral or bacterial respiratory disease, which can spread quickly through a yard

Less common causes include worms (lungworm or migrating larvae), choke, and heart or throat problems — which is why a persistent cough deserves a proper diagnosis rather than guesswork.

Common causes at a glance

Cause	Typical signs	First steps
Dusty hay or bedding	Cough when eating or first brought in; no fever	Soak or steam hay; change to low-dust bedding
Equine asthma	Recurring cough, worse when stabled; nasal discharge; heavier breathing	Improve air quality; vet assessment
Viral/bacterial infection	Cough plus fever, snotty nose, dullness; others on yard affected	Isolate, take temperature, call vet
Worms	Cough in poorly wormed horses, often youngsters	Vet-guided worm testing

Equine asthma — the dusty-hay cough

According to Peasebrook Equine Clinic, equine asthma (formerly recurrent airway obstruction or RAO) is an allergic response to mould spores typically found in hay and straw. Breathed-in spores cause inflammation, extra mucus and constriction of the lower airways.

Early signs may be mild — an occasional cough during exercise — but as the condition progresses, coughing becomes more frequent and happens at rest, with a raised respiratory rate and effort. Warning signs of respiratory distress include:

Breathing rate above 20 breaths per minute at rest
Flared nostrils and wheezing
Visible abdominal effort when breathing (a 'heave line' along the belly in long-term cases)

Equine asthma is not contagious, but it is a lifelong tendency — management focuses on the environment rather than a cure.

Coughs caused by infection

If your horse has a cough plus any of the following, suspect infection and call your vet:

Raised temperature (fever)
Thick or coloured nasal discharge
Dullness, reduced appetite
Other horses on the yard coughing

Isolate a coughing horse with a fever from the rest of the yard until your vet advises. Keeping up to date with your horse's vaccination schedule reduces the risk of equine flu spreading through a yard.

Cutting dust in the stable

According to Your Horse's veterinary advice, these five steps reduce coughing:

Use dust-free bedding — swap straw for shavings or another low-dust option, and soak or steam hay
Turn out as much as possible — air quality is far better in the field
Ventilate — keep vents and windows open at all times; avoid sealing barn doors
Don't muck out or sweep around your horse — stable them elsewhere while you work
Feed from the floor — a natural head-down position helps mucus drain from the airways

Remember that hay steamers kill mould spores rather than just wetting them, while soaking for around 30 minutes and draining well reduces respirable dust. Stabled horses are often worst in winter, when doors stay shut and hay feeding increases.

When to call the vet

Contact your vet promptly if:

The cough lasts more than a few days or keeps returning
Your horse coughs at rest, not just at the start of exercise
There is fever, nasal discharge, dullness or reduced appetite
Breathing rate or effort has increased
Exercise tolerance has dropped

Keep a note of when the cough happens — eating, exercise, stabled versus turned out — as this pattern genuinely helps your vet narrow down the cause.

Sources & further reading

Facts in this guide are rewritten in plain English from publicly available UK advice. We name the organisation where a specific point comes from their guidance. Links below go to the original pages — use them to read the source material directly.

PETHEALTH+ is independent. These organisations do not sponsor, approve, or partner with this website. Guidance checked against sources listed below (last updated 2026-07-18).

Frequently Asked Questions

Why is my horse coughing?: According to UK equine vets, most coughs are caused by either allergic airway disease — equine asthma, triggered by dust and mould spores in hay and bedding — or by respiratory infection. Occasional coughs at the start of exercise can simply be the horse clearing mucus.
What is equine asthma?: Equine asthma (formerly called RAO or 'heaves') is a non-infectious, allergic inflammation of the lower airways, usually triggered by mould spores and dust in hay, straw and poorly ventilated stables. It causes coughing, nasal discharge and increased breathing effort, and cannot spread between horses.
Should I be worried if my horse coughs once or twice?: An occasional cough, especially at the start of exercise or while eating dusty hay, is usually nothing to worry about. A cough that persists for more than a few days, happens at rest, or comes with nasal discharge, fever or faster breathing needs veterinary attention.
How do I stop my horse coughing from dust?: Soak or steam hay, switch from straw to low-dust bedding such as shavings, maximise turnout, keep stable vents and windows open, avoid mucking out or sweeping while your horse is in, and feed from the floor so mucus can drain.
Can worms make a horse cough?: Yes — lungworm and migrating roundworm larvae can irritate the airways and cause coughing, which is one reason a vet-guided, testing-led worming programme matters. Your vet can advise on testing if a worm burden is suspected.