How to Help a Horse With Seasonal Allergies

By Dr Duncan Houston

A horse that coughs during exercise, breaks out in hives or rubs its mane and tail raw may appear to have one broad problem called “seasonal allergies”.

In reality, these signs can represent several very different conditions. A horse coughing because of dusty hay needs a different plan from one reacting to biting midges. A horse with sudden hives after medication needs a different response again.

The first question is not simply what your horse might be allergic to. It is whether the lungs, skin or whole body are involved, and whether this is a manageable seasonal flare or a genuine emergency.

Quick Answer

The most common seasonal allergy-related problems in horses are equine asthma, insect bite hypersensitivity and urticaria, commonly called hives.

Environmental control is the foundation of treatment. Reduce respirable dust for horses with asthma and prevent insect bites in horses with sweet itch. Seek immediate veterinary care if your horse has difficulty breathing at rest, pale gums, a weak pulse, rapid facial or tongue swelling, collapse or seizures. (Merck Veterinary Manual)

Horse Allergies at a Glance

Pattern	Common possibilities	What matters most
Coughing during exercise	Mild to moderate equine asthma, infection, upper airway disease or pulmonary bleeding	Whether there is fever, poor performance or abnormal breathing at rest
Coughing with abdominal breathing effort at rest	Severe equine asthma or another serious respiratory disorder	This requires urgent veterinary assessment
Mane and tail rubbing	Insect bite hypersensitivity, pinworms, mites or skin infection	Seasonality and whether the horse is damaging its skin
Belly, chest or ear itching	Culicoides, black fly or other insect hypersensitivity	The distribution often reflects where the insects prefer to bite
Sudden raised wheals	Urticaria caused by insects, medication, vaccines, feed, environmental exposure or an unknown trigger	Whether facial swelling, breathing difficulty or weakness develops
Persistent crusting or hair loss	Parasites, ringworm, bacterial disease, allergy, photosensitisation or tumours	Allergy should not be assumed before other causes are excluded
Year-round recurrent itching	Environmental allergy, parasites, pain or less commonly food-related disease	A structured dermatological investigation is needed

These patterns guide the investigation but do not confirm a diagnosis by themselves. (Merck Veterinary Manual)

Are All Horse Allergies the Same?

No.

Some allergic conditions are strongly associated with immunoglobulin E, or IgE. Insect bite hypersensitivity is an important example, where the horse reacts to proteins in the saliva of biting insects.

Equine asthma is more complicated. It involves airway inflammation, airway hyperresponsiveness, mucus accumulation and, in severe or longstanding cases, permanent remodelling and narrowing of the lower airways.

Hives are also not always caused by a classic allergy. Pressure, heat, exercise, sunlight and stress may produce similar swellings without one identifiable environmental allergen. (Merck Veterinary Manual)

This is why one antihistamine, supplement or feed change cannot reasonably be expected to fix every horse described as “allergic”.

What Are the Main Seasonal Allergy Problems in Horses?

Equine Asthma

Equine asthma is a chronic, non-infectious inflammatory disease of the lower airways.

It is broadly divided into:

• Mild to moderate equine asthma

• Severe equine asthma

• Summer pasture-associated severe asthma

Mild to moderate asthma may cause coughing, excess airway mucus and reduced performance without visible breathing difficulty at rest. Severe asthma can cause nostril flaring, prolonged expiration, wheezing, abdominal effort and respiratory distress while the horse is standing quietly. (Merck Veterinary Manual)

What Triggers Equine Asthma?

Common triggers include fine airborne particles from:

• Dry hay

• Mould spores

• Dusty bedding

• Bacteria and endotoxins

• Indoor arenas

• Hay stored above stables

• Pollens

• Air pollutants

• Irritating gases

• Sweeping, blowing or mucking out around the horse

The most dangerous particles may be invisible. What matters is the air immediately around the horse’s nose while it is eating and resting, sometimes called the breathing zone. Hay is often the greatest source of respirable particles and endotoxin exposure. (Merck Veterinary Manual)

Most horses with severe asthma worsen when stabled and fed dry hay. Summer pasture-associated asthma is the awkward exception. Those horses may become worse on pasture during hot, humid months, potentially because of grass pollens or fungal spores. (Merck Veterinary Manual)

Insect Bite Hypersensitivity

Insect bite hypersensitivity is one of the best-characterised and most common allergic skin diseases in horses.

It is also called:

• Sweet itch

• Queensland itch

• Summer eczema

• Culicoides hypersensitivity

Culicoides biting midges are the most common trigger, although black flies and other blood-feeding insects may also contribute. The horse reacts to proteins in insect saliva rather than merely to the mechanical bite. (Open Access LMU)

What Does Sweet Itch Look Like?

Signs may include:

• Intense rubbing and scratching

• Broken mane hairs

• Tail rubbing

• Hair loss

• Crusts and scabs

• Thickened or folded skin

• Hives or small papules

• Open sores

• Secondary bacterial infection

• Restlessness

• Reduced concentration or performance

Commonly affected areas include the ears, face, mane, withers, back, tail head, chest, ventral abdomen and limbs. The exact distribution varies with the insects present and where they prefer to feed. (Open Access LMU)

Severely affected horses may rub against fencing, trees, doors and feeders until the skin bleeds. Once the skin is damaged, infection and continued trauma can keep the horse itchy even after the original insect exposure has decreased.

Hives or Urticaria

Hives are raised areas of swelling within the skin. They may look like small circular bumps, large flat-topped plaques or broad areas where several swellings have merged.

Common triggers include:

• Insect bites or stings

• Medication

• Vaccination

• Topical products

• Environmental allergens

• Feed or supplements

• Contact irritants

Other possible causes include pressure, heat, exercise, stress, sunlight, vasculitis, ringworm and autoimmune skin disease. In many recurrent cases, the exact cause remains unknown. (Merck Veterinary Manual)

Hives often appear within minutes or hours and may disappear just as quickly. They are commonly seen over the back, flanks, neck, eyelids and legs. Most uncomplicated episodes are not dangerous, but hives can occasionally be part of a more severe systemic allergic reaction. (Merck Veterinary Manual)

Environmental Allergic Dermatitis

Some horses develop recurring skin inflammation associated with environmental substances such as pollens, moulds, dust mites or storage mites.

Possible signs include:

• Seasonal or year-round itching

• Hair loss from rubbing

• Papules

• Crusting

• Hives

• Recurrent skin infection

• Flares in particular buildings, paddocks or climates

Environmental allergic dermatitis may occur alongside insect hypersensitivity or respiratory disease. One horse can therefore have more than one trigger at the same time. (Open Access LMU)

Food-Related Allergic Disease

Food can trigger urticaria in some horses, but true equine food allergy remains poorly understood.

The current veterinary consensus is that:

• Food reactions are not well defined in horses.

• Many suspected cases have never been confirmed through a proper elimination and re-challenge trial.

• Positive blood or skin tests do not prove that eating the ingredient causes disease.

• Serum food-allergy testing is unreliable.

• A controlled elimination diet followed by dietary challenge is the only currently reliable diagnostic method.

A horse that is itchy all year should not automatically be placed on a grass-hay-only diet without first assessing parasites, insect exposure, environmental allergy, infection and pain. Any elimination diet must remain nutritionally balanced. (Open Access LMU)

What Are the Signs of Seasonal Allergies in Horses?

Respiratory Signs

Watch for:

• Recurrent coughing

• Coughing at the beginning of exercise

• Coughing while eating hay

• Clear or mucoid nasal discharge

• Reduced stamina

• Slower recovery after work

• Wheezing

• Increased respiratory rate

• Nostril flaring

• Prolonged expiration

• Abdominal effort when breathing

• A visible heave line in advanced disease

A horse with mild asthma may look normal at rest and only underperform during strenuous exercise. Severe asthma causes visible breathing difficulty at rest. (Merck Veterinary Manual)

Skin Signs

Watch for:

• Raised wheals

• Mane and tail rubbing

• Broken hairs

• Bald areas

• Thickened skin

• Crusts or scabs

• Open wounds

• Papules

• Facial or eyelid swelling

• Persistent itching

• Recurrent seasonal lesions

• Odour, pus or discharge

Heat, pain, pus or a strong smell suggests secondary infection or another skin disease in addition to any underlying allergy.

Whole-Body Signs

A severe systemic allergic reaction may cause:

• Sudden diarrhoea

• Excessive drooling

• Very pale gums

• Cold limbs

• A rapid heart rate

• Weak peripheral pulses

• Severe breathing difficulty

• Tremors

• Collapse

• Seizures

• Reduced responsiveness

Facial swelling is not always present during equine anaphylaxis. Pale gums, cold limbs, a weak pulse and sudden systemic deterioration can be the more important warning signs. (Merck Veterinary Manual)

How Worried Should You Be?

Lower Risk

The horse has:

• A few isolated hives

• Mild seasonal itching

• An occasional cough

• Normal appetite

• Normal temperature

• Normal breathing at rest

• No facial swelling

• No open wounds

What it may mean: A mild local reaction or early seasonal flare is possible.

What to do: Remove obvious triggers, photograph the skin and monitor closely. Arrange veterinary advice if signs last longer than 12 to 24 hours, recur or worsen.

Moderate Risk

The horse has:

• Frequent coughing

• Mild exercise intolerance

• Widespread hives

• Repeated rubbing

• Developing hair loss

• Mild secondary skin infection

• Recurrent seasonal episodes

• Normal breathing at rest

What it may mean: Equine asthma, insect hypersensitivity, urticaria or another skin condition needs investigation.

What to do: Arrange a veterinary examination within the next few days. Begin reducing dust or insect exposure immediately.

High Risk

The horse has:

• Increased breathing effort at rest

• Persistent rapid breathing

• Marked wheezing

• Severe itching with self-trauma

• Rapidly increasing facial swelling

• Recurrent hives after medication or vaccination

• Coughing with fever

• Thick or foul nasal discharge

• Reduced appetite or marked depression

What it may mean: Severe asthma, pneumonia, contagious respiratory disease, an escalating allergic reaction or serious secondary infection may be present.

What to do: Seek same-day veterinary assessment. Isolate a coughing horse with fever or infectious-type nasal discharge.

Critical

The horse has:

• Severe respiratory distress

• Pale gums

• Cold limbs

• A weak pulse

• Sudden diarrhoea and drooling after an exposure

• Tongue or airway swelling

• Collapse

• Seizures

• Minimal responsiveness

What it may mean: Anaphylaxis or another life-threatening emergency is possible.

What to do: Contact an emergency equine veterinarian immediately. (Merck Veterinary Manual)

What Else Can Look Like an Allergy?

Respiratory Conditions to Rule Out

Possible condition	Important clues
Viral respiratory infection	Fever, several horses affected, recent travel or watery nasal discharge
Bacterial pneumonia	Fever, depression, foul discharge, abnormal lung sounds and reduced appetite
Strangles	Fever, swollen lymph nodes, difficulty swallowing and thick discharge
Exercise-induced pulmonary haemorrhage	Poor performance, coughing after intense exercise or blood at the nostrils
Recurrent laryngeal neuropathy	Abnormal respiratory noise during exercise
Dynamic upper-airway obstruction	Noise and poor performance mainly during strenuous work
Cardiac disease	Poor performance, abnormal rhythm, oedema or altered exercise recovery
Lungworm or other parasites	Relevant grazing history, donkey contact or eosinophilic airway inflammation
Pulmonary fibrosis or interstitial disease	Progressive exercise intolerance and abnormal imaging

Equine asthma is not normally associated with fever unless another process, such as infection, is also present. A coughing horse with fever should not simply be treated as allergic. (Merck Veterinary Manual)

Skin Conditions to Rule Out

Possible condition	Important clues
Lice or mites	Visible parasites, scaling, winter occurrence or affected in-contact horses
Pinworms	Tail rubbing with irritation or eggs around the anus
Ringworm	Circular hair loss and scaling, with contagious potential
Dermatophilosis	Paintbrush-like crusts, often after wet weather
Bacterial folliculitis	Raised hairs, crusting and inflamed follicles
Onchocerciasis	Itching and lesions overlapping with insect hypersensitivity
Habronemiasis	Granular summer sores around wounds or eyes
Photosensitisation	Painful, crusted lesions on white skin exposed to sunlight
Sarcoid or squamous cell carcinoma	Persistent, changing or ulcerated growth
Contact irritation	Lesions beneath tack, wraps, shampoos or topical products

The mistake I see most often is calling every itchy summer horse a sweet-itch case before checking for parasites, infection, ringworm or tumours.

When Is This an Emergency?

Call an equine veterinarian immediately when your horse develops:

• Difficulty breathing at rest

• Severe nostril flaring

• Pronounced abdominal breathing effort

• Sudden pale gums

• Weak peripheral pulses

• Cold limbs

• Rapid lip, tongue or facial swelling

• Sudden diarrhoea and drooling after an injection, medication or sting

• Collapse

• Seizures

• Inability to stand

• Severe coughing with fever and depression

• A rapidly worsening painful skin reaction

Anaphylaxis is an extreme emergency. Treatment may require epinephrine, airway support, intravenous fluids and additional medication. Waiting for the hives to disappear is not an adequate response when the horse is systemically unwell. (Merck Veterinary Manual)

What To Do Right Now

1. Stop Exercise

Do not continue riding a horse that is coughing repeatedly, wheezing or recovering abnormally.

Exercise increases oxygen demand and may worsen respiratory distress.

2. Check the Horse’s Temperature

A normal temperature does not prove allergy, but fever changes the urgency and differential diagnosis.

When fever accompanies coughing or nasal discharge:

• Separate the horse from others.

• Use dedicated buckets and equipment.

• Stop travel and competition.

• Contact your veterinarian.

3. Move Away From the Likely Trigger

Depending on the signs, this may mean:

• Moving away from dusty hay

• Removing the horse during stall cleaning

• Leaving an indoor arena

• Moving into a well-ventilated area

• Bringing a sweet-itch horse inside during peak midge activity

• Moving away from standing water

• Stopping a newly introduced topical product

• Preserving the packaging of a recent medication, vaccine, feed or supplement

Do not make numerous unrelated changes at once unless the horse is in immediate danger. For recurrent disease, a trigger log is more useful than changing the entire management system overnight.

4. Photograph Skin Lesions

Take clear photographs of:

• The full distribution

• Individual hives

• Mane and tail damage

• Open wounds

• Facial swelling

Include the date and a size reference. Hives may disappear before the veterinarian arrives.

5. Record Recent Exposures

Review the previous hours and days for:

• New feed

• New hay

• Supplements

• Medication

• Vaccination

• Deworming

• Shampoo

• Fly spray

• Laundry or rug products

• Heavy insect exposure

• Stable or paddock changes

• Recent travel

6. Prevent Further Skin Trauma

For an intensely itchy horse:

• Remove sharp or broken rubbing surfaces.

• Use a clean, correctly fitted fly sheet or mask where appropriate.

• Check beneath coverings daily.

• Keep open skin clean according to veterinary instructions.

• Avoid caustic creams and unverified remedies.

• Seek treatment for heat, swelling, discharge, odour or pain.

A poorly fitted or damp fly rug can trap sweat and worsen skin inflammation, so inspect the skin rather than treating the rug as a set-and-forget solution.

How Do Veterinarians Diagnose Horse Allergies?

Respiratory Investigation

The veterinarian may assess:

• Resting respiratory rate and effort

• Lung and tracheal sounds

• Nasal discharge

• Temperature

• Exercise history

• Hay, bedding and stable conditions

• Response to environmental changes

Additional testing may include:

• Upper-airway endoscopy

• Tracheal wash

• Bronchoalveolar lavage

• Thoracic ultrasound

• Radiographs

• Blood testing

• Dynamic exercise endoscopy

• Respiratory pathogen testing

Bronchoalveolar lavage cytology is central to identifying and characterising lower-airway inflammation. It can help distinguish mild to moderate asthma from severe asthma and identify the predominant inflammatory-cell pattern. (Merck Veterinary Manual)

A horse already in significant respiratory distress may need to be stabilised before elective diagnostic procedures are performed.

Dermatological Investigation

An itchy horse may require:

• Close inspection of the coat and skin

• Skin scrapings

• Hair examination

• Cytology

• Fungal testing

• Bacterial culture

• Parasite treatment trials

• Skin biopsy

• Evaluation for secondary infection

Insect bite hypersensitivity is primarily diagnosed from the history, lesion distribution, seasonality, exclusion of other itchy conditions and response to effective insect control. (Open Access LMU)

Are Allergy Tests Reliable?

Intradermal testing and serum allergen-specific IgE testing may help select allergens for immunotherapy once a credible clinical diagnosis has been established.

They should not be used as stand-alone screening tests because:

• Healthy horses may test positive.

• Affected horses may test negative.

• Sensitisation does not prove clinical disease.

• Test results may not match actual environmental exposure.

• Food-allergy blood testing is unreliable.

For suspected food-related disease, a veterinarian-supervised elimination and challenge trial remains the only reliable diagnostic approach. (Open Access LMU)

How Is Equine Asthma Managed?

Environmental Control Comes First

Environmental management is the single most important part of equine asthma treatment.

Medication may improve clinical signs, but coughing and airway obstruction commonly return when the horse remains exposed to the same respirable particles. (Merck Veterinary Manual)

Focus on the Breathing Zone

Start with what surrounds the horse’s nose while eating and resting.

Important changes may include:

• Removing dry round bales

• Avoiding hay storage above stables

• Removing the horse during sweeping or mucking out

• Avoiding leaf blowers near occupied stables

• Improving ventilation

• Using low-dust bedding

• Keeping indoor arenas watered appropriately

• Preventing horses from burying their heads in dusty forage

• Reducing mould, manure and aerosolised irritants

A stable that looks clean can still contain harmful respirable particles. Hay is often the greatest source. (AAEP)

Change the Forage

Depending on the individual horse, alternatives to dry hay may include:

• Pasture

• Haylage

• Complete pelleted feed

• Hay cubes

• Hay pellets

• Thoroughly soaked hay

• Properly high-temperature-steamed hay

For conventional stable-associated asthma, pasture and fresh grass may be beneficial. Horses with summer pasture-associated severe asthma may require the opposite approach, including low-dust housing and reduced pasture exposure during their trigger season. (Merck Veterinary Manual)

Is Steamed Hay Always Enough?

No.

High-temperature steaming reduces respirable particles, but the clinical response is inconsistent. A recent controlled study in horses with severe equine asthma found that steamed hay caused a mild deterioration in lung function and inflammation and did not prevent exacerbation compared with dry hay. This does not mean steaming is useless for every horse, but it should not be assumed to be sufficient treatment for severe asthma. (PubMed)

What matters is whether the horse’s coughing, respiratory effort, performance and airway inflammation actually improve. Some highly sensitive horses need hay replaced with haylage, cubes, pellets or a complete low-dust ration.

Medication

Veterinary treatment may include:

• Systemic corticosteroids

• Inhaled corticosteroids

• Bronchodilators

• Inhaled medication delivered through an equine-specific device

• Treatment for concurrent infection when one is genuinely identified

Corticosteroids reduce airway inflammation. Bronchodilators can provide rapid short-term relief from bronchoconstriction but should not be used alone because they do not control the underlying inflammation. (Merck Veterinary Manual)

Antihistamines, mucolytic drugs, NSAIDs and leukotriene-receptor antagonists have not demonstrated meaningful therapeutic benefit for equine asthma. (Merck Veterinary Manual)

How Is Sweet Itch Managed?

Prevent Bites Before Treating the Itch

Insect avoidance remains the most effective treatment.

Useful measures include:

• Stabling during peak Culicoides activity

• Using strong fans in stables

• Moving horses away from standing water

• Using fine insect screening

• Choosing exposed, breezy turnout rather than sheltered damp areas

• Using well-fitted fly rugs, masks and belly coverage

• Applying an effective equine-labelled repellent

• Reapplying repellents after rain or heavy sweating

• Starting prevention before the horse begins rubbing

Culicoides are weak fliers. Fans and fine mesh barriers can materially reduce exposure, while standing water and still, sheltered areas increase midge contact. (Open Access LMU)

Repellent effectiveness varies substantially. Some products provide only a few hours of practical protection, despite longer label expectations. Natural or essential-oil products should not automatically be assumed effective or harmless.

Treat Secondary Skin Disease

Once a horse has rubbed the skin open, itching can be maintained by:

• Bacterial infection

• Moisture beneath rugs

• Crusting

• Continued rubbing

• Inflammation around wounds

The veterinarian may prescribe topical or systemic treatment depending on the severity and whether infection is present.

Antibiotics treat bacterial infection. They do not treat the underlying allergy.

Anti-Inflammatory Medication

Corticosteroids may provide rapid relief in severe cases, but repeated or longer-term treatment requires careful consideration of:

• Previous laminitis

• Endocrine disease

• Body condition

• Concurrent infection

• Competition medication rules

Antihistamines are frequently used, but controlled evidence is limited and responses are variable. Sedation may occur, and many antihistamines are prohibited under competition rules. (Open Access LMU)

Can Desensitisation Help?

Evidence for traditional immunotherapy made from crude commercial Culicoides extracts has been inconsistent, and the 2023 consensus did not support it as a reliably effective treatment for insect bite hypersensitivity. (Open Access LMU)

A newer double-blinded, placebo-controlled study using recombinant Culicoides allergens reported encouraging improvement, particularly as treatment continued into a second season. The study was small, so this is promising rather than proof of a universal cure. (Frontiers)

Immunotherapy should be developed through an equine veterinarian or veterinary dermatologist after the clinical diagnosis has been established.

How Are Hives Managed?

Mild, Short-Lived Hives

When the horse is bright, comfortable and breathing normally:

• Remove any suspected trigger.

• Photograph the lesions.

• Review recent feeds, supplements, medication and topical products.

• Monitor breathing, pulse and facial swelling.

• Contact your veterinarian if the hives spread, persist or recur.

Many uncomplicated episodes disappear within several hours. Local treatment may not be needed. (Merck Veterinary Manual)

Persistent or Recurrent Hives

Further investigation may include:

• Medication and vaccine review

• Feed and supplement review

• Insect control

• Environmental assessment

• Skin biopsy for unusual lesions

• Evaluation for vasculitis or autoimmune disease

• A controlled dietary trial

• Allergy testing used in clinical context

Antihistamines may help some horses, but their value is inconsistent. Severe urticaria may require veterinary anti-inflammatory treatment. (Merck Veterinary Manual)

Hives With Systemic Signs

Hives accompanied by breathing difficulty, pale gums, cold limbs, weakness, diarrhoea, a weak pulse or collapse should be treated as possible anaphylaxis.

Do not wait for the skin swellings to become more dramatic before calling. (Merck Veterinary Manual)

Common Horse-Allergy Mistakes

Assuming Every Cough Is an Allergy

Fever, contagious exposure, foul nasal discharge or several coughing horses requires an infectious-disease investigation.

Treating Asthma With Medication While Ignoring Hay

Medication frequently fails when the horse continues inhaling the same hay dust every day.

Using a Bronchodilator Alone

Opening the airways temporarily does not treat the airway inflammation driving asthma.

Calling Every Itchy Horse a Sweet-Itch Case

Pinworms, mites, lice, ringworm, bacterial disease, photosensitisation and tumours can all cause rubbing or hair loss.

Trusting a Food-Allergy Blood Panel

Serum testing cannot currently diagnose food allergy reliably in horses.

Changing the Entire Diet at Once

This makes the trigger impossible to identify and may produce nutritional deficiencies.

Relying on One Application of Fly Spray

Rain, sweat and short practical duration can leave the horse unprotected for much of the day.

Leaving a Damp Fly Rug in Place

Trapped moisture and friction can worsen skin inflammation and infection.

Assuming Natural Repellents Are Automatically Better

Some plant-derived products provide poor protection, irritate the skin or have not been tested adequately against Culicoides.

Waiting for Severe Breathing Difficulty

Persistent coughing, worsening recovery or declining performance are earlier opportunities to diagnose and manage airway disease.

A Practical Seasonal Allergy Plan

Four to Six Weeks Before the Usual Season

1. Review previous clinical signs and photographs.

2. Decide whether the main problem has been respiratory, dermatological or both.

3. Service stable fans and improve ventilation.

4. Review hay and bedding sources.

5. Obtain properly fitted fly rugs and masks.

6. Address standing water and drainage.

7. Discuss preventive medication with your veterinarian.

8. Review competition medication rules.

9. Record baseline breathing, coughing, performance and skin condition.

10. Begin prescribed immunotherapy early enough to be useful.

Every Day During the Risk Period

Monitor:

• Number of coughs

• Breathing effort

• Exercise recovery

• Nasal discharge

• Hives

• Rubbing

• New wounds

• Repellent coverage

• Skin beneath rugs

• Feed and hay changes

• Weather

• Pollen and insect conditions

A simple diary often reveals whether the flare follows a new hay batch, humid evening, pasture exposure or missed insect-control step.

During a Flare

1. Stop exercise if coughing or breathing is abnormal.

2. Move the horse away from dust or insects.

3. Check temperature.

4. Photograph skin signs.

5. Review recent medication, vaccines, feed and topical products.

6. Protect damaged skin from further rubbing.

7. Contact your veterinarian when signs are significant, recurrent or worsening.

8. Seek emergency care for breathing difficulty, pale gums, collapse or airway swelling.

Can Seasonal Allergies Be Prevented?

Complete prevention is not always possible, but the frequency and severity of flares can often be reduced through:

• Low-dust forage and bedding

• Excellent ventilation

• Removing horses during stable cleaning

• Avoiding dry round bales for asthmatic horses

• Midge-specific insect prevention

• Fans and fine screening

• Reliable fly rugs and masks

• Management of standing water

• Early treatment of skin infection

• Careful introduction of feeds and supplements

• Recording previous medication reactions

• Starting management before clinical signs become severe

• Regular veterinary review of recurring disease

The prevention plan must match the individual horse. A horse with stable-associated asthma and one with summer pasture-associated asthma may require opposite turnout strategies.

Frequently Asked Questions

Can Horses Get Hay Fever?

Horses can react to pollens and environmental allergens, but their signs do not necessarily resemble human hay fever. They more commonly develop lower-airway inflammation, coughing, poor performance, hives or itchy skin. Infection and other respiratory diseases must still be excluded.

Is Soaking or Steaming Hay Enough for Equine Asthma?

Sometimes, but not always. Soaking and steaming may reduce respirable particles, yet highly sensitive horses may continue reacting and need haylage, cubes, pellets or a complete low-dust feed. Recent evidence suggests steamed hay alone may not prevent severe asthma exacerbations. (AAEP)

Can I Give My Horse an Antihistamine?

Antihistamines are used in some horses with hives or allergic skin disease, but their effects are variable and sedation may occur. They have not demonstrated therapeutic benefit for equine asthma. Medication and competition withdrawal requirements should be discussed with your veterinarian. (Open Access LMU)

Are Equine Allergy Tests Reliable?

They may help select allergens for immunotherapy once the diagnosis has been established, but they should not be used alone to diagnose disease. Healthy horses may test positive, affected horses may test negative and food-allergy blood testing is unreliable. (Open Access LMU)

Can Sweet Itch Be Cured?

There is no consistently reliable cure. Most horses require ongoing prevention of insect bites and treatment of seasonal inflammation. New recombinant-allergen immunotherapy is promising, but further evidence is needed before it can be considered universally effective. (Open Access LMU)

Final Thoughts

Seasonal allergy signs in horses are common, but the correct treatment depends on which body system is involved and what is actually driving the flare.

The most important points are:

1. Horse allergies are not one disease.

2. Coughing may indicate asthma, infection or another respiratory disorder.

3. Fever is not typical of uncomplicated equine asthma.

4. Environmental dust reduction is the cornerstone of asthma management.

5. Dry hay is a major source of respirable particles.

6. Pasture helps many asthmatic horses but may worsen summer pasture-associated asthma.

7. Sweet itch is best controlled by preventing insect bites.

8. Fans, screening, rugs and strategic stabling are often more important than supplements.

9. Hives may be allergic, physical or idiopathic.

10. Facial swelling is not required for anaphylaxis.

11. Food allergy remains poorly understood in horses.

12. Blood testing cannot reliably diagnose food allergy.

13. Allergy testing should support clinical reasoning, not replace it.

14. Secondary infection can significantly worsen itching.

15. Earlier environmental control usually produces a better result than waiting for severe disease.

The mistake that causes the most harm is treating the word “allergy” rather than treating the horse in front of you. The distribution of the skin lesions, breathing pattern, temperature, season and response to environmental changes are what reveal which problem you are actually managing.

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ASK A VET™ can help you organise coughing patterns, skin photographs, hay and bedding changes, insect exposure and medication history while you work directly with your attending equine veterinarian. A horse with breathing difficulty at rest, rapidly developing swelling, pale gums, collapse or seizures still requires immediate hands-on emergency care.