Subcutaneous Emphysema in Horses: Swelling That Crackles Under the Skin

By Dr Duncan Houston

Subcutaneous emphysema is one of those conditions that can make a horse look like it is inflating under the skin.

The swelling often feels soft, puffy, and strange. When you press it, you may feel a crackling sensation, almost like bubble wrap beneath the coat. That crackling is caused by air trapped under the skin.

Sometimes this happens after a wound acts like a one-way valve, letting air into the tissues as the horse moves. In other cases, it can point to something much more serious, including chest trauma, pneumothorax, tracheal injury, lung injury, or a gas-producing infection.

The swelling itself is not always the most dangerous part. The real concern is why air is getting under the skin in the first place.

Quick Answer

Subcutaneous emphysema in horses means air is trapped under the skin, causing soft swelling that crackles when pressed. It is commonly associated with wounds around the axilla, which is the area between the forelimb and chest, but it can also occur with neck wounds, chest wounds, rib injury, tracheal injury, or serious infection. Any horse with new crackling swelling, a wound near the chest, breathing changes, fever, depression, or rapidly spreading swelling should be examined by a veterinarian promptly. (IVIS)

What Is Subcutaneous Emphysema?

Subcutaneous emphysema means air has entered the tissue layer beneath the skin.

In a horse, it may look like:

• Soft swelling under the skin

• Puffy skin that shifts or spreads

• Crackling when the area is pressed

• Swelling that expands over hours or days

• Skin that looks raised but not necessarily painful

• Air tracking away from a wound site

The word “emphysema” here does not mean the same thing as chronic lung emphysema in people. It simply means air is present in tissue where it should not be.

The most important clinical clue is crepitus, which is the crackling sensation felt when air bubbles are present under the skin. Horse Side Vet Guide describes this as a soft, puffy, air-filled swelling that often occurs as a complication of upper limb, axillary, or groin wounds, although tracheal wounds, lung wounds, and gas-producing infections can look similar and may be life-threatening. (Horse Vet Guide)

Why Does Air Get Under a Horse’s Skin?

The classic mechanism is a wound that behaves like a one-way valve.

This often happens around the axilla, the soft area between the forelimb and the chest wall. As the horse walks, the movement of the limb can pull air into the wound. The tissue then closes or shifts in a way that traps the air inside. With repeated movement, more air is pumped under the skin.

IVIS guidance on axillary wounds notes that subcutaneous emphysema may not be present when the horse is first examined. It can develop later as air progressively accumulates in the subcutaneous tissue because the wound acts as a one-way valve. (IVIS)

This explains why an axillary wound may look minor at first, then become dramatic several days later.

Why Axillary Wounds Are So Important

The axilla is a high-motion area. Every step moves the forelimb against the chest wall. That movement can turn a small puncture or laceration into an air-pumping wound.

Axillary wounds can be deceptive because they may be hidden by the forelimb, difficult to bandage, and hard to inspect properly. A small skin opening may connect with a deeper tissue pocket. If that pocket draws in air, swelling can spread over the chest, shoulder, trunk, neck, or even much of the body.

A review of seven horses with axillary wounds found that all seven developed subcutaneous emphysema, five developed pneumomediastinum, and four developed pneumothorax. In the cases where timing could be assessed, subcutaneous emphysema developed on average about three days after the initial wound, with a range of two to four days. (Publishing Services)

That timing matters. A horse may look stable on day one but develop more concerning signs later.

Why This Can Become Dangerous

Subcutaneous air under the skin can look alarming, but the air itself may gradually reabsorb once the source is controlled. The bigger concern is where the air is coming from and where it may travel.

Possible complications include:

• Pneumomediastinum, which is air in the central chest space

• Pneumothorax, which is air in the pleural space around the lungs

• Tension pneumothorax, a rapidly progressive and dangerous form of pneumothorax

• Impaired breathing

• Infection tracking through tissue planes

• Wound contamination

• Hyperthermia if extensive trapped air insulates the body

• Gas-producing bacterial infection, including clostridial myonecrosis in rare severe cases

MSD Veterinary Manual notes that thoracic wounds can cause pneumothorax, hemothorax, or pneumomediastinum and may require advanced imaging or thoracic drainage. It also states that any horse with chest trauma and breathing difficulty should have open wounds sealed with airtight bandages and be evaluated for pneumothorax or pneumomediastinum. (MSD Veterinary Manual)

This is why the safest approach is not to watch it for days without advice.

What Does Subcutaneous Emphysema Feel Like?

Owners often describe it as:

• “Bubble wrap under the skin”

• “Rice Krispies under the coat”

• “A puffy swelling that crackles”

• “Air moving under the skin”

• “The horse looks inflated”

That crackling sensation is the key difference between air and ordinary fluid swelling.

Fluid swelling usually feels soft, warm, doughy, pitting, or tight. Air swelling feels light, puffy, and crackly. However, crackling should not be treated as automatically harmless because gas-producing bacterial infections can also produce gas in tissues. Horse Side Vet Guide specifically warns that bacterial infection with gas production, tracheal wounds, and penetrating lung wounds can appear similar and require immediate veterinary assessment. (Horse Vet Guide)

Severity Guide: How Worried Should You Be?

The key decision point is this: new crackling swelling with any wound near the chest, axilla, neck, or upper limb should not be ignored.

What Else Can Cause Crackling or Soft Swelling?

Subcutaneous emphysema is an important diagnosis, but it is not the only possibility.

Important rule-outs include:

Axillary wound

This is one of the classic causes. A wound between the forelimb and chest wall can pump air under the skin as the horse walks.

Chest wound

A penetrating thoracic wound can allow air into the chest or surrounding tissues. This is more serious because pneumothorax may develop.

Neck wound or tracheal injury

Air can escape from the airway and track into the tissues. Neck wounds with crackling swelling should be treated seriously.

Lung injury or rib fracture

Blunt or penetrating trauma can damage the lung or chest wall. Thoracic trauma can lead to pneumothorax, pneumomediastinum, hemothorax, rib injury, and respiratory distress.

Gas-producing bacterial infection

Some infections produce gas within tissues. This is much more dangerous than simple trapped air and may be associated with fever, pain, depression, swelling, heat, and rapid deterioration.

Cellulitis or abscess

These usually feel more fluid-filled, warm, painful, or firm rather than airy and crackly, but early signs can overlap.

Hematoma or seroma

Blood or serum collections can cause swelling after trauma, but they do not usually crackle unless air is also present.

The real veterinary task is to decide whether this is uncomplicated air tracking from a wound, or whether it signals chest involvement, airway damage, infection, or deeper trauma.

When Is This an Emergency?

Subcutaneous emphysema should be treated as urgent if any red flags are present.

Call a vet immediately if your horse has:

• Laboured breathing

• Rapid breathing that does not settle

• Nostrils flaring

• Distress, anxiety, weakness, or collapse

• Pale, grey, or blue gums

• Fever

• Depression or dullness

• Reduced appetite

• Severe pain

• A wound near the chest, axilla, neck, or groin

• A puncture wound

• Rapidly spreading swelling

• Wound discharge, pus, bad smell, or heat

• Swelling after trauma, a fall, kick, collision, fencing injury, or impalement

• Any suspicion that the chest has been penetrated

MSD Veterinary Manual states that penetrating chest wounds can lead to pneumothorax and respiratory distress, and because the mediastinum in horses is incomplete, a unilateral chest wound can lead to bilateral pneumothorax. (MSD Veterinary Manual)

That is the situation you do not want to miss.

What Should You Do Right Now?

1. Stop exercise immediately

Do not keep walking, lunging, riding, or turning the horse out.

Movement can pump more air into the tissues if the wound is acting as a one-way valve. Horse Side Vet Guide advises confining the horse to a stall and keeping movement to a minimum until the horse is evaluated. (Horse Vet Guide)

2. Move the horse carefully to a safe stable

If the horse is bright, breathing normally, and safe to move, place them in a clean, quiet stable.

If the horse is distressed, very lame, weak, or struggling to breathe, do not force unnecessary movement. Call your vet urgently and follow their instructions.

3. Look for the wound

Check carefully around:

• The axilla, between the forelimb and chest

• Shoulder

• Chest wall

• Neck

• Groin

• Upper limbs

• Belly

• Areas hidden by long hair, rugs, or tack

Small punctures matter. A tiny wound in the wrong place can create a large air pocket.

4. Do not puncture the swelling

Do not try to pop it, lance it, needle it, squeeze it, or drain it.

This is not one large bubble. It is air tracking through tissue planes. Puncturing it can introduce infection and does not fix the underlying one-way valve.

IVIS notes that subcutaneous catheters may sometimes be used to aspirate air in extensive cases, but this carries risks such as local infection and skin ischemia and should only be done when deemed necessary by a veterinarian. (IVIS)

5. Do not pack the wound yourself unless instructed

Packing an axillary wound can be an important treatment, but deep wound packing should be done by a vet or under direct veterinary instruction.

Incorrect packing can trap contamination, worsen infection, or fail to stop the valve effect.

6. Cover obvious wounds cleanly

If there is a visible wound and you can safely cover it, use a clean dressing to reduce contamination while you wait for your vet.

Do not fill the wound with powders, oils, caustic products, honey, disinfectants, or random creams before veterinary assessment.

7. Monitor breathing and temperature

Watch for:

• Increased breathing rate

• Laboured breathing

• Flared nostrils

• Sweating

• Dullness

• Fever

• Worsening swelling

• Reduced appetite

IVIS notes that the horse’s temperature should be monitored because extensive subcutaneous emphysema can have an insulation-like effect, with hyperthermia possible in warm climates or seasons. (IVIS)

How Vets Diagnose Subcutaneous Emphysema

A vet will usually start with the horse’s vital signs and a careful physical examination.

They may assess:

• Breathing rate and effort

• Heart rate

• Gum colour

• Temperature

• Lung sounds

• Extent of air under the skin

• Location and depth of wounds

• Whether the swelling is spreading

• Whether the horse is lame or painful

• Whether infection is present

Depending on the case, diagnostic tests may include:

• Wound exploration under sedation

• Ultrasound of the chest or wound region

• Radiographs to assess air tracking, pneumothorax, or pneumomediastinum

• Endoscopy if tracheal or airway injury is suspected

• Blood tests if infection or systemic illness is suspected

• Bacterial culture if discharge or infection is present

IVIS notes that pneumomediastinum is diagnosed based on radiographic findings, while radiographs or ultrasound can be used to confirm pneumothorax when progressive respiratory changes are suspected. (IVIS)

How Subcutaneous Emphysema Is Treated

Treatment depends on the cause.

The main aim is to stop more air entering the tissues, protect the wound, prevent infection, and monitor for chest complications.

Stall rest and movement restriction

Strict stall rest is often important, especially with axillary wounds. Movement of the forelimb can continue pumping air into the wound.

IVIS recommends strict stall rest for axillary wounds until the wound has healed, with additional movement restriction if the horse rolls or is very active in the stall. (IVIS)

Wound cleaning and packing

If the wound is acting as a one-way valve, your vet may clean and pack it with sterile gauze to stop air being drawn in. This is one of the most important treatments in many axillary wound cases.

The University of Minnesota large animal surgery notes summarise that resolution of subcutaneous emphysema in axillary wound cases was not achieved until treatment included packing the wound to stop it from acting as a one-way valve. (Publishing Services)

Bandage or seal

Some wounds need a bandage, seal, stent bandage, or body wrap depending on location.

For penetrating thoracic wounds, airtight sealing can be essential. MSD’s thoracic injury guidance describes covering penetrating thoracic wounds with plastic wrap and elastic tape to form an airtight seal to help prevent pneumothorax and pneumomediastinum. (MSD Veterinary Manual)

Antibiotics and pain relief

Your vet may prescribe broad-spectrum antibiotics, anti-inflammatory medication, and pain relief, especially if the wound is contaminated, deep, infected, or in a high-risk location.

MSD Veterinary Manual lists antimicrobials, bandaging, pain management, and tetanus prophylaxis as important parts of equine wound care when indicated. (MSD Veterinary Manual)

Tetanus protection

Any horse wound should trigger the question: is this horse protected against tetanus?

Your vet may recommend tetanus toxoid or antitoxin depending on vaccination status and wound risk.

Chest treatment if pneumothorax develops

If air enters the chest cavity and the horse develops respiratory distress, treatment may include thoracocentesis or thoracic drain placement.

The axillary wound case review summarised by the University of Minnesota notes that horses with pneumothorax and respiratory distress were treated with thoracocentesis or thoracic drains, while horses with pneumothorax but no respiratory distress were managed conservatively. (Publishing Services)

How Long Does It Take To Resolve?

Once the source of air entry is controlled, residual air under the skin often gradually reabsorbs.

The time frame depends on:

• How much air is present

• Whether the wound is still acting as a valve

• Whether the chest is involved

• Whether infection is present

• How well movement is restricted

• Whether the wound can be sealed or packed effectively

• How quickly the horse is diagnosed and treated

IVIS notes that once the source has been addressed, residual subcutaneous emphysema is usually self-limiting and rarely needs additional treatment. (IVIS)

The swelling may look dramatic before it starts to improve. What matters is that it stops spreading, the horse remains comfortable, breathing stays normal, and the wound is healing under veterinary supervision.

Can the Horse Recover?

Yes, many horses recover well when the underlying wound is controlled early and complications are avoided.

The prognosis is better when:

• The horse is bright and breathing normally

• The wound is identified early

• The valve effect is stopped

• Movement is restricted

• Infection is controlled

• Chest involvement is ruled out or treated promptly

• The horse is monitored for delayed complications

In the seven-horse axillary wound case series summarised by the University of Minnesota, all horses survived to discharge, including horses that developed pneumomediastinum and pneumothorax, but treatment included appropriate wound management and respiratory intervention when needed. (Publishing Services)

The cases that worry vets most are those with breathing changes, rapid progression, severe infection, chest trauma, or delayed recognition.

Common Mistakes Owners Make

Assuming the air swelling is harmless

It may be uncomplicated, but it can also be a sign of chest or airway involvement. The cause matters.

Continuing turnout or exercise

Movement can keep pumping air into the tissues, especially with axillary wounds.

Trying to pop or drain the swelling

This does not fix the source and can introduce infection.

Missing a small hidden wound

Axillary and groin wounds can be easy to miss. Always inspect areas hidden by the limb, coat, rugs, or tack.

Treating only the swelling

The swelling is a sign. The treatment target is the wound, airway, chest injury, or infection causing the air.

Waiting until the horse is struggling to breathe

Pneumothorax can develop after the initial wound. Serial monitoring matters because delayed respiratory complications have been reported with axillary wounds. (IVIS)

How To Prevent Subcutaneous Emphysema

Not every injury can be prevented, but you can reduce the risk of hidden wounds and delayed complications.

Helpful prevention steps include:

• Walk paddocks regularly for wire, broken posts, metal, nails, branches, and sharp debris

• Repair damaged fencing quickly

• Check gates, stable walls, partitions, feeders, and trailers for sharp edges

• Inspect the axilla after collisions, kicks, falls, or fencing injuries

• Check under rugs and tack after turnout or transport

• Treat small punctures seriously, especially near the chest, axilla, neck, groin, or upper limb

• Keep tetanus vaccination current

• Call your vet early for deep, hidden, or hard-to-bandage wounds

• Monitor wounds for several days, not just on day one

The practical message is simple: small wounds in high-motion areas deserve respect.

FAQs

Is subcutaneous emphysema in horses always dangerous?

No. Once the source of air entry is controlled, residual air under the skin may gradually reabsorb. However, it should still be assessed because it can be associated with axillary wounds, chest trauma, pneumothorax, tracheal injury, or gas-producing infection.

Why does my horse’s skin crackle when I touch it?

Crackling under the skin usually means air is trapped in the subcutaneous tissues. This can happen when a wound acts like a one-way valve and pumps air under the skin as the horse moves.

Should I pop the swelling?

No. Do not puncture, lance, squeeze, or drain the swelling yourself. The air is spread through tissue planes, not contained in one bubble. Puncturing it can introduce infection and does not fix the underlying cause.

How quickly can subcutaneous emphysema develop?

It may not be obvious immediately. In axillary wound cases, subcutaneous emphysema may develop over the following days as air accumulates. One case series found development typically occurred within two to four days after the wound. (Publishing Services)

When should I call a vet?

Call a vet promptly for any new crackling swelling, especially if there is a wound near the axilla, chest, neck, upper limb, or groin. Call urgently if there is breathing difficulty, rapid swelling, fever, dullness, pain, discharge, or suspected chest injury.

Final Thoughts

Subcutaneous emphysema can look dramatic, but the most important question is not how strange the swelling looks. It is why the air is there.

In many horses, the cause is a wound acting as a one-way valve, especially around the axilla. If the wound is controlled, movement is restricted, and infection is prevented, the trapped air may gradually resolve.

But this condition can also signal a more serious problem: pneumothorax, pneumomediastinum, airway injury, chest trauma, or gas-producing infection. That is why new crackling swelling should never be dismissed as just a weird lump.

If your horse looks like air is spreading under the skin, stop exercise, confine them safely, look for hidden wounds, avoid puncturing the swelling, and get veterinary advice early.

If you are unsure whether your horse’s swelling is harmless trapped air, a wound complication, or a sign of chest injury, ASK A VET™ can help you work through the signs and decide how urgently your horse needs veterinary care.