What Do Wrinkles Above a Horse’s Eye Mean? Mood, Pain and Stress Explained

What Do Wrinkles Above a Horse’s Eye Mean? Mood, Pain and Stress Explained

By Dr Duncan Houston

Wrinkles above a horse’s eye are often called “worry wrinkles,” but counting the lines cannot tell you exactly how a horse feels.

Some horses naturally have several visible wrinkles while standing quietly. Others show few wrinkles even when alert, uncomfortable or painful. What may be more useful is a change in the angle and tension of the wrinkles within the same horse, interpreted alongside the eyes, ears, muzzle, posture, breathing and behaviour.

The eye is giving you a clue, not a signed emotional affidavit.

Quick Answer

Wrinkles above a horse’s eye are created partly by contraction of the muscles that raise the inner brow. Research suggests that the angle of the uppermost wrinkle may change during some short-term emotional situations, becoming narrower during grooming and wider during food competition.

However, the number and depth of wrinkles, eyelid shape and visible eye white did not consistently distinguish positive from negative situations. Eye wrinkles should therefore be treated as one small part of the horse’s complete expression, not as a standalone mood, stress or pain test. (PubMed)

Horse Eye Wrinkles at a Glance

What you notice	What it may mean
Familiar wrinkles that remain unchanged while the horse is relaxed	Normal individual facial anatomy
Wrinkles becoming wider or more pronounced during competition, handling or social conflict	Increased brow-muscle contraction or arousal
Wrinkle angle narrowing during gentle grooming	Possible relaxation in that particular context
More wrinkles without any other behavioural change	Not enough information to diagnose stress
Wrinkles with an angled eye, rigid expression and muzzle tension	Possible pain or discomfort
One eye squinting with tearing, cloudiness or swelling	Possible eye disease requiring prompt veterinary assessment
Wrinkles appearing while the horse is intensely watching something	Attention or vigilance rather than necessarily fear
Reduced facial tension after the trigger is removed	A short-lived response that is generally less concerning

The central principle is to compare the horse with their own normal expression rather than comparing one horse’s face with another.

What Are the Wrinkles Above a Horse’s Eye?

The lines usually seen above the upper eyelid can be influenced by the muscles that raise and contract the inner brow.

In the Equine Facial Action Coding System, raising the inner brow is described as a specific facial action. Contraction of this area can pull the upper eyelid and skin upwards and towards the inside of the eye, altering the shape, depth and angle of the visible wrinkles. (Frontiers)

However, not every visible line is an active emotional expression.

Some lines may be:

• Normal facial landmarks

• Permanently present skin folds

• Related to the shape of the skull and orbit

• Influenced by breed type

• More visible because of lighting, coat colour or camera angle

• Deepened temporarily when the brow muscles contract

This distinction matters. A horse may have three obvious wrinkles while resting comfortably because those lines are simply part of that horse’s normal face.

What Did the Original Horse Eye-Wrinkle Study Actually Find?

The original study was led by Dr Sara Hintze and involved 16 horses.

Each horse was exposed to four 60-second situations intended to represent different emotional experiences:

• Grooming

• Food anticipation

• Food competition

• A plastic bag being waved nearby

Each situation was preceded by a 60-second control period. Researchers then assessed photographs using six measurements:

1. Overall qualitative impression

2. Eyelid shape

3. Wrinkle depth or markedness

4. Visible eye white

5. Number of wrinkles

6. The angle between a line through the eye and the highest wrinkle

Only one measurement, the wrinkle angle, changed significantly.

The angle became:

• Narrower during grooming

• Wider during food competition

There was no significant change in wrinkle angle during food anticipation or exposure to the plastic bag. There were also no consistent effects on the number of wrinkles, wrinkle depth, eyelid shape, visible eye white or overall subjective impression. (PubMed)

What the Study Found

The angle of the uppermost wrinkle may respond to muscle relaxation or contraction during certain short-term situations.

What the Study Did Not Find

The study did not show that:

• Happy horses always have fewer wrinkles

• Worried horses always have more wrinkles

• Visible eye white means the horse feels positive

• A plastic bag always creates a predictable wrinkle pattern

• One photograph can reliably identify the horse’s emotional state

• Every horse responds to the same experience in the same way

The original results were promising, but deliberately cautious. The researchers concluded that further validation was required before eye wrinkles could be used as a reliable welfare indicator. (PubMed)

Does a Narrower Wrinkle Angle Mean the Horse Is Happy?

Not automatically.

The original authors interpreted the narrower angle during grooming as potentially reflecting relaxation of the muscles above the eye. The wider angle during food competition may have reflected stronger muscle contraction.

That interpretation is plausible, but it applies to changes within the same horse during specific controlled situations. It does not provide a universal angle that separates a happy horse from an anxious one. (Frontiers)

A narrow angle could also be influenced by:

• Normal facial conformation

• Breed type

• Head position

• Which wrinkle was measured

• The horse’s baseline facial anatomy

• Lighting and image quality

The most useful question is therefore not:

How wide is this horse’s wrinkle angle?

It is:

Has this horse’s expression changed from their normal relaxed baseline, and what else is happening at the same time?

Do More Wrinkles Mean More Stress?

No reliable evidence supports that simple rule.

In the original experiment, the number of wrinkles did not change consistently between the control and treatment conditions. Some horses already had visible wrinkles before any emotional stimulus was introduced. (PubMed)

A later study assessed 181 horses in apparently neutral situations. Researchers found substantial individual variation in wrinkle number, prominence and angle.

Age, sex and coat colour did not significantly explain that variation. Breed type affected the measured angle, with Thoroughbred-type horses having narrower average angles than Warmbloods and coldbloods. The authors cautioned that farm, management and housing differences may have contributed to this apparent breed effect. (Frontiers)

This means that comparing wrinkle counts between different horses is particularly unreliable.

One horse may look permanently concerned while actually waiting peacefully for dinner. Another may have a beautifully smooth forehead while planning a vigorous objection to the farrier.

Does It Matter Which Eye You Look At?

Current research has not found a consistent difference between wrinkle expression above the left and right eyes.

The study of 181 horses found no statistically significant side difference in:

• Overall wrinkle impression

• Number of wrinkles

• Wrinkle angle

The original emotional-context study also did not identify a meaningful side effect. (Frontiers)

This means either eye may be used when monitoring general wrinkle expression.

However, new asymmetry between the eyes remains clinically important. One-sided squinting, eyelid tension, tearing, swelling or avoidance of approach from one side may indicate ocular pain, impaired vision or another local problem rather than a general emotional state.

Can Eye Wrinkles Reveal a Horse’s Long-Term Mood?

This has not been proven.

A later study investigated whether eye wrinkles measured while horses were in a neutral situation correlated with their performance in a judgement-bias task. These tasks are designed to assess whether an animal responds to ambiguous situations in a more “optimistic” or “pessimistic” manner.

The number and angle of wrinkles did not correlate significantly with the optimism measure. Horses judged subjectively to look less worried tended to behave more optimistically, but the result did not reach conventional statistical significance and the sample was small. (Frontiers)

The researchers concluded that the study did not support using eye wrinkles as a validated measure of longer-lasting mood.

Eye wrinkles may therefore provide information about certain immediate expressions, but they cannot currently be used to diagnose that a horse is chronically anxious, depressed or unhappy.

Can Wrinkles Above the Eye Indicate Pain?

They can contribute to a pain assessment, but they should never be used alone.

Research describing the equine pain face has identified changes including:

• An angled appearance to the eye

• An intense or withdrawn stare

• Tension above the eye

• Low or asymmetrical ears

• Dilated nostrils

• Tension around the lips, chin and muzzle

• Prominent chewing muscles

These signs were observed when horses experienced experimentally induced pain and helped form the basis of facial pain-assessment tools such as the Horse Grimace Scale. (PubMed)

The important difference is that pain assessment uses a pattern of several facial and bodily changes, not the presence of one wrinkle.

A horse becomes more concerning when eye tension occurs with:

• Reduced appetite

• Repeated weight shifting

• Lameness

• Reluctance to move

• Pawing or flank-watching

• Abnormal posture

• Sweating

• Reduced interaction

• Guarding a body area

• A change in manure production

• Difficulty eating or chewing

Pain can also make a horse quieter rather than more expressive. A low wrinkle score does not prove that the horse is comfortable.

Why Facial Expressions Cannot Diagnose One Specific Emotion

A 2025 study compared facial activity during:

• A short nociceptive stimulus

• Social isolation

• Sedation

• Nociception combined with isolation

• Nociception combined with sedation

Researchers could distinguish some of the individual conditions using patterns of facial movement. However, pain occurring during social isolation could not be clearly separated from isolation alone. Pain combined with sedation appeared similar to the control condition. (Nature)

This demonstrates two important limitations.

First, a stressful management situation can produce enough facial activity to conceal or imitate pain-related facial changes.

Second, sedation may suppress the horse’s facial expression even when a painful stimulus is present. (Nature)

A recently sedated horse with a relaxed-looking forehead may still be painful. A socially isolated horse with pronounced wrinkles may be distressed, painful or both.

The whole clinical context matters.

What Does Visible Eye White Mean?

Visible sclera, commonly called eye white, is often interpreted as fear or distress. It may accompany arousal, but it is not specific enough to diagnose one emotion.

Importantly, the original wrinkle study did not find a significant difference in visible eye white between its positive and negative conditions. (PubMed)

In another grooming study, horses receiving grooming adapted to their individual preferences were more commonly observed with half-closed eyes and relaxed upper lips. Horses receiving a standardised grooming routine were more likely to show wide-open eyes or visible eye white, a high neck and contracted lips. (Nature)

Visible eye white can also be influenced by:

• Head and eye position

• Breed and individual anatomy

• The direction of attention

• Sudden movement

• Fear or excitement

• Pain

• Restraint

• Social conflict

It should be interpreted with the rest of the horse rather than labelled automatically as either fear or happiness.

What Does Blinking Tell You?

Blinking is another useful eye-area observation, but it is not a simple stress meter.

A 2024 study found that horses blinked less when selectively attending to something. The stronger the attentional demand, the greater the blink inhibition. Reward anticipation, by contrast, increased blinking. (PubMed)

A horse staring without blinking may therefore be intensely focused rather than necessarily frightened.

Reduced blinking becomes more concerning when combined with:

• Rigid posture

• Raised head and neck

• Fixed ears

• Rapid breathing

• Attempts to leave

• Inability to respond to familiar cues

• One-sided eye closure or discomfort

Repeated blinking or squinting affecting one eye may indicate irritation or ocular pain and should be distinguished from changes in normal spontaneous blink rate.

How Should You Read the Whole Horse?

A More Relaxed or Content Expression May Include

• Eyes partly closed without squinting

• Mobile or softly positioned ears

• A moderately positioned or lowered neck

• Relaxed lips and muzzle

• Normal breathing

• Normal weight distribution

• Willingness to eat, rest or interact

• No repeated avoidance of the situation

Gentle grooming associated with positive responses has been linked with half-closed eyes, a moderately positioned neck and relaxed or extended upper lips. (Nature)

An Alert or Uncertain Expression May Include

• Raised head

• Eyes opened more widely

• Reduced blinking

• Ears fixed towards the stimulus

• Tense neck

• Active nostrils

• Weight shifting in preparation to move

• Repeated orientation towards an object

Alertness is not automatically a welfare problem. The important question is whether the horse can assess the situation, respond normally and recover.

Possible Pain May Include

• An angled eye

• An intense or withdrawn stare

• Tension above the eye

• Low or asymmetrical ears

• Dilated nostrils

• Tense chewing muscles

• A tight muzzle or pronounced chin

• Altered posture or movement

• Reduced appetite or interest

These signs become more persuasive when several occur together and improve following appropriate pain treatment. (PubMed)

Possible Eye Disease May Include

• Squinting or holding one eye closed

• Excessive tearing

• Cloudiness or opacity

• Eyelid swelling

• Redness

• Discharge

• Rubbing the face

• An abnormal pupil

• Apparent difficulty seeing

• Sudden head-shyness

These signs should not be treated as an emotional-expression puzzle. They require a veterinary eye examination. (Cornell Vet College)

How Can Owners Monitor Eye Wrinkles Properly?

1. Establish Your Horse’s Normal Baseline

Take photographs when your horse is:

• Healthy

• Comfortable

• In a familiar environment

• Not eating

• Not immediately after exercise

• Not reacting to flies

• Not sedated

• Standing with the head in a normal position

Photograph both eyes from similar angles.

The purpose is not to calculate the perfect wrinkle score. It is to learn what the horse normally looks like.

2. Compare the Same Horse, Not Different Horses

Because individual anatomy and breed type can influence wrinkle appearance, a change within the same horse is more useful than comparing two unrelated horses. (Frontiers)

Ask:

• Are the wrinkles deeper today?

• Has the angle changed?

• Is the eye itself more angled or narrowed?

• Is one side different from the other?

• What else has changed?

3. Observe Before Approaching

Watch from a distance for one or two minutes.

A horse may change their expression as soon as a person approaches, particularly when the person predicts:

• Feeding

• Work

• Medication

• Veterinary examination

• Separation

• A painful procedure

Remote observation or stable-camera footage may provide a more accurate picture of the resting horse.

4. Record the Context

Write down what was happening when the expression appeared:

• Grooming

• Feeding

• Food competition

• Isolation

• Transport

• Riding

• Veterinary treatment

• Social conflict

• Exercise

• Rest

Without context, the same expression can be interpreted in several completely different ways.

5. Use Video as Well as Photographs

A still image can capture:

• A blink

• A momentary glance

• A brief muscle contraction

• An awkward head angle

• One instant that does not represent the wider interaction

A 30 to 60-second video shows whether the expression is sustained and how it relates to the horse’s movement, breathing and behaviour.

6. Look at Recovery

A brief facial change during a surprising event is less concerning when the horse:

• Returns to normal breathing

• Lowers the head

• Resumes eating

• Responds to the handler

• Stops staring

• Returns to their usual expression within minutes

Facial tension that persists for hours, appears repeatedly at rest or occurs without a clear trigger deserves closer investigation.

Eye-Wrinkle Risk Framework

Lower Risk

The horse has:

• Familiar, symmetrical wrinkles

• No recent change in expression

• Normal appetite and manure

• Normal movement

• Normal interaction

• No eye discharge or squinting

Action: Continue normal observation and use the expression as part of the horse’s baseline.

Moderate Concern

The horse develops:

• More pronounced wrinkles during a particular task

• A raised brow with mild body tension

• Increased vigilance

• Avoidance during grooming or handling

• An expression that resolves after the situation ends

• No other physical signs

Action: Reduce the intensity of the situation, observe recovery and review whether handling, equipment or social pressure is causing discomfort.

High Concern

The horse has:

• Persistent eye-area tension

• A change from their normal face at rest

• Reduced appetite

• Lameness or reluctance to move

• Repeated weight shifting

• Abnormal posture

• Colic behaviour

• Withdrawal or unexpected aggression

• Poor recovery after the trigger is removed

Action: Arrange prompt veterinary assessment. Do not assume the problem is purely emotional.

Critical

The horse has:

• One eye held closed

• Heavy tearing

• A cloudy, blue, white or yellow area in the eye

• Eyelid swelling

• Eye trauma

• Apparent sudden blindness

• An abnormal pupil

• Severe pain

• Collapse

• Neurological abnormalities

• Severe colic signs

Action: Contact a veterinarian immediately.

What Else Can Cause a Tense or Wrinkled Eye?

Eye wrinkles may be influenced by several overlapping factors.

Normal Facial Anatomy

Some horses naturally have prominent lines above the eyes, even when relaxed.

Breed Type

Research found differences in average wrinkle angle between broad breed categories, although management and farm-level confounding could not be completely excluded. (Frontiers)

Attention

A horse concentrating on a sound, horse or object may raise the brow and reduce blinking. (PubMed)

Short-Term Emotional Arousal

Food competition, separation, novel objects and handling can alter muscle tension around the eye.

Pain

Orthopaedic, abdominal, dental, ocular and other pain can contribute to an angled eye, intense stare and tension above the orbit. (PubMed)

Eye Disease

Corneal ulcers, uveitis, stromal abscesses, foreign material and eyelid disease may cause squinting and muscle contraction around one eye. Horse eyes can deteriorate rapidly after apparently minor trauma. (Cornell Vet College)

Sedation

Sedative drugs can suppress or alter facial-muscle activity, potentially making a painful horse look more neutral. (Nature)

Flies, Wind and Bright Light

Environmental irritation may temporarily alter blinking, eyelid position and muscle tension. Persistent or one-sided signs should not be blamed on the environment without examining the eye.

When Is This an Emergency?

Wrinkles alone are not an emergency.

Contact a veterinarian urgently when the eye-area change occurs with:

• Squinting or complete eyelid closure

• Excessive tearing

• A cloudy or blue cornea

• Redness

• Eyelid swelling

• Eye discharge

• A visible foreign object

• A cut to the eyelid

• Trauma from a branch, fence or another horse

• An abnormal pupil

• Apparent loss of vision

• Repeated rubbing of the face

• Severe head-shyness

• Rapid deterioration over several hours

Even a superficial corneal scratch can become infected and progress to severe inflammation, scarring or loss of vision. Acting quickly can substantially change the outcome. (Cornell Vet College)

Also seek urgent care if the tense expression occurs with:

• Repeated rolling

• Abdominal pain

• Collapse

• Severe lameness

• Incoordination

• Circling

• Seizures

• Abnormal awareness

In these situations, the facial expression is only one part of a broader medical emergency.

What Should You Do Right Now?

1. Stop the Current Activity

Stop riding, training, clipping or handling if the expression appeared suddenly during the task.

2. Observe the Entire Horse

Check:

• Appetite

• Water intake

• Manure

• Movement

• Weight-bearing

• Breathing

• Sweating

• Interaction

• Both eyes

3. Compare Both Eyes

Look for:

• One-sided squinting

• Unequal pupils

• Asymmetrical swelling

• Different tear production

• Cloudiness

• Redness

• Injury

4. Take Clear Photographs and Video

Use natural light where possible and capture:

• Both sides of the face

• The whole eye

• The wrinkles

• The horse’s posture

• Any abnormal movement

5. Prevent Rubbing

Keep the horse in a safe area without projecting nails, branches or sharp surfaces. A clean fly mask may help selected horses, but it should not delay examination and must not press against an injured eye.

6. Do Not Apply Leftover Eye Medication

Do not use another horse’s drops or an old prescription.

Topical corticosteroids are particularly dangerous when a corneal ulcer is present and should not be used until the cornea has been examined and stained appropriately. (MSD Veterinary Manual)

7. Contact Your Veterinarian

Describe:

• Which eye is affected

• Whether the horse is squinting

• Whether there is tearing or discharge

• Whether the eye is cloudy

• When the change began

• Any recent trauma

• Whether vision appears altered

• Any other pain or neurological signs

Common Eye-Wrinkle Interpretation Mistakes

Counting Wrinkles and Diagnosing Stress

The original study did not find that wrinkle number reliably changed with the emotional situations tested.

Treating Every Wrinkle as Newly Formed

Many visible lines are normal facial landmarks that become deeper or shallower as the muscles move.

Comparing Different Horses

Breed, conformation and individual anatomy can affect the expression.

Reading One Photograph as the Complete Story

A still image may capture a blink, glance or temporary reaction.

Assuming Visible Eye White Means Happiness

The original wrinkle study found no positive-versus-negative difference in visible sclera.

Assuming a Smooth Forehead Means the Horse Is Pain-Free

Pain may be expressed elsewhere in the face, posture and behaviour, and sedation can conceal facial signs.

Ignoring One-Sided Changes

General emotional expressions are usually assessed across the whole face. New unilateral squinting or tearing raises much more concern for local ocular disease.

Delaying an Eye Examination

Horse eyes can deteriorate rapidly. Cloudiness, tearing, swelling or squinting should not be monitored for several days to see whether the wrinkle angle improves.

How Can You Improve Everyday Welfare Monitoring?

Keep Baseline Photographs

Photograph the horse’s resting face every few months or when management changes.

Perform a Daily Eye Check

Look briefly for:

• Symmetry

• Tearing

• Discharge

• Cloudiness

• Swelling

• Squinting

• Injury

Record Behavioural Context

Note when tension appears and whether it is linked to:

• Feeding

• Tack

• Grooming

• Exercise

• Social interactions

• Separation

• Veterinary care

Monitor Trends

A repeated pattern is more informative than one observation.

For example:

• Wrinkles deepen every time the girth is tightened.

• One eye narrows only when ridden towards bright light.

• Facial tension appears before recurrent mild colic.

• The horse looks tense whenever one particular grooming area is touched.

These patterns can guide veterinary and behavioural investigation.

Use the Whole Horse

Combine the face with:

• Gait

• Posture

• Appetite

• Manure

• Heart and respiratory rate where appropriate

• Interaction

• Performance

• Response to touch

No single facial feature should overrule obvious physical evidence.

Frequently Asked Questions

Do more wrinkles above a horse’s eye mean the horse is stressed?

Not necessarily. Horses vary naturally in wrinkle number, and the original emotional-context study found no consistent change in wrinkle count. A change in angle or tension within the same horse may be more useful.

Can a relaxed horse have eye wrinkles?

Yes. Some horses have visible wrinkles during neutral or relaxed situations because of normal facial anatomy.

Which eye should I assess?

Research has not found a meaningful general difference between the left and right eye. New one-sided tension, squinting or tearing is still clinically important because it may indicate local pain or disease.

Are eye wrinkles a sign of pain?

They may form part of a pain-related facial pattern, particularly when accompanied by an angled eye, tense muzzle, altered ears, nostril dilation and physical signs of discomfort. Wrinkles alone cannot confirm pain.

Why have my horse’s eye wrinkles suddenly become more pronounced?

Possible explanations include attention, social stress, discomfort, pain, an eye problem or a management trigger. A persistent change at rest or a change accompanied by squinting, tearing, cloudiness, appetite loss or lameness warrants veterinary assessment.

Final Thoughts

Wrinkles above a horse’s eye may offer useful information, but the science does not support treating them as a simple emotional code.

The strongest original finding involved wrinkle angle, not wrinkle number. The angle narrowed during grooming and widened during food competition, while food anticipation, plastic-bag exposure, eye white, wrinkle depth and overall wrinkle count produced no consistent distinction.

Later research has added important caution:

• Breed and individual anatomy influence the baseline appearance.

• Eye wrinkles have not been validated as a measure of long-term mood.

• Pain can create tension above the eye.

• Stress and social isolation can imitate or conceal pain-related expressions.

• Sedation may suppress facial signs despite ongoing discomfort.

• Attention can alter blinking and the appearance of the eye.

Use wrinkles as a prompt to look more closely, not as the final answer.

Compare the horse with their own normal face, consider the context and assess the whole body. If the change is accompanied by eye pain, lameness, colic signs, neurological abnormalities or persistent behavioural deterioration, investigate the horse rather than attempting to decode the wrinkle.

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ASK A VET™ can help you organise facial photographs, behaviour videos, trigger patterns and changes in appetite, movement or eye appearance. Squinting, tearing, eye cloudiness, trauma or sudden visual change still requires prompt hands-on veterinary examination.