If your dog’s eyes seem consistently red you might be wondering what the cause could be, particularly if your dog is uncomfortable or showing any other signs of ill health. Redness usually means inflammation and irritation are occurring so you must get your dog’s eyes checked out by your vet, sooner rather than later.

Here is a list of some of the more common causes of red eyes in dogs –


Dogs with underlying allergies can suffer from red inflamed eyes, with an increase in itchiness and watering too. They can flare up to things like grass pollens, tree pollens, and house dust mites.

If your veterinary surgeon has ruled out other possible causes of disease, then allergies might be suspected. Treatments include lubricants to keep your dog’s eyes comfortable and antihistamines or anti-inflammatories to control the underlying allergic response. Some dogs may show other allergy symptoms too such as excessive sneezing and itchy skin. Let your vet know if you see other symptoms like sneezing or itchy skin.

Other conditions can cause your dog’s eyes to be excessively itchy too, such as physical irritations. This could be something in the environment like an increased amount of dust or sand blowing around for things like building works at home. 

Structural issues

There could be an abnormality with your dog’s eye, contributing to it becoming red and sore. Examples of this include:

  • Entropion – a condition whereby the skin of the eyelid is slightly rolled inwards, causing hair or eyelashes to rub against the cornea (surface of the eye). This condition is seen more commonly in some breeds than others. Dogs that have excessive skin folds and wrinkles, such as shar peis may be at higher risk. Surgery is usually required to correct this issue.
  • Distichiasis – a problem caused by small extra hairs growing on the inside of your dog’s eyelid. These rub against the cornea causing irritated and watery eyes. Treatment under high magnification is needed to remove and destroy the hair follicles and make your dog more comfortable.
  • Eyelid mass/tumour – a growth could start rubbing against the eye causing issues. This irritation could create redness and discomfort.
  • Cherry eye – a condition where a tear producing gland attached to the third eyelid (a protective membrane found in the corner of your dog’s eye) pops out. This protruding gland looks fleshy and pink initially but can become red and inflamed the longer it stays out. Surgery is usually required to replace and secure it again.


Both viral and bacterial conjunctivitis can cause similar symptoms. The eye usually becomes irritated and sore due to inflammation of the soft tissues in the eye, the conjunctiva. This may make your dog’s eyes appear red. An increased amount of discharge from the eye is usually noted, which is often green or yellow.

Your vet will examine your dog’s eye and check for other issues like ulcers on the cornea or any foreign bodies in the eye, like grass seeds or pieces of dirt. Treatment is often antibiotic eye drops, and possibly anti-inflammatory painkillers if your dog’s eyes are particularly sore.

Dry eye

Keratoconjunctivitis sicca (KCS) or ‘dry eye’ is an autoimmune condition that affects your dog’s ability to produce normal tears. With KCS the tear consistency becomes changed leading to a very mucoid and sticky discharge instead. Tears are important to keep the eye moist and well lubricated, and so when there is a problem the eyes become dry and more prone to infection and eye ulcers.

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A Schirmer Tear Test may be performed to test your dog’s tear production. Small paper strips are placed in the lower part of your dog’s eye to measure the number of tears he generates over a minute. If this amount is lower than normal then dry eye is suspected.

Dry eye is usually treated with a combination of eye drops including immunomodulatory drugs and lubricants, with regular checks needed to make sure things stay under control.


When there is an increase in pressure within the eye, your dog could develop a painful condition called glaucoma. This usually occurs when there is an imbalance between the amount of fluid produced and the amount that drains out. An increase in pressure can cause damage to delicate structures in the eye like the optic disc which can cause issues with vision. The eye itself can become swollen and red. This is an emergency and requires immediate veterinary attention. Medications can help reduce the pressure, surgery is also sometimes required.

If your dog has red eyes…

…it’s usually a sign that things aren’t right and he requires treatment to make him more comfortable. There are multiple reasons why your dog might have red eyes, so don’t delay or try and guess what the problem is yourself. Let your vet examine your pet and advise you on the best course of action to get things back on track.