SYMPTOM

Cracked or splitting claws

Owners notice a claw that is cracked, peeling in visible layers, bent at an odd angle, or has come away from the toe entirely, sometimes with bleeding or visible sensitivity when the paw is touched.

Traumatic Nail Injury

A claw snagged on carpet, fencing, or rough ground during normal activity is the most common cause of an acute crack, split, or avulsion, and typically affects a single claw on one paw without symmetry. This carries a straightforward mechanical explanation, and once the initial injury has settled the claw usually regrows normally over subsequent months. It is more likely in active or outdoor dogs and in cats that catch a claw while jumping or climbing.

Reduced Wear From Inactivity Or Joint Pain

Claws are naturally worn down through contact with hard ground during activity, and a pet that is less active because of joint pain or general ageing can develop overgrown, brittle claws that split more readily under everyday pressure. This pattern tends to affect multiple claws gradually rather than appearing as a single acute injury, and often coincides with a broader reduction in activity level.

Symmetric Lupoid Onychodystrophy

This immune-mediated condition of dogs causes claws to become dry, brittle, and to crack, split, or slough away from multiple paws in a roughly symmetrical pattern, typically starting with one or two claws before progressing to involve most or all of them over weeks to months. German Shepherds, Rottweilers, and Gordon Setters are among the breeds more commonly affected, with onset usually in young adult to middle-aged dogs, though it can begin at any age.

Infection Around The Nail Fold

Bacterial or fungal infection at the base of the claw can weaken the nail fold and lead to a claw that becomes misshapen, discoloured, or prone to splitting, often with visible swelling or discharge at the base. This is more likely to affect one or a small cluster of claws rather than being symmetrically distributed.

Subungual Tumour

A mass arising from the nail bed itself, including melanoma or squamous cell carcinoma, can cause a single claw to become deformed, loosen, or fracture repeatedly despite no clear trauma, and is more common in older dogs. Most cases involve a single toe, often with swelling of the toe or claw fold, though more than one digit can be affected. Squamous cell carcinoma made up about half of canine digit tumours in one multi-centre series of 64 dogs (52%) and melanoma 16%. Both are malignant, and squamous cell carcinoma commonly destroys the bone of the toe (20 of 25 cases showed bone loss on X-ray in a separate series). In older cats a digit tumour can be spread from a primary lung tumour and can affect several toes. From the outside these look the same as infection or injury.

Hypothyroidism

Reduced thyroid hormone in dogs can produce broader skin and coat changes, including claws that become dry, brittle, and prone to splitting, usually alongside other signs such as a dull coat, weight gain, or lethargy rather than as an isolated finding.

Why timing matters

Early observation

A single claw affected after an identifiable incident, such as catching it on furniture or fencing, most often reflects straightforward trauma in its early days and tends to improve steadily as the claw regrows.

Later presentation

Multiple claws becoming involved over subsequent weeks, particularly in a symmetrical pattern across different paws, shifts the picture towards an immune-mediated or systemic process rather than a series of coincidental injuries.

A single traumatic claw injury and an early immune-mediated process can look similar at first. Spread to other claws over days to weeks points towards an immune-mediated or systemic process. A problem that stays in one claw but does not heal, or recurs without injury, is the usual pattern of a nail bed tumour and is not a sign of a simple injury.

Conditions commonly associated

Symmetric Lupoid Onychodystrophy

This immune-mediated condition directly targets the claw-producing tissue, causing brittle, cracking, and sloughing claws across multiple paws in a symmetrical pattern.

Hypothyroidism in Dogs

Reduced thyroid hormone affects skin and claw tissue turnover broadly, producing claws that become dry, brittle, and prone to splitting alongside other coat changes.

Osteoarthritis in Dogs

Reduced activity from joint pain lessens the natural wearing-down of claws through ground contact, allowing them to become overgrown and more prone to splitting.

Pyoderma

Bacterial infection extending to the tissue around the nail fold can weaken claw attachment and lead to a claw becoming misshapen or prone to breaking.

Dermatophytosis (Ringworm)

Fungal infection can involve the claws themselves, producing a brittle, misshapen, or crumbling texture distinct from a traumatic split.

Squamous Cell Carcinoma

A tumour arising from the nail bed can cause a single claw to repeatedly loosen, deform, or fracture despite no clear traumatic cause.

Demodectic Mange

In demodectic mange, inflammation of the skin around the claw base (paronychia), often with secondary bacterial infection, can disrupt normal claw growth and produce thickened, overgrown or misshapen claws, which may then break. This is seen mainly in generalised or foot-centred cases.

When to explore further

Multiple claws affected in a roughly symmetrical pattern across more than one paw points towards a generalised process rather than a single traumatic event.

One claw that loosens, deforms or breaks without a clear injury, or a toe that is swollen at the claw base, cannot be told apart from a nail bed tumour by appearance at home. In one series of 117 dogs with digit masses, 61% of the masses were malignant, and 6 of the 19 dogs with digit melanoma (32%) already had spread to the lungs on chest X-rays at diagnosis. Diagnosis rests on veterinary examination, X-rays of the toe and a tissue sample. In a second series of 64 dogs, surgery improved survival and the authors advised early surgery whatever the tumour type.

Swelling, discharge, or an unpleasant odour at the base of a claw suggests an infective component distinct from a simple mechanical split.

Claw changes accompanying a broader pattern of coat dullness, weight change, or reduced energy point towards a systemic rather than purely local explanation.

A claw injury that continues to bleed, or one where the exposed quick stays raw and painful for more than a day or two, sits outside the pattern of a split that is settling on its own.

Photographing the affected claw or claws at intervals gives a useful record of whether the pattern is confined to one digit or spreading to others over time. Noting how many claws are affected, on how many paws, and whether the pattern is symmetrical helps distinguish a problem of one claw from a generalised one. Keeping track of any accompanying coat, weight, or energy changes adds context that a claw finding alone would not capture.

Last reviewed: 10 October 2026 · Dr Alastair Greenway MRCVS