There are many possible causes of malformed, brittle, discolored or enlarged nails in dogs. These include trauma to the nail, infections of the nail, immune-mediated conditions that affect the nail, benign color changes and tumors of the nail bed. Cracked, bleeding, avulsed and painful nails represent the most common nail issue seen in dogs caused by loosening of the attachment of the nail. Swelling of a single digit with nail discoloration is most common with infection. Less commonly, swelling of a digit and changes to the nail can be secondary to cancers of the digit/nail bed. The most common cause of brittle and misshapen nails on many digits of multiple feet is an immune condition called symmetric lupoid onychodystrophy. Rusty color change to nails occurs most classically from a yeast infection and nails that turn partially white or black typically have benign underlying causes.
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Dog toenail injury
The most common nail issue seen in dogs is a broken nail. Often this involves one nail that snags on something and the pull partially pulls off the nail. The nail is often angled and bleeding at the nail base. Your dog will be painful and likely guarding that nail. If the nail wobbles easily, it can typically be removed by your veterinarian. Most of the time, in my experience with traumatic nail injuries, the nail is quite loose and a pair of hemostats can be used to grip the nail and quickly pull it off . Dogs are a lot more comfortable once the nail is removed. The nail will be hollow at the base and what’s left on the toe is the pink fleshy quick. The quick is the vascular tissue that protrudes from the bone of the digit and “feeds” the nail. The quick can be bleeding slightly but typically stops bleeding quickly.
Clipping the hair around the nail is helpful so the fur is not touching the sensitive quick. The foot can be soaked in an antiseptic solution like 2% chlorhexidine for 5-10 minutes. If the foot is very sore or bleeding slightly a bandage can be placed. However, it’s best to remove the bandage in 24 hours and start daily foot soaks for the next 5-7 days.
Avulsed nail with exposed quick below the nail.
Bacterial claw infections
Bacterial infections of the nail and nail bed are another common nail problem encountered in dogs. A bacterial infection develops most often secondary to trauma to the nail or nail bed. The toe may present as a solitary swollen toe and there may be discharge at the base of the nail or just a firm round swelling of the toe. Swelling of the base of the nail and inflammation or infection is called paronychia. Chronic claw infections often lead to erosion of the distal digital bone (P3). This is called osteomyelitis, and if this is present, amputation is recommended. Treatment of bacterial claw infections involves removing fractured portions of the nail, starting oral antibiotics, applying topical antibacterial agents and utilizing foot soaks. Antibiotics should be continued for 2 weeks past clinical resolution (typically for 4-6 weeks in total). Good empiric antibiotic choices include cephalexin and clindamycin.
Toe infection with swelling
Infection has eroded away the third phalanx (P3) of the swollen toe
Fungal nail disease in dogs
The most common type of fungal nail infection is with malassezia. Mallassezia commonly causes infection of the interdigital webbing of the paws in allergic dogs. It can cause mild inflammation of the nail beds with brown dry to moist debris/exudate along the nail bed. Oftentimes the nails show a classic rust colored change to the nail. This can be easily diagnosed in the exam room with a sampling of the debris along the nail bed looking for footprint shaped yeast under the microscope.
The picture below shows clear nail behind rust colored rings which represents healthy nail regrowth following a fungal infection of the claws. This is evident by clear healthy nails behind rings of rust colored nail. An active infection is treated with topical medicated wipes or medicated foot soaks. Ketoconazole is the most commonly selected antifungal medication. It is dosed at 5-10 mg/kg twice daily for 1-3 months beyond health claw regrowth.
Rust colored rings from previous yeast infection
Dermatophyotis is a less common form of fungal infection and is also known as ringworm. This type of infection can cause multi focal patches of hair loss, crusts and redness in other areas such as along the paw or on the face. Ringworm is zoonotic, meaning it can be spread to people as well. In people it often presents as a red raised ring on the skin and it is treated topically with a medicated antifungal cream like lamisil. Dermatophytosis can be diagnosed by submitting a fungal culture or fungal PCR of claw bed shavings or hair plucked around the claw bed or from affected skin nearby.
Dermatophytosis affecting the nail can cause enlargement of the nail and the nail may become darkened and brittle. A positive ringworm culture warrants environmental decontamination of the home with specialized cleaning. Cultures of other pets in the home (even if they are not showing any signs) is recommended because ringworm can be carried in some animals without any signs of disease.
Ringworm in dogs is treated with several months of oral antifungal medication like terbinafine and itraconazole.
Dermatophytosis of the nail enlarging the nail
Dermatophytosis affecting the nail and causing local infection of the skin
Dog nail problem: nails turning white or black
Leukonychia: Nails turning white
Leukonychia is a benign condition of the nails that is a form of vitiligo or pigment loss. It can cause part of the nails to turn white. The photos below show black nails turning white in areas.
The photo below shows leukonychia of the nails and vitiligo (pigment loss) on the fur too.
Nails with a black stripe: Nails turning black
The photo below shows a white nail with a black stripe. The black stripe is simply an aggregation of pigmented cells called melanocytes and represents another benign change.
Immune-mediated nail disease of dogs: Brittle, malformed nails
The most common nail disease that involves most of the nails on most of the paws is called: Symmetric Lupoid onychodystrophy (SLO). SLO primarily develops in dogs between the ages of 2-6 years, but can develop at any age.
These dogs are genetically predisposed to developing SLO:
- German shepherd
- Gordon setter
- English setter
- Finnish bearded collie
SLO is suspected to be an immune mediated condition. The trigger for development of the disease is unknown, but possible triggers have been suggested to be anything from reactions to vaccinations, food allergies and genetic predisposition.
When SLO initially develops, it may cause a dog to lose a claw. The claw that regrows will look abnormal and this will eventually happen to many claws on the dog.
SLO can cause limping, swollen digits, nail loss, bleeding, licking and secondary infection of the claws. Claw amputation and submission for histopathology is required for a definitive diagnosis. This is rarely performed as most veterinarians will make a diagnosis based on symptoms, history of the illness, exclusion of other causes, and response to treatment for SLO.
Treatment for symmetric lupoid onychodystrophy (SLO)
A combination therapy with tetracycline antibiotic and a B vitamin called niacinamide is given two to three times daily for three months. It can take 1-2 months to see improvement in the nails. After 3 to 6 months, if there is improvement in the new nail growth, the frequency can be reduced to once daily and then 4-6 months later the treatment can be discontinued. If recurrence develops, then the treatment should be re-instituted
Omega 3 fatty acid supplementation can also be tried at a dose of 50-60mg/kg/day of EPA and DHA (omega 3’s that are best suited for dogs) . Improvement would be expected within 3-4 months and a maximal response by 8 to 12 months. Essential fatty acids can be effective in some dogs as the sole therapy or as adjunctive therapy to tetracycline and niacinamide therapy. My favorite brand of fish oil for pets is Nordic Naturals. The bottle contains 4600mg/teaspoon of omega-3 fatty acids. However, the dose of total EPA and DHA per teaspoon (or per 5ml) is 875mg.
| Weight in pounds | Approximate Millilters of Nordic Naturals pet omega 4600mg/5ml |
| 10 lb | 1.5 ml |
| 20 lb | 2.5 ml |
| 40 lb | 5 ml |
| 60 lb | 7.5 ml |
| 80 lb | 10 ml |
Pentoxifylline is a drug used in other immune conditions and can be beneficial in 50-60% of cases. It is dosed at 15-25mg/kg twice a day for a 3 month trial. If the dog is experiencing normal regrowth of nails after 6- 9 months the medicine can be discontinued.
Keeping nails trimmed short to prevent contact with the ground provides good benefit .
Patients that are refractory to treatment with persistent pain and discomfort can have their third phalanx (the last bone on their digit) amputated as a last resort.
Digit tumors: tumors of the nail bed in dogs
Digital tumors account for 12% of all canine claw disease. 50% of digit tumors happen in older dogs (mean age of 9 years) and 75% are in large breed dogs.
Claw cancer occurs most frequently in the front limbs than hind limbs. Cancers are is diagnosed with a biopsy (piece of tissue surgically removed and submitted to a laboratory for identification).
Digit tumors are over-represented in the following breeds:
- Labrador retriever
- Standard poodle
- Rottweiler,
- Dachshund and
- Flat-coated retriever
The most common 2 types of digital tumors in dogs are:
- Squamous cell carcinoma (SCC)
- Melanoma
Squamous cell carcinoma of the nail bed in a dog
Squamous cell carcinoma of the nail bed has a 1 year survival of 95% and 75% after 2 years. SCC that arises from other parts of the digit are more aggressive and have a lower survival rate after 1 and 2 years: 60 and 40%. Dark, large breed dogs such as the Rottweiler, Black Labrador, Giant schnauzer and Standard poodle have an increased risk of SCC compared to other breeds.
Melanoma of the nail bed in a dog
Melanoma of the digit is more malignant than when it arises in other areas of body. The metastasis rate at the time of diagnosis is 38-58%.
The following breeds are over-represented:
- Scottish terrier
- Standard and Miniature schnauzer
- Irish setter
- Golden retriever
- Rottweiler
Digital melanoma in a dog
While digital squamous cell carcinoma is typically treated with surgery, nailbed (subungual) melanomas are more aggressive. Surgery is recommended with follow up treatment with the melanoma vaccine.
Conclusion
There are many possible causes of abnormal nails in dogs. It is always advisable to have your dog’s nail problem evaluated by your veterinarian to determine the cause and best treatment choice if needed!