It’s unlikely that any of your dogs will have a nail disease that isn’t related to trauma of some kind. So, if none of them ever pulls off a nail or cracks one by getting it stuck in a grate, you aren’t likely to need the expertise of a specialist like Klaus Loft, D.V.M., of Angell Animal Medical Center in Boston. A veterinary dermatologist, Loft says that more than 90 percent of canine nail issues are related to these kinds of trauma.

“It’s a very small number of all the dermatological diseases that we do see,” he says.

However, if your dog’s nails become crusty with irritated-looking tissue around the nail, you’re going to want someone like Klaus in your corner.

This dog has systemic lupoid onychodystrophy, a rare nail disease that typically affects every nail on all four paws. Photo courtesy of Angell Animal Medical Center.

Conditions like onychomycosis (pronounced uh-neek-oh-my-KOH’-sis) and systemic lupoid onychodystrophy (uh-neek-oh-DIS’-truh-fee) are hard to diagnose, require long-term treatment and often reoccur. “Onych” and “onycho” refer to the nail or claw – as the final structure on a dog’s toe is often referred to. Pretty much anything after it means “bad.”

SLO Is Uncommon

Systemic lupoid onychodystrophy, or SLO, is particularly troublesome, and fortunately quite rare.

“Most general practitioners would be uncomfortable to make a diagnosis of SLO unless they’ve seen or dealt with a case before,” Loft says. It typically shows up in middle-aged, larger dogs – 40 or more pounds – with no prior skin problems “whatsoever.” He says the nail looks like it’s “popping off, sort of like the hood of a VW bug popping up.” It usually affects all the nails on all four paws and is “often very acute.” All or most of the claws will typically be affected within three to four weeks.

“This is a relatively newly documented condition,” he says, first identified in the early ‘90s by Danny W. Scott, D.V.M, a Cornell University College of Veterinary professor and diplomate of the American College of Veterinary Dermatology. Loft has been seeing cases since 2001, but the 15 or so he sees each year make up less than 1 percent of his caseload.

Nails affected by disease. Removal or amputation is sometimes the only way to determine the disease’s cause. Photo courtesy of Angell Animal Medical Center.

There’s no chance your dog could have it without your attention being drawn to her paws. It’s very painful because the nails get loose. Whenever one touches the floor or ground, it shoots pain up the dog’s paw.

No cause has been pinpointed, Loft says. No breeds seem to have it more than others. No bacterial or viral infection in the nail has been identified as the cause. “Currently we speculate that SLO could be triggered by an infection or an immune response elsewhere in the body, such as a bladder infection that triggers an inflammatory response, but that has yet to be proven,” Loft says. And although there’s no scientific evidence that it’s related to a hyper-reactive or inappropriate immune response, it is suspected that might be the case.

“It happens without reason that we can identify thus far,” Loft says.

So, when it does happen, Loft often biopsies affected tissue to see if something else is going on, such as cancer, or an autoimmune disease or infection. Typically there’s a secondary infection associated with it, so he treats that and also provides pain management for the acute stage while the nails are falling off.

Once the nails have sloughed off, “they’re back on their feet,” Loft says.

But the condition isn’t cured.

A nail under treatment for systemic lupoid onychodystrophy. Photo courtesy of Angell Animal Medical Center.

He treats dogs diagnosed with SLO with combinations of doxycycline or tetracycline and niacinamide, plus supplementation with biotin (a B vitamin, also identified as “H”) and omega-3 and -6 fatty acids. While steroids or cyclosporine can be used as well, Loft doesn’t use them because he doesn’t believe the potential side effects will be justified – over the treatment period – for a dog whose life is not in jeopardy. The regimen of medication and supplements continues for two to three months, he says.

Unfortunately, about 50 percent of dogs he sees with the condition have a relapse within six months. Loft puts those dogs back on the regimen for six months – two to three times the length of the first round. If they have another relapse, they may need the medications for life, he says.

Because of this, Loft says, the whole experience can be as frustrating for the owner as the acute stage is painful for the dog.

More Common, but Zoonotic

Onychomycosis, on the other hand, has many known sources – several types of fungus, any one of which can enter the dog’s nail or adjacent skin when it’s had a previous trauma or a cut in the nail bed. It’s merely coincidental that a fungus spore manages to contaminate the wound. Once this happens, the nail’s keratin gets infected. “It’s very painful if you have a nail that’s infected all the way up to the nail bed,” Loft says. “When you’re close to the bone, you get a little more worried than if it’s on the back or the nose.” The good news is that fungus in the nail fold often spontaneously resolves itself, and usually only one or two nails on a single paw are involved.

For those that don’t resolve, treatment is, again, long-term; three to six months can be needed. The other bad news is that if it’s in the nails, it’s likely in the dog’s hair and also in your own skin as some of these fungal infections have an affinity for hair and skin, as well as nail tissue, and can be zoonotic.

A common fungus found in canine claws is often referred to as “ringworm,” but has nothing to do with worms of any kind, but rather, dermatophytes.

Loft prefers to pull the nail off or even have it amputated to determine what kind of fungus is causing the problem. The surgeon would decide how much to amputate, from part of a claw to as much as part of a toe to remove needed tissue for biopsy. Loft says the possibility of cancer should also be considered.

The type of fungus will determine the antifungal to be used. Over the course of treatment, the nail must be cultured regularly to see if there’s still evidence of infection.

The harder part is that any animal that’s been in contact with the dog must also be treated, and the dog’s entire home or the complete kennel must be decontaminated, Loft says. This includes getting rid of anything your dog sits on, wears or plays with if you can’t easily disinfect it; vacuuming and dusting thoroughly; cleaning draperies and washing curtains; and using a 1:10 dilution of bleach to wipe down all non-porous surfaces. Using replaceable filters on heating vents and a dehumidifier will also help prevent the fungus from surviving and spreading.

“Ringworm infections are a nuisance for everybody,” he says.

Less common fungal infections, from cryptosporidiosis to sporotrichosis, will also “gladly invade the nail area or anywhere else for that matter.” Some are much more dangerous than ringworm. Again, cultures determine the type of fungal organism.

A Simpler Case of Infection

Paronychia (pronounced pair-uh-NEEK’-ee-uh) is a term used to describe any infection that causes inflammation around the nail. Onychomycosis is a form of paronychia because it’s a fungal infection. But an infection in the nail fold can also be bacterial, from yeast or as a result of trauma. Most are a secondary infection related to some other condition, however.

This nail has a fungal infection, distinctly different from SLO. Photo courtesy of Angell Animal Medical Center.

Such infections can happen, for example, if your dog gets a cut in its nail bed, toe or paw on the beach, then licks or chews the paw, transferring bacteria from his mouth into the cut. Such transfer can also come from any surface your dog might walk on.

Many of these infections can be cleared up with antibiotics. However, it is important for the veterinarian to determine the cause so the right medicine can be prescribed. As with onychomycosis, only one or two nails are typically affected by such an infection.

Not to Worry

Some things you don’t need to worry about too much in regard to your dogs’ nails are allergies, nutritional diseases and parasitic infections.

“There’s very little symptom of allergy in nail disease itself,” Loft says. Allergies come into play with skin disease and sometimes paw disease. “Affected nails are indirectly innocent bystanders of allergies,” he says.

“Nutritional diseases are exceedingly rare today,” he says, because today’s dog food is balanced to give dogs all the nutrition they need. Nail problems due to poor nutrition were not that uncommon in the ‘70s and ‘80s, he says, when people were feeding homemade raw diets to their dogs and didn’t supplement properly.

The only nail problem in the U.S. associated with parasitic conditions that Loft is aware of is leishmaniasis, which is transmitted through a sand-fly bite. Loft says, though, that there’s not much of it here. When a dog does contract it, “one of the symptoms we can see dermatologically is that the nails develop an excessively absurd curvature.” It’s much more prevalent in Europe, he adds.

To prevent something minor from becoming serious or to catch something serious early on, watch your dogs’ nails for any swelling or redness in the tissue right around the nail, a change in nail color or tissue that doesn’t look normal in any way.

Because nail disease is rare, you’re more likely to seek out a specialist because of a mishap, and those are much harder to miss.