Humans are highly attuned to changes in their bodies: a daily peek in the mirror or a once-over from a partner will reveal any sudden moles or dark patches of skin. In a dog, changes can fly under the radar for weeks or even months, thanks in part to his coats covering his skin. Add in areas unlikely to be seen very often, such as the inside of the thighs and the stomach, and the “sudden” appearance of darker or black skin – a phenomena called hyperpigmentation – can feel alarming to a pet parent. Discerning the cause of hyperpigmented areas is crucial, as the underlying reason will be the deciding factor between taking (or forgoing) an emergency trip to the vet. So, what is hyperpigmentation in dogs? This article will explore what every dog owner needs to know in order to separate a dog’s harmless black splotches from worrisome spots.
What Causes Hyperpigmentation in Dogs?
Canine medical conditions such as Cushing’s Syndrome will cause significant dark discoloration, but will also have a raised, rough textural element. Additionally, raised spots with red or jagged edges can point to a canine skin infection, rather than a harmless skin color shift that can happen with age, injury healing, or genetics. In other words, not all hyperpigmentation is the same.
If a pet parent suspects that a skin-surface infection could be causing their dog’s hyperpigmentation, tests should be ordered at a local veterinary office, including examinations for mites and fleas. While these icky parasites don’t tend to gather in numbers large enough to mimic a splotch, they’re still bad news that could be causing allergic reactions in dogs when they bite.
Be prepared to answer questions such as:
- When was the last time your dog went outside?
- Is he currently being treated for fleas and ticks?
- Have you seen any evidence of adult fleas or flea dirt?
- Have you noticed any lack of appetite or thirst?
- Do the darker spots seem to be giving him any discomfort or itchiness?
These answers will help narrow down what could be a simple skin infection that can be cleared up with topical or ingested medicine from the vet. The vet can examine the site where the hyperpigmentation occurred and take skin scrapings or samples, if necessary, to examine under a microscope. Be patient, let the professionals examine the dog for telltale signs, and follow directions carefully if the vet prescribes specialty shampoo, topical remedies, or skin-soothing treatments. Also be sure to mention if any humans or other animals in the household have been experiencing skin conditions of their own, as this can help to rule out potential environmental contagion factors.
What is Hyperpigmentation in Dogs?
If the darker color is flush with the skin and he isn’t exhibiting any other health symptoms, this may simply be the canine equivalent of freckles or “beauty marks” in humans. These spots or blotches appear naturally in areas like his nose, paw pads, gums, and the rims of his eyes. In some breeds and specific pups, this coloring is more pronounced: some dogs have black spots on their tongue. The Shar-Pei, for example, has a purple-black tongue due to high natural concentrations of melanin, which causes darkening of the skin.
While a concerned pet parent might be worried something is “wrong” with their canine companion, in the vast majority of cases, this darkening is completely harmless. The telltale sign that something could be wrong is when the darker color shows up suddenly, or when a dog seems to be in pain or discomfort at the same time. Dogs will naturally lick or nip at an area of the body that feels painful or sore to them – in fact, this is how fur-bald canine “hotspots” are formed. If the dog is leaving the darkened area alone and doesn’t seem to be favoring the other side of his body or moving stiffly, chances are it’s either harmless or only a minor inconvenience, such as a yeast infection. This doesn’t mean, of course, that prompt treatment isn’t needed; only that the dark skin isn’t likely to be a life-or-death issue.
Pet owners may notice the hyperpigmentation in their dog before a vet does, if only by virtue of seeing and interacting with the dog every day. If they’re concerned about it growing or spreading, it’s a good idea to snap a picture with their smartphone to track its appearance over time. This image can then also be shared with a veterinarian’s office through email to determine if an in-person visit is necessary.
Ruling Out Canine Hyperpigmentation Look-Alikes
Primary hyperpigmentation is simply a harmless concentration of melanin. If a dog has primary hyperpigmentation, it:
- Will not fluctuate a great deal from week to week or month to month
- Will not be itchy, painful, or distracting to a dog
- Will not grow darker in short periods of time
- Will not be caused by rashes, bacteria, or skin infections like parasites
- Will not fade wash off of a dog if he is groomed or given a bath
- Will not be caused by sun exposure or sunburn
- Will not be raised up off the skin, like a mole, tumor, or scar
- Will not be able to “transfer” to another dog or pet
It’s important to rule out these “lookalike” skin conditions, as many of these are actually serious concerns that will need medical attention as soon as possible. When hyperpigmentation occurs in any of these instances, it’s considered “secondary” and treated as a symptom of another disease or disorder. Just as humans seek out a dermatologist for the sudden appearance of dark skin or raised moles, so should canines to ensure a long, healthy life.
“Reverse” Hyperpigmentation in Dogs
Some dogs are born with or develop darker patches of skin, either through primary or secondary hyperpigmentation. Others seem to have the opposite effect, experiencing fading or losing color entirely from formerly-dark areas of skin and fur. The causes behind these seemingly drastic color shifts are surprisingly numerous, and like hyperpigmentation, are usually fairly harmless.
“Snow Nose” afflicts dogs like Labradors most often. When it occurs, a formerly-black nose may become splotchy pink or even fade to pink entirely, only to return to black with warmer weather. While the exact causes of the phenomena aren’t known, dogs that display the trait tend to experience it year after year. It’s harmless, and doesn’t represent any loss of sensation for dogs that have it; it’s merely an interesting visual anomaly.
Darker fur and skin can also fade with age, either through being replaced by sparse grey fur around the eyes and muzzle over time, or fur colors looking “washed out.” This is simply a side effect of the canine aging process, and nothing to worry about. In some darker-coated breeds, small injuries like cuts or scratches might also have fur that grows back lighter as the wound heals, though this will usually only be a few small hairs unless the wound is substantial.
Finally, if a dog has “hot spots” that he often scratches or licks, the continual application of his own saliva through licking a spot repeatedly can dull the color of his fur. Some vets will even use these tell-tale color fades to diagnose skin issues and pinpoint where topical salves or treatments should be placed.
Can Hyperpigmentation In Dogs Be Cured?
Even though it’s painless for canines with this unique skin discoloration, some pet parents might not like the aesthetic look of dark patches on their dog’s groin, thighs, and belly. There is, however, no “cure” for primary hyperpigmentation of the skin in dogs – much like human freckles, moles, café au lait spots and beauty marks, it’s a part of a dog’s appearance and likely around for a while, if not for life. Secondary hyperpigmentation, however, can often be cured by treating the root problem: parasites, skin infections, etc. Once the core issue is corrected, the hyperpigmentation is likely to follow suit as the dog heals up.
This is the reason why it’s very important to distinguish between primary and secondary types of skin discoloration. While primary will only affect the dog that shows it, secondary hyperpigmentation may be caused by a topical issue that can be contagious to other household pets or even human owners. When in doubt, ask a professional: a vet will be able to correctly identify an underlying issue in minutes. An owner, on the other hand, may spend worried hours clicking through the internet, only to arrive at an incorrect diagnosis.
As long as a dog is acting normally, and eating, drinking, and eliminating, hyperpigmentation isn’t something the average pet parent needs to worry about. Adding regular checkups, a healthy diet, engaging toys, and wholesome supplements to his lifestyle will help stave off any potential skin issues before they can cause issues with his fur and skin. And remember: dogs are surprisingly adept at communicating issues through body language, scratching, licking, and whining. If there’s a problem, they won’t hesitate to let their humans know if some type of intervention is called for.
- Moriello, Karen A., DVM, DACVD. “Hyperpigmentation (Acanthosis Nigricans) in Dogs.” Merck Manual (merckvetmanual.com), (no publish date), https://www.merckvetmanual.com/dog-owners/skin-disorders-of-dogs/hyperpigmentation-acanthosis-nigricans-in-dogs. Accessed March 16, 2020.
- “Why Is Some of My Dog’s Skin Turning Black?” Dog Health.com, (no publish date), https://www.doghealth.com/health/skin/2482-why-is-some-of-my-dogs-skin-turning-black. Accessed March 16, 2020.
- “Postinflammatory Hyperpigmentation.” ScienceDirect.com, (no publish date), https://www.sciencedirect.com/topics/veterinary-science-and-veterinary medicine/postinflammatory-hyperpigmentation. Accessed March 16, 2020.
- “Loss Of Pigmentation In Dogs.” American Kennel Club (AKC.org), April 26, 2015, https://www.akc.org/expert-advice/health/loss-of-pigmentation-in-dogs/. Accessed March 16, 2020.