Not all hair loss itches. A dog can go bald across both flanks, with sharply outlined patches and darker skin underneath, and never scratch once. That pattern points away from allergy and towards a short list of other causes, one of which arrives with the shortening days and leaves again in spring.
The question that separates two very different problems
Almost everything written about skin starts with the itch, and for good reason, since that is what sends most owners looking for help. But the first thing we ask about a bald patch is not how bad it looks. It is whether the dog is bothered by it.
If the answer is no, the field narrows sharply. An itchy dog who is pulling their own coat out is a different animal from a dog whose hair is simply not growing back. The first is usually about allergy, parasites or infection. The second is usually about the hair follicle itself, and the causes behind it are hormonal, genetic, seasonal or mechanical.
Getting that question answered honestly at the start saves a great deal of circling. It is also the one piece of information an owner is uniquely placed to give us, because you are the one watching the dog all evening.
The one that comes back every autumn
There is a specific, well-recognised pattern where a dog loses hair over both flanks as the days shorten, holds the bald patches through winter, and regrows the coat in spring. It then does the same thing the following year.
What it looks like is distinctive once you have seen it. The patches sit over the flanks and the lower back, they are often strikingly symmetrical, and the edges are sharply defined rather than fading out. The exposed skin frequently darkens, sometimes considerably, which alarms owners more than the hair loss does. The dog is otherwise completely well, eats normally, and is not remotely itchy.
The breeds most often named are Boxers, Airedale Terriers and English Bulldogs, with Rhodesian Ridgebacks and Staffordshire Bull Terriers reported more recently. It also turns up in the thick-coated northern breeds, including Keeshonds, Schipperkes, Chow Chows, Samoyeds, Siberian Huskies and Malamutes, and in Pomeranians. Most affected dogs are somewhere between three and six years old when it first appears.
The timing is tied to day length rather than to temperature. The current understanding is that the follicle responds abnormally to the ordinary hormonal rhythm that tracks the changing photoperiod, which is why it begins in autumn and why reported cases cluster from November through to March.
There is a local reason this is worth writing about here. The condition is reported mainly north of the forty-fifth parallel, and Vancouver and Surrey sit close to forty-nine degrees. We are well inside the band where it shows up, and our autumn light collapses quickly.
The outcome is reassuring more often than not. Most dogs regrow the coat on their own, commonly over three to eight months, though the reported range is wide and some take much longer. Roughly one dog in five has a single episode and never repeats it. A minority never fully regrow. None of it makes the dog unwell, and for many the honest answer is that it is a cosmetic matter and leaving it alone is reasonable. That is a conversation worth having rather than assuming either way.
What else takes a coat without an itch
Seasonal timing is suggestive, not diagnostic, and several other things produce quiet hair loss.
- An underactive thyroid. Thinning over the trunk and tail, a dull coat, skin that feels cool or thickened, weight gain and a dog who has slowed down. Usually a middle-aged dog, and usually the owner has put the other changes down to age.
- An overactive adrenal gland. Hair loss alongside a pot-bellied look, thin skin, visible blood vessels, panting, and a marked increase in drinking and urinating. The drinking is the detail that should move this up the list quickly.
- Hair that never came back after clipping. Genuinely a thing in plush-coated breeds, where a clipped area simply stalls for months. Harmless, and worth knowing before anyone goes looking for something sinister.
- Pattern baldness, which thins the ears, the chest, the belly or the backs of the thighs in certain breeds and is largely cosmetic.
- Pressure and friction. Elbows, hocks and anywhere a hard floor or a harness rubs.
- Parasites and fungal causes that stay quiet. Both mites and ringworm can strip hair with little or no itch, which is exactly why a bald patch gets sampled rather than guessed at. Skin mites are the cause most often missed here, and they are worth ruling out early.
- Scarring from an old injury or infection, where the follicle is simply gone.
The darkened skin that worries owners in the flank pattern is usually just the skin responding to being uncovered and to low-grade irritation. It is a reaction rather than a cause in its own right, and our guide to hyperpigmentation in dogs sets out what darker skin does and does not mean.
Cats are the exception, and it matters
Everything above assumes you would notice your animal scratching. With cats that assumption fails.
A cat with symmetrical hair loss along the belly, the inner thighs or the flanks has very often removed it themselves, quietly, somewhere you were not watching. The skin underneath can look perfectly normal. Owners describe it as the hair simply falling out, and the giveaway is stubble rather than bare skin, or hair that is broken rather than absent at the root.
So in a cat, non-itchy hair loss should be regarded as itchy hair loss you have not witnessed until proven otherwise. Our guide to over-grooming in cats covers the signs that give it away. Cats do also get genuine hormonal hair loss, which is why the sample still gets taken.
What is worth doing before the appointment
Three things, none of which take long, and all of which make the first visit more useful:
- Photograph it now, and keep photographing it monthly. Use the same angle and the same light. For anything seasonal, a set of photographs across a year is worth more than any description, and it is the thing owners most often wish they had.
- Write down when it started and what the month was. If this has happened before, when did it begin and when did the coat come back? That history alone can make the pattern obvious.
- Note everything that is not the skin. Drinking, appetite, weight, energy, whether they feel the cold more. Quiet hair loss with any of those alongside it points at a hormonal cause, and that changes the urgency.
How we work it out
A bald patch gets sampled rather than guessed at, because several of the causes above look alike from across the room and a couple of them are contagious. That usually means looking at hair and surface samples under the microscope first, and in some cases taking a small skin biopsy, which is the only way to see what the follicles themselves are doing.
Where the history points at a hormone, blood work settles it. Where it points at the seasonal pattern, the diagnosis is often made by excluding the others and then watching what the coat does over the year, which is why those monthly photographs earn their keep.
This is the part of dermatology that has nothing to do with allergy, and it is what our skin and ear conditions service exists for: follicles, hormones, nails, pigment and the hair that simply stops growing. Where the picture is genuinely mixed and an allergic component needs ruling in or out, allergy testing has a place, though it comes after the clinical picture rather than before it. And where an allergic component does turn out to be part of the picture, allergy desensitization is the route that follows from testing rather than something started on spec.
When it is more than cosmetic
Much non-itchy hair loss is a cosmetic matter in a well dog. Speak to your own veterinarian promptly, rather than waiting for a dermatology appointment, if the hair loss comes with any of these:
- Drinking and urinating noticeably more than usual.
- Weight change in either direction without a change in food.
- Lethargy, or seeking out heat and seeming to feel the cold.
- Skin that has become thin, fragile or slow to heal.
- Skin infections that keep returning.
- Open, ulcerated or bleeding areas rather than simply bare skin.
- A cat losing hair anywhere, since the quiet version is usually self-inflicted.
Those point at something systemic, and that is your own veterinarian’s work before ours.
Our hours, and what we are not
We are a referral dermatology practice and we work weekdays only. Our Vancouver location in Mount Pleasant is open Wednesday and Thursday, and our Surrey location at Riverside Heights is open Monday, Tuesday, Thursday and Friday, both 8:00 am to 4:30 pm. We are closed Saturday and Sunday.
We are not an emergency service. Hair loss is never an emergency, but skin can be, so go to your own veterinarian, or to an open emergency veterinary hospital outside their hours, if your pet has a rapidly swelling face, hives spreading quickly, a wound that is bleeding or clearly infected, or skin that is ulcerated and painful. Any difficulty breathing means leaving immediately and having somebody call on the way.
Common questions
My dog goes bald every winter and grows it back every spring. Does that need looking at?
It is worth confirming once, then usually not again. The seasonal pattern is recognisable, but several other causes can imitate it, and the only way to be confident is to exclude them properly the first time. Once that is done and the cycle is established, most owners simply photograph it each year and leave it alone.
The skin underneath has gone very dark. Is that serious?
Usually not on its own. Skin commonly darkens where it has lost its cover or been mildly irritated, and it tends to fade as the coat returns. What matters more is whether the skin is thickened, greasy, smelly or sore, because those suggest something active rather than a simple reaction.
Will the coat definitely grow back?
Most dogs do regrow it, commonly over three to eight months, though the reported range is considerably wider. About one dog in five has only a single episode. A minority never fully regrow, and that is worth knowing in advance so it is not a surprise. None of it makes the dog unwell.
Is this something I caused?
No. The seasonal pattern appears to be inherited and tied to day length, which is why it concentrates in particular breeds and at our latitude. Nothing in the diet, the grooming routine or the household brought it on.
My cat is losing hair but I have never seen her scratch.
Assume she is doing it out of sight until we have looked. Cats groom hair off in private, and the skin underneath often looks normal, so the absence of visible scratching tells us very little. Look for stubble rather than bare skin, and bring her in.
Do I need a referral to see you?
Most clients arrive on a referral, which is the smoothest route because your own clinic can send the file ahead. You are also welcome to approach us yourself, and we will loop your veterinarian in afterwards. Either way, bring the photographs and a note of anything already tried.
Speak to the team at VetDERM Clinic
If your dog has bald patches that do not itch, a coat that has not come back, or a pattern that repeats every autumn, request a consultation and bring your photographs. For anything sudden, painful or rapidly worsening, see your own veterinarian or an open emergency veterinary hospital first, because we work weekdays and are not an emergency service.
Published by the team at VetDERM Clinic.
This article is educational in nature and is not a replacement for hands-on assessment of your own pet by a veterinarian.
VetDERM Clinic
Vancouver: 15 East 3rd Avenue, Vancouver, BC V5T 1C5 (Mount Pleasant), open Wednesday and Thursday
Surrey: 14823 108 Avenue, Surrey, BC V3R 1W2 (Riverside Heights), open Monday, Tuesday, Thursday and Friday
Phone: (604) 564-2214
Email: info@vetdermclinic.com
Hours: 8:00 am to 4:30 pm at both locations; closed Saturday and Sunday
