If you ran a hand down your cat's back and felt dozens of tiny, crusty bumps, you have probably found miliary dermatitis. It is a skin reaction, not a disease on its own, and the most common trigger is an allergy to flea bites. That holds even when you have never seen a flea on your cat.
The fix starts with flea control for every pet in the home, using products your vet recommends and only cat products on cats. Your vet then works out whether fleas are the whole story or whether food, environmental allergies, mites or ringworm are involved.
What miliary dermatitis looks and feels like
The name comes from the Latin word milium, which means millet. The bumps are small, round and crusted, a lot like millet seeds scattered under the fur. They are often easier to feel than to see.
Vets describe it as many small papules (raised bumps) and crusted papules, either in one area or spread over the body. You will usually find them on:
- the back, especially the lower back and the base of the tail
- the neck
- the face and ears
- the flanks and belly
The rash itches, so affected cats lick, bite and scratch at it. Some cats twitch or start grooming as soon as you touch the spot. Over time the coat gets thin and patchy where the cat keeps licking, and the bumps turn into small scabs, either from the reaction itself or from scratching. If the skin gets infected, the scabs can look more like pimples or pustules.
Bumps on the back are not cat acne. Feline acne lives on the chin and lips. If the crusty bumps are along your cat's back, neck or tail base, think fleas and allergies first. Our guide to cat acne on the chin covers the difference.
It's a sign, not a disease
Miliary dermatitis is what vets call a reaction pattern. The skin reacts in the same way to many different triggers, so two cats can have identical bumps for completely different reasons. That is why the bumps alone do not tell you, or your vet, what is going on. The cause has to be found and treated, or the bumps come back. It is also one of the most common skin problems vets see in cats.
Common causes
Cause | Clues | Can it spread to other pets or people? |
|---|---|---|
Flea allergy (the most common cause) | Bumps over the back, neck and tail base; very itchy; fleas often not seen | Fleas move to the other pets in the home. The allergy itself is not contagious. |
Food allergy | Small crusty bumps, often with itching around the head and neck; itch level stays about the same all year | No |
Environmental (airborne) allergies, called feline atopic skin syndrome | Itch that can be seasonal or year-round; diagnosed only after fleas, parasites and food are ruled out | No |
Mites and lice: Cheyletiella ("walking dandruff"), Notoedres (feline scabies), ear mites | Cheyletiella: crusts and small bumps along the back, flaky skin. Notoedres: crusts that start on the ears, head and neck | Yes. Cheyletiella spreads easily between pets and often to people. Notoedres spreads cat to cat. |
Ringworm (a fungal infection, not a worm) | Bald, scaly, crusted patches with broken hairs, often on the face, ear tips, tail and feet; some cats get small itchy bumps | Yes, often to people |
Rarer causes | Immune-mediated disease such as pemphigus foliaceus, nutritional deficiencies, skin infections, and occasionally tumors | Depends on the cause |
Flea allergy is the big one. A cat that is allergic to flea saliva can react strongly to a single bite, which is why one flea you never see can keep a cat itchy. Read more in our guide to flea allergy dermatitis.
Miliary dermatitis itself is not contagious. Whether anyone else in the house is at risk depends on the cause. If your cat has ringworm or mites, your vet will tell you what to do for the other pets and the people in the home, and washing your hands after handling the cat is a good habit. See our pages on ringworm in cats and mange in cats.
Why you may never see a flea
Owners often say, "But my cat doesn't have fleas." Very allergic cats groom so thoroughly that the fleas are gone before anyone spots them, as the Merck Veterinary Manual notes. VCA puts it simply: live fleas are seldom seen on cats.
What you can sometimes find is flea dirt: tiny reddish-black specks in the coat or bedding. Put them on a damp white paper towel. Flea dirt is digested blood, so it dissolves into a reddish-brown smear. A flea comb makes the specks easier to find. More on that in flea dirt on pets.
Indoor cats are not off the hook. Even pets that only go outside for a few minutes can pick up fleas, and people can carry fleas into the house. Stray cats and dogs and wild animals can also bring fleas into your yard.
Fleas matter for people as well. The bacterium behind cat scratch disease, Bartonella henselae, spreads to people through the scratch of a cat that has been infected by fleas, according to the CDC. Our cat scratch fever post has the details.
Flea control for every pet in the home
If one pet is treated and the dog, the other cat or the house is not, the fleas just wait it out. Merck says prevention and treatment of flea allergy require treating the affected pet, the other pets in the household and the environment. The Companion Animal Parasite Council recommends year-round flea control for all cats and notes that every pet in the home must be treated to get an infestation under control.
What that looks like in practice:
- Every dog and cat in the house gets flea control, not only the itchy one.
- Year-round, not just in summer. Fleas develop indoors in carpets, under furniture and along baseboards, and in warm climates they stay active all year.
- Use a product your vet recommends. Options for cats include topical spot-ons, oral products and collars made for cats. Merck notes the most effective products are sold by veterinarians.
- Check the label. It should match your pet's species, life stage and weight, as the FDA advises.
- Treat the house. Vacuum where your pets sleep and rest, including under and inside sofas, and wash pet blankets, throw rugs and carriers. Flea eggs and larvae collect in bedding, carpets and furniture. Ask your vet before using any household insecticide around cats.
You may still see an occasional flea for a while after you start, until the ones developing in the house are gone.
Never put dog flea products on your cat
This is the mistake that turns an itchy cat into an emergency. The FDA's rule is short: if the product is for use on dogs, don't use it on cats. Some dog spot-ons contain permethrin, and cats appear to be more sensitive to this group of insecticides (pyrethroids) than other pets.
In one Australian study of 42 poisoned cats, most had a dog permethrin spot-on put directly on them, despite clear label warnings. The authors point to how easy these products are to buy without veterinary advice. Tremors or muscle twitching showed up in 86% of the cats, and the authors note the poisoning can be fatal. One cat in the study got sick after the product went on a dog it lived with, so ask your vet which flea product is safe for a dog that shares a home with cats.
Call your vet or an emergency clinic right away if a dog flea product touched your cat, or if your cat shows any of these after any flea product:
- tremors, twitching or seizures
- wobbling, stumbling or poor coordination
- drooling, vomiting or diarrhea
- not eating, or acting dull and depressed
If the product is a collar, take it off. Have the package with you when you call. If you can't reach your vet, the ASPCA Animal Poison Control Center at (888) 426-4435 and the Pet Poison Helpline at (855) 764-7661 are open 24/7. A consultation fee may apply.
What your vet will do
Finding the cause takes some detective work, and it often happens in steps. Your vet will usually start with the most common cause and work outward.
- History and exam. Your vet will ask how itchy the cat is, when it started, whether it gets worse in certain seasons, what flea product every pet is on, what the cat eats, and whether any other pet or person in the house is itchy or has a rash. An itchy person or pet in the home points toward ringworm or mites.
- Flea check. A careful flea comb through the coat, and the damp paper towel test on what comes out.
- Skin tests in the clinic. Skin scrapings and tape or swab samples (cytology) look for mites, bacteria and yeast. An ultraviolet lamp and a fungal culture of plucked hairs check for ringworm. If someone in your home is very young, pregnant, older or has a weakened immune system, or your cat has had a lot of steroid treatment in the past, tell your vet, since that can move ringworm testing up the list.
- A flea and parasite trial. Strict, vet-recommended parasite control for every pet in the home. If the bumps settle, fleas or mites were likely the cause.
- A food trial. If fleas and infections are ruled out, your vet may put your cat on an elimination diet: a hydrolyzed or new-protein food and nothing else, not even treats. VCA notes that even licking a plate clean can spoil the result. The trial usually runs 8 weeks or more (Merck says up to 3 months), and your vet sets the length.
- Biopsy and blood work if the picture is still unclear, plus referral to a veterinary dermatologist for hard cases.
Your vet diagnoses environmental allergies by ruling everything else out. After that, skin or blood allergy tests help choose what goes into the cat's allergy shots (immunotherapy).
Treatment follows the cause:
- flea control for every pet and the home, or treatment for mites or ringworm
- the elimination diet, then avoiding the food that causes the reaction
- treatment for any skin infection caused by scratching
- itch relief your vet chooses, such as anti-inflammatory medicine for a short time while the main treatment starts to work, antihistamines, omega-3 fatty acid supplements, calming or antiseptic sprays, or a medicated shampoo your vet recommends
- long-term management, including allergy shots, for cats with environmental allergies
Your vet picks the medicine, the dose and how long to use it. Vets rule out infection, mites and ringworm before they rely on anti-itch medicine, so leftover medicine from a previous flare is not a shortcut.
Skip the home remedies
Coconut oil rubs, Epsom salt soaks, oatmeal baths and warm towel wraps show up a lot online. None of them removes the cause, whether that is fleas, a food allergy, mites or ringworm, so the bumps keep coming back. Cats are fastidious groomers, so anything you put on the coat tends to end up in the cat. Ask your vet before you bathe your cat or put any product on its skin. If a bath would help, your vet can recommend a medicated shampoo.
When to call your vet
What you notice | What to do |
|---|---|
A dog flea product touched your cat, or tremors, seizures, wobbling, drooling or vomiting after any flea product | Call now |
New crusty bumps, scabs, hair loss, or your cat is licking, scratching or grooming more than usual | See your vet soon |
Bumps that look infected (pimples, pus, raw or swollen skin), or bumps that don't improve after starting flea control | See your vet soon |
Someone in the house has an itchy rash, or another pet is itching too | See your vet soon, and mention it (ringworm and mites can spread) |
The skin has cleared and you want to review the year-round flea plan or diet for all your pets | Mention at your next visit |
Outlook
The outlook is very good for most cats. When fleas are the cause, steady flea control for every pet in the home usually brings the skin back to normal.
Allergies are managed rather than cured. A cat with a food allergy usually stays comfortable as long as it avoids the trigger food. Environmental allergies are lifelong and need long-term management and regular checkups, and flare-ups can happen. Consistency is what works: the same flea control all year for every pet, and nothing outside the diet your vet set.
Quick answers
Is miliary dermatitis contagious? Not by itself. The cause can be: fleas move between pets, and ringworm and some mites can spread to other animals and to people.
My cat lives indoors. Can it still be fleas? Yes. Fleas get into homes on other pets and on people, and even short trips outside are enough.
Will it come back? It can, if the cause comes back. Gaps in flea control are the most common reason. Cats with allergies may have flare-ups and need ongoing care from your vet.
Can I treat it at home? Your part at home is flea control for every pet and the house, with vet-recommended products, and sticking to the plan. Finding the cause and choosing medicines is your vet's job.
Originally written by Dr. Stavroula Tsovolou. Updated by the I Love Veterinary editorial team.
Sources
- Merck Veterinary Manual: Fleas of Cats
- Merck Veterinary Manual: Flea Allergy Dermatitis in Dogs and Cats
- Merck Veterinary Manual: Feline Atopic Skin Syndrome
- Merck Veterinary Manual: Allergies of Cats
- Merck Veterinary Manual: Ringworm (Dermatophytosis) in Cats
- Merck Veterinary Manual: Mite Infestation (Mange, Acariasis, Scabies) of Cats
- Merck Veterinary Manual: Plant-Derived Insecticide Toxicosis in Animals
- VCA Animal Hospitals: Miliary Dermatitis in Cats
- VCA Animal Hospitals: Food Allergies in Cats
- Bettenay SV. Feline Cutaneous Reaction Patterns: Practical Hints and Tips. WSAVA World Congress 2008 (VIN)
- Clinician's Brief: Miliary Dermatitis
- U.S. Food and Drug Administration: Safe Use of Flea and Tick Products in Pets
- U.S. Environmental Protection Agency: EPA Evaluation of Pet Spot-on Products
- Boland LA, Angles JM. Feline permethrin toxicity: retrospective study of 42 cases. J Feline Med Surg 2010
- Companion Animal Parasite Council: Fleas
- CDC: About Bartonella
- ASPCA Animal Poison Control Center
- Pet Poison Helpline
This article is for general information and is not a substitute for advice from your veterinarian.
