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Why is my dog scratching? 8 causes and when to see a vet
A dog most often scratches because of fleas, an allergy or a skin infection. A vet finds the cause step by step. How do you know when not to wait? 8 causes.
It is late in the evening, the flat is quiet and from the rug comes a rhythmic scratching. A moment later, paw licking, then scratching again. Every dog scratches now and then, but when it repeats day after day, the itch usually has a reason, and it can be found. This article will show you where to look and when not to wait any longer.
- A dog that keeps scratching most often has fleas or other parasites, an allergy (to the environment or to the food) or a skin infection. Less often the skin is irritated by a substance the dog touches.
- The cause cannot be guessed from how the skin looks, because the signs of different causes often overlap. That is why a vet rules out one possibility after another.
- According to a review of studies, an allergy to an ingredient in the food turns up in 9 to 40% of dogs with itching. It is checked with an elimination diet that lasts at least 8 weeks.
- Scratched skin with pus, a quickly growing sore, swelling of the muzzle or lethargy should be dealt with by a vet straight away.
- Do not start medicines, creams or supplements on your own. They can mask the cause and prolong the problem.
Is it normal for a dog to scratch, and when does it become a problem?
Occasional scratching is normal. A problem begins when the itch lasts or keeps coming back, your dog cannot sleep because of it or changes appear on the skin. Itching (technically pruritus) is an unpleasant sensation on the skin that makes a dog scratch. According to the guidelines by Hensel et al. (2015), it also includes licking, chewing, dragging the bottom along the ground and shaking the head.
There is no fixed number of times a day a dog may scratch. So watch for changes: it scratches more than before, it wakes up because of it, it has red skin, scales, hair loss or scabs.
What are the most common causes of itching in dogs?
The most common causes of itching in a dog are parasites, allergies and skin infections, and less often skin irritation, stress or boredom. The table is an overview, not a guide to determining the cause, because the signs often overlap and one cause can set off another.
| Cause | What is typical | What a vet usually does |
|---|---|---|
| 1. Fleas (allergy to the bite) | Itching and thin fur at the base of the tail and on the hind legs | Examination of the coat, flea control plan |
| 2. Sarcoptic mange and other mites | Very intense itching, scabs on the ears, elbows and belly | Skin scrapings, trial treatment |
| 3. Environmental allergy (atopy) | Usually starts before the age of 3, itchy paws, ears and belly | Ruling out other causes, a long-term care plan |
| 4. Allergy to an ingredient in the food | Itching all year round, sometimes also diarrhoea or frequent bowel movements | Elimination diet |
| 5. Skin infection (bacteria, yeast) | Pus-filled pimples, scabs, smell, greasy skin | Skin impression under a microscope, treatment of the infection |
| 6. Hot spot | A quickly growing moist, painful sore | Treatment and a search for the trigger |
| 7. Contact irritation | Itching in the places that touch the irritating substance | Finding out what irritates the skin |
| 8. Boredom, stress or pain | Licking and chewing without obvious skin changes | Ruling out skin causes |
When are fleas and mites to blame for itching?
A vet considers fleas and mites first: according to the approach of Hensel et al. (2015), the examination starts by thinking about fleas and then about other parasites, for example sarcoptic mange mites. Flea allergy (flea allergy dermatitis) is an allergic reaction to proteins in flea saliva. According to VCA Animal Hospitals, even a single bite can set off itching and make it last several days. It typically shows up as itching and hair loss from the middle of the back to the base of the tail and the hind legs.
According to VCA Animal Hospitals, fleas multiply most in warm weather, but they can appear at any time of the year. Hensel et al. (2015) add that even where fleas are not very common, a vet should think about whether the dog has travelled or been in contact with animals from areas where fleas are common. That is why the vet usually starts by going through the coat with a flea comb.
Mange caused by the sarcoptic mange mite is, according to the Merck Veterinary Manual, contagious between dogs through touch, but also via combs, brushes, towels and blankets. The itching is very intense, and the changes usually begin on the belly, chest, ears, elbows and hocks. The mites are often not found in a skin scraping, and that is why Hensel et al. (2015) recommend trial treatment for very itchy dogs.
How can you tell a food allergy from an environmental allergy?
An environmental allergy (atopic dermatitis) is, according to Hensel et al. (2015), a common inflammatory and itchy skin disease that some dogs are born prone to. A food allergy and an environmental allergy cannot be reliably told apart by how the skin looks. According to the recommendations of Hensel et al. (2015), the skin signs of both can be the same, and that is why a food allergy is confirmed only by an elimination diet.
- 9 to 40%of dogs with itching had an allergy to an ingredient in the food (the range across studies).Olivry and Mueller, 2017
- 8 weeksis the shortest length of a strict elimination diet according to the recommendations for dogs with atopic dermatitis.Hensel et al., 2015
- before 3 yearsof age is when the first itching in atopic dermatitis usually appears, which is one of the criteria for suspecting it.Hensel et al., 2015
- several daysof itching can follow even a single flea bite in a dog with flea allergy.VCA Animal Hospitals
There are a few hints, though. Hensel et al. (2015) state that itching in atopic dermatitis can be seasonal (for example because of pollen) or all year round (because of house dust mites, and in food allergy because of the food). According to them, diarrhoea, soft stool, flatulence or more frequent bowel movements tend to show up in dogs with a food allergy. The link between the tummy and the skin in dogs is covered in detail by the article Tummy and skin: how a dog’s gut relates to its skin.
An elimination diet is a strict menu with a protein your dog has not eaten before, or with a hydrolysed protein, and nothing else, not even treats. A vet runs it. According to the Lewis et al. (2025) study, more than half of the dogs with a diagnosed food allergy needed longer than 4 weeks for the first improvement. So do not give up on it after a week.
When does an infection cause itching, and what is a hot spot?
Skin infections are common in itchy dogs. According to the Merck Veterinary Manual, they usually develop as a consequence of another problem, for example parasites, an allergy or an injury to the skin. According to Hensel et al. (2015), bacterial infections (Staphylococcus pseudintermedius) are common in dogs with atopic dermatitis and are often recognised by pus-filled pimples and circular scaly rims. A vet confirms them with a skin impression under a microscope. Yeast infections with Malassezia are described in the guidelines by Bond et al. (2020): yeasts normally live on the skin and cause an infection when they overgrow.
According to the Merck Veterinary Manual, pus-forming skin infections often come back when the trigger, for example an allergy or parasites, is not found.
A hot spot is a moist, reddened and painful sore that develops when a dog scratches or chews the skin raw. According to VCA Animal Hospitals, within a few hours it can grow from a dot to the size of a palm. The trigger is often an allergy, an insect bite, an ear infection, a matted coat or boredom with licking. Never underestimate a hot spot: it always belongs with a vet.
Can the environment, stress or boredom irritate the skin?
The skin can also be irritated by the environment, stress or boredom, but a vet considers them only after ruling out parasites, allergies and infections. Contact dermatitis is irritation of the skin by a substance the dog touches. According to the guidelines by Hensel et al. (2015), it is among the causes of itching that a vet distinguishes. It can be cleaning products, shampoos, plants or, in winter, road salt. The article Winter paws: salt, licking and cracked pads is about salt and paws.
According to VCA Animal Hospitals, licking and chewing can get worse from boredom, and a hot spot can also be set off by joint problems or inflamed anal glands. We do not know how many dogs scratch only because of stress or boredom, as there is no reliable figure. That is why a vet gets to this cause only at the end.
What can you do at home before you see a vet?
At home you can help your dog by observing carefully and not trying anything on your own. The aim is to bring your vet as much information as possible.
- Check the skin. Part the fur on the belly, in the armpits, behind the ears and between the toes. Look for redness, scabs, pus and smell.
- Look for fleas. Run a flea comb through the coat, especially at the base of the tail. Black dots that turn red when moistened are usually flea dirt.
- Keep a diary. Write down when and where your dog scratches, what it ate, where it walked and what has changed (food, washing powder, a new blanket).
- Photograph the changes. Photos from different days show your vet how things have developed better than a description.
- Do not apply or give anything. Do not start human creams, medicines or herbal baths. They can irritate the skin and distort the findings.
- Do not change the food because of itching. A change from one day to the next catches the gut off guard and makes the examination harder. You can find out how to switch gradually in the article Switching dog food: a 7 to 10 day plan.
A microbiome analysis does not determine the cause of itching. You can find out what it shows and what it does not in the article Dog microbiome test: what a stool analysis can show.
What should you take away from this?
Itching in a dog can have several causes at once, and a vet rules them out one at a time: first parasites, then infections, then allergies. What is certain is that occasional scratching is normal, repeated scratching is not, a hot spot belongs with a vet and an elimination diet takes patience. If the article helped you, save it and send it on to a friend whose dog keeps scratching.
Frequently asked questions
Why does my dog keep scratching even though it has no fleas?
Fleas are not the only cause. Itching can be caused by mange, an allergy to the environment or the food, a skin infection or irritation. A dog can have a flea allergy even without visible fleas. A vet determines the cause by ruling out one thing after another. According to Hensel et al. (2015), the vet rules out fleas and other parasites first, then skin infections and finally a food allergy.
Is it normal for a dog to scratch every day?
Occasional scratching is normal, but repeated scratching or licking every day is not. If your dog scratches more than before, cannot sleep because of it or has red skin, scabs or thin fur, book an examination with your vet to find the cause. Photos of the skin and a diary of the itching will help your vet judge how the problems are developing.
How do I recognise a food allergy in a dog?
You cannot reliably tell from how the skin looks. According to the recommendations by Hensel et al. (2015), it can be ruled out only by an elimination diet, which lasts at least 8 weeks and is run by a vet. Diarrhoea or more frequent bowel movements tend to show up in food allergy. According to the Lewis et al. (2025) study, more than half of the dogs with a food allergy needed longer than 4 weeks for the first improvement.
What can I give my dog for itching?
Nothing on your own. Human creams and medicines can harm your dog and mask the cause. Because itching can be caused by a parasite, an allergy or an infection, each cause needs different treatment. What to give your dog is always decided by a vet according to the cause. If there is swelling of the muzzle, hives or laboured breathing, call your vet straight away.
What is a hot spot, and can I treat it at home?
A hot spot is a moist, reddened and painful sore left after scratching. According to VCA Animal Hospitals, it can grow to the size of a palm within a few hours. Do not treat it on your own. Show it to a vet, who will find the trigger; otherwise it will come back. The trigger is often an allergy, an insect bite, an ear infection or a matted coat.
Can mange pass to people?
Yes. According to the Merck Veterinary Manual, canine mange can pass to a person who is in contact with the infected dog. If you suspect mange, contact your vet and limit your dog’s contact with other dogs. Mange also spreads through combs, brushes, towels and blankets that the infected dog has used.
Sources
- Hensel P, Santoro D, Favrot C, Hill P, Griffin C (2015). Canine atopic dermatitis: detailed guidelines for diagnosis and allergen identification. BMC Veterinary Research. doi.org/10.1186/s12917-015-0515-5
- Olivry T, Mueller RS (2017). Critically appraised topic on adverse food reactions of companion animals (3): prevalence of cutaneous adverse food reactions in dogs and cats. BMC Veterinary Research. doi.org/10.1186/s12917-017-0973-z
- Lewis TP, Moore GE, Laporte C et al. (2025). Evaluation of hydrolyzed salmon and hydrolyzed poultry feather diets in restrictive diet trials for diagnosis of food allergies in pruritic dogs. Frontiers in Veterinary Science. doi.org/10.3389/fvets.2025.1560806
- Bond R, Morris DO, Guillot J et al. (2020). Biology, diagnosis and treatment of Malassezia dermatitis in dogs and cats: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology. Veterinary Dermatology. doi.org/10.1111/vde.12809
- VCA Animal Hospitals. Flea Allergy Dermatitis in Dogs. vcahospitals.com/know-your-pet/flea-allergy-dermatitis-in-dogs
- VCA Animal Hospitals. Hot Spots in Dogs. vcahospitals.com/know-your-pet/hot-spots-in-dogs
- Merck Veterinary Manual. Mange in Dogs and Cats. merckvetmanual.com
- Merck Veterinary Manual. Pyoderma in Dogs and Cats. merckvetmanual.com
This article is educational and does not replace a veterinary examination. If you are not sure, ask your vet.
This article was proofread with the help of AI. This is a translation from Czech, so it may contain inaccuracies.