Itching in dogs: symptoms, tests and treatment

Overview

The medical term for itching is pruritus. It may affect a small area or the whole body. Scratching is not the only way dogs express itchy skin. Rubbing and rolling can also be signs.

Skin disease is not always itchy from the start. Itching may begin only after a secondary bacterial or yeast infection develops. The original source of irritation may already have disappeared. Treating the symptom therefore requires checking the skin for current infection too.

Long-term allergic skin disease can affect quality of life for both the dog and family. Finding the underlying cause may require several follow-up visits.

Causes

Fleas and skin mites are among the first causes to investigate. Sarcoptic mange can cause sudden, intense itching. Lice can also cause varying degrees of itching. Cheyletiella mites cause itching and scaling, particularly in puppies.

Bacterial skin infection can cause itching. Malassezia yeast overgrowth can worsen the same symptom. Several causes of infection may be present at once. Infection can maintain itching alongside underlying allergic disease.

In flea allergy, a dog develops a marked skin reaction to flea saliva. Foods can cause allergic itching. Pollens, moulds and dust can also trigger it. Seasonal symptoms may reflect allergen exposure that varies with the seasons.

In atopic disease, defects in the skin barrier can contribute to disease development. Changes in the balance of skin microbes also play a role. Among itch-signalling substances, IL-31 can activate sensory nerves in the skin. Some anti-itch medicines act on this signalling pathway.

Risk factors

External parasites can cause itching at any age. Atopic disease involves inherited susceptibility. The living environment and conditions also affect its onset. A breed's predisposition to atopic disease may vary with genetic background and geographical area.

Contact with other animals can expose a dog to contagious external parasites. An animal with sarcoptic mange can also contaminate shared grooming tools or sleeping areas. Existing allergic skin disease predisposes to further flare-ups, for example during infection.

Food allergy can start at any age. No clear sex predisposition to atopic disease is known. Indoor allergens, such as house dust mites, can maintain year-round allergic itching.

Typical symptoms

Itching can show as repeated actions directed at the skin. The location of itchy areas may offer clues to the cause.

• Scratching: more frequent or forceful scratching than usual.
• Licking: repeatedly licking the paws, for example.
• Chewing: gnawing or nibbling an itchy area.
• Rubbing: rubbing the skin or face against a surface.
• Hair loss: affected skin may develop thin-haired or bald patches.
• Scaling and odour: dermatitis may cause scaling and an unusual smell.

Atopic disease often affects the paws, face, ears, armpits and abdominal skin. Recurrent ear inflammation may be its only visible sign in some dogs. Redness can be an early change in allergic inflammation.

Around 19–27% of food-allergic dogs also have vomiting, loose stools or diarrhoea. Atopic skin may show bloody crusts and scratch marks. Many atopic skin lesions result from the dog's own scratching and other actions directed at the skin.

Complications and consequences

Constant scratching can break the skin surface. Long-term scratching and chewing can thicken it. Extra dark pigment may accumulate in the same areas. The coat can thin or become completely bald in places.

Constant itching causes prolonged stress. It may also cause behavioural changes such as irritability. Secondary bacterial or yeast infection can further worsen an allergic dog's symptoms. Atopic symptoms can usually be controlled with long-term treatment.

Diagnosis at the vet

The vet asks when itching began and where it first occurred. Seasonality and parasite control are important parts of the history. The effects of previous medication also help interpret symptoms. Concurrent itching in other animals or people may suggest external parasites.

A full skin examination includes the paws and skin folds. The ears are checked even if the owner has not noticed ear itching. Flea combing forms part of the initial examination. Skin scrapings look for parasites such as sarcoptic mange mites and Demodex mites.

A negative scraping does not always rule out sarcoptic mange. Response to parasite treatment may then form part of the investigation. Skin cytology checks for bacteria and yeast. When ear inflammation is suspected, cytology of ear discharge is also a basic investigation.

Atopic disease is diagnosed from a compatible clinical picture and exclusion of other causes. Skin or blood allergy tests show sensitisation and exposure; they do not confirm atopic disease on their own. They are used particularly to choose allergens for immunotherapy. Food allergy is not diagnosed with the same allergy tests.

Yeast numbers on cytology do not necessarily match skin disease severity. A thorough skin examination may require sedation in a painful dog or one resisting handling.

A dietary trial when needed

Food allergy is investigated with a veterinary-planned elimination diet. The trial uses a carefully selected hydrolysed or novel-protein diet. A diagnostic dietary trial is recommended to last 4–12 weeks. If symptoms improve, a food challenge helps confirm the diagnosis.

Treats outside the diet can interfere with interpretation. Food allergy and atopic disease cannot reliably be distinguished by skin lesion location alone. Food-allergic dogs may also have digestive symptoms.

Serum, saliva or hair tests do not replace a dietary trial for diagnosing food allergy either. Ordinary commercial food may contain unlisted ingredients that interfere with the trial.

Treatment

Treating the cause and itching together

The vet chooses treatment according to the confirmed or likely underlying cause. A confirmed flea infestation is treated with a suitable canine parasite product. Household animals in contact with the dog are also treated when needed. Treating bacterial and yeast infections forms part of care alongside itch control.

Malassezia dermatitis may be treated with a topical or systemic antifungal. Anti-itch medication may be needed while investigations continue. An anti-itch medicine alone does not replace appropriate treatment of active skin infection. The response to treatment for allergic skin disease is usually assessed around 14 days after starting.

If anti-itch medication gives an incomplete response, skin cytology may need repeating. Bacterial infection responding poorly to a systemic antibiotic may require culture before another antibiotic is chosen.

Medication for allergic itching

A fast-acting glucocorticoid may be chosen for a severe allergic flare-up. Topical glucocorticoid treatment may also be used for localised lesions. A JAK inhibitor is one option for controlling allergic itching. Antibody treatment targeting IL-31 can also relieve atopic itching.

Medication choice depends on lesion type, severity of inflammation and individual response. Ciclosporin can take up to four to six weeks to produce a clinical effect. Antihistamines offer little help in controlling a severe atopic flare-up. However, they may support other treatment in some dogs with chronic symptoms.

Fatty acid supplements are not a quick solution for atopic itching. Their effect can take up to two months to appear. A response to atopic immunotherapy may develop over three to 12 months. Immunotherapy aims to alter the dog's response to individually selected allergens.

Fatty acids are used particularly to support other medication.

In atopic disease, controlling a flare-up is followed by maintenance aimed at reducing further inflammatory episodes. The same medicine or combination does not suit every atopic dog. If previously effective treatment stops helping, the skin and basic investigations are reassessed.

During a sudden atopic flare-up, flea protection is also checked to ensure it is current. New or worsening skin and ear infections are investigated too.

Prevention

Where flea risk is high, animals can be protected with long-acting control products. With an infestation, the animals' environment may also need cleaning. Bathing an atopic dog can reduce allergens accumulating on the skin. Care supporting the skin barrier can form part of flare-up prevention.

In confirmed food allergy, the goal is to avoid foods causing symptoms. Controlling secondary skin and ear infections reduces factors that worsen atopic disease. Completely avoiding all environmental allergens can be difficult. Some kennel club guidance advises against breeding atopic or allergic dogs.

Important for dog owners

Record where itching started and how its location has changed. Note whether flare-ups are seasonal. Mention previous parasite treatments and their effects. Planning requires details of all previous treatments for itching.

Itching can be monitored on a scale of one to ten, for example. On this scale, ten means constant itching. Assessment includes licking, chewing and rubbing as well as scratching. A good response to corticosteroids does not identify the cause.

During a dietary trial, avoid treats outside the agreed diet. Stopping several medicines at once can make treatment response harder to interpret. Glucocorticoids can increase appetite. They can also increase thirst and urination.

Treatment choice considers practical administration at home alongside safety. Quality of life for the dog and family forms part of long-term treatment goals. Recurrent skin symptoms can also reflect a new infection or another aggravating factor.

Glucocorticoids can also suppress the adrenal glands' own function. They are associated with an increased risk of diabetes. The risk of secondary urinary tract infection may also rise.

Flavoured oral parasite medicines also need consideration during a dietary trial. Eating cat food can interfere with the trial too.

Frequently asked questions

Does itching always mean allergy?

No: parasites and infections are also common causes. Itching may begin with a secondary infection in previously non-itchy skin. The skin and coat are therefore examined before an allergy diagnosis is made. A dog can have both bacterial and yeast infection at the same time.

Can a dog have parasites despite a negative skin scraping?

Yes: sarcoptic mange mites are not always collected in a skin scraping. The vet may then assess the response to parasite treatment. Concurrent itching in other animals or people also offers a clue to possible infestation. Sarcoptic mange can also cause mild or almost no symptoms.

Is changing food enough to investigate itching?

Food allergy investigation relies on a carefully conducted dietary trial. A diagnostic trial usually lasts 4–12 weeks. Treats are also restricted to the agreed diet. If symptoms improve, a food challenge helps confirm the diagnosis. Foods previously eaten are considered when selecting the diet.

Will an antihistamine help my dog's itching?

Antihistamines have very little effect in controlling an acute atopic flare-up. Some dogs with chronic symptoms may benefit from them as part of other treatment. The vet chooses suitable medication according to the dog's circumstances. Skin infection needing treatment can also maintain itching.

How quickly should treatment help itching?

The response to allergic skin disease treatment is often assessed around 14 days. Not all treatments work equally quickly: ciclosporin's clinical benefit may develop over four to six weeks. Treatment choice considers skin lesion severity as well as itching.