Why is my dog itching?

While an occasional itch is a common occurrence for dogs, frequent scratching, along with bum scooting, excessive chewing and biting, or redness of the skin, are signs of conditions that may need medical treatment. Not only is itching a huge annoyance for dogs, but can result in hair loss and sore, scabby skin lesions, darkened skin tone and skin infection when left untreated. The medical term for itching is ‘pruritus’, and is one of the most common reasons for dogs to visit the veterinary surgery.

The most common causes of pruritus are allergies, parasites (mites) and skin infections (fungal or bacterial). More rarely, skin cancers and autoimmune diseases may be the cause.

PARASITES

There are several mites that can cause skin problems:

Sarcoptic mange mites burrow in the skin and create a severe itch, especially on the belly, elbows, hocks and ear flaps (also called fox mange). Note this is a zoonotic infection and can be passed onto humans.

Demodex mites cause patchy hair loss anywhere but produce minimal itch; this is more common in puppies.

Cheyletiella mites produce a severe flaky dandruff and itchy coat.

Ear mites create smelly, itchy ears and are more commonly seen in puppies. In general, mites are much less of problem than they used to be, as many modern flea treatments will also kill some mite species.

ALLERGY

Your dog could develop allergies when they are repeatedly exposed to a material – the ‘allergen’ – and the immune system overreacts to this. This causes inflammatory substances to be released, which in turn cause itchiness. Allergies can occur at any stage during your dog’s lifetime. Some breeds are predisposed to developing allergies, including West Highland White Terriers, Wirehaired Fox Terriers, Golden Retrievers, Labrador Retrievers, Lhasa Apsos, Bulldogs, English Setters, Boxers, Dalmatians and Shar-Peis.

There are many substances that can act as allergens, the incidence of these varies on geographic location and on season of the year.

  • Inhaled allergens, including moulds, pollens and house dust. This is known as ‘atopy’. Signs are often seasonal, especially when pollens are the cause. Atopy is often complicated by secondary fungal infections, pyoderma and ear infections.
  • Flea bite allergy is a reaction to the saliva in flea bites. Whilst many believe the Middle East is too hot for fleas to live, any itchy pets should always be treated for fleas before further investigations or treatments are carried out. Remember once a flea infestation is in the home, it can take months of persistent treatment to clear, so prevention is always better than cure.
  • Contact allergy, which is caused by skin exposure to an irritating substance, such as soaps, household and garden sprays or chemicals. The itching is usually non-seasonal and the distribution will be dependent on what body part is frequently contacting the allergenic substance.
  • Food allergies produce year-round pruritus. It is a common misconception that food allergies always produce gastrointestinal signs. Skin itching is actually the most common presenting sign, either alone or with diarrhoea.

Investigation of allergic skin disease

Your veterinarian will need a complete history of the clinical signs, including the time of year the itching is worst. They will rule out the most common causes such as fleas or parasites before embarking on more complex investigation. Often, the itching may be due to a combination of factors- the dog may be a little allergic to a lot of different things which accumulate to a level that causes the dog to start itching (the ‘pruritic threshold’). 

Treatment of allergic skin disease

Reducing the exposure to some or all the identified allergens is the treatment priority and may be enough to lower the dog under the pruritic threshold. This can be in the form of flea treatment and/ or a low allergen diet such as Royal Canin Hypoallergenic or Anallergenic. This concept of pruritic threshold explains why a dog identified as allergic to inhaled environmental allergens, may also benefit from a low allergen diet.

Royal Canin therapeutic diets are high in antioxidants, omega-3 and 6 fatty acids which help reduce itching and inflammation associated with allergic dermatitis. These diets have a patented skin barrier complex of A and B vitamins, which helps improve the integrity of the skin, preventing water loss and entry of environmental allergens.

In addition, your vet may recommend a combination of treatments to help manage the itching, which can make him feel a lot better. These include special soothing pet shampoos, food supplements and medical treatment. Allergic dermatitis can take a long time to improve, and in many cases will need long-term management as it is not possible to ‘cure’ the allergy.

INFECTION

Damaged, inflamed skin is more prone to getting infected, this can either be with bacteria or yeasts.

Bacterial infection (Pyoderma)

Pyoderma is an infection of the hair follicles with Staphylococci bacteria. It is extremely common either secondary to another skin problem or in certain susceptible breeds. Pyoderma usually looks like a pimply rash, but sometimes also crusty rings called epidermal collarettes or rapidly enlarging moist crusty lesions called hotspots. Lesions can occur anywhere on the body. Pyoderma is usually treated with antibiotics and topical washes, combined with eliminated the underlying cause.

Fungal infection

Overgrowth of skin Malassezia yeast is another secondary infection that requires its own special treatment. It is a greasy, smelly dermatitis of folded areas like armpits, groin, ears, feet and under the tail. It is usually treated with topical washes and eliminating the underlying cause of the infection.

RARE CAUSES

Lastly, there is an extremely rare skin cancer that causes severe itching. Some autoimmune diseases also have severe skin effects including erosions, scabs and blisters. Neither these, nor any other rare conditions, should be considered until a vet has ruled out the common diseases.

Itchy dogs are incredibly commonplace. The hot humid climate, coupled with cool dry air-conditioned homes in the Middle East can exacerbate itchy skin conditions. Many cases can be readily improved with simple treatment or dietary manipulation, but some may require considerable veterinary input and long-term commitment to treatment on behalf of the owners. Diet is a key factor in treating itchy dogs in all cases.

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