Pruritus (Itchiness) in Dogs

Overview of Pruritus (Itchiness) in Dogs

If your dog spends a large portion of his time scratching, he may have a condition known as pruritus, or itching, an unpleasant sensation that causes your dog to scratch or bite at himself. It is caused by chemical reactions that occur in the skin and stimulate the nerves, causing the brain to feel the itch. In fact, the act of scratching itself may stimulate these inflammatory reactions in the skin and make the condition worse. Any skin condition that causes inflammation can cause pruritus.

How pruritus affects your dog’s health depends on the degree of the pruritus. Mild pruritus may hardly have any effect at all. However, severe pruritus leads to intense scratching, which may result in painful skin lesions that may become infected. Your dog will often whimper or cry out and may have trouble sleeping.

Every dog has a threshold of pruritus or an “itch threshold.” This is the point where all of the sources of itching finally add up to enough irritation to cause the irresistible urge to scratch. Scratching begins when the stimulation exceeds that threshold. For example, a dog with a mild allergy to house dust mites may be below the threshold but may begin to scratch severely when he becomes infested with fleas.

Pruritus is associated with other skin diseases, including secondary bacterial skin infections (pyoderma) and secondary yeast infections. But it is the main symptom of skin conditions like allergies and skin parasites.

What To Watch For

Scratching or biting. If this continues beyond one day and leads to lesions such as hair loss, reddening of the skin and obvious pain or discomfort, have your dog evaluated by your veterinarian.
Chronic licking of the feet is also a symptom of pruritus.

Diagnosis of Pruritus in Dogs

Diagnostic tests may be needed to determine the cause of the pruritus. Your veterinarian will probably do the following:

A complete and thorough medical history
A thorough physical examination
Skin scrapings to rule out mange mites and other parasites
Fungal cultures of hair to rule out dermatophytes (ringworm)

Treatment of Pruritus in Dogs

The key to relief from pruritus is to identify and treat the underlying cause. Pruritus may be temporarily relieved with medication but the itching often recurs after the medication is finished. Temporary relief may come from the following:

Antihistamines
Fatty acid supplements
Soothing shampoos
Corticosteroids

Home Care

Administer all veterinary prescribed medication as instructed by your veterinarian. Consult with your veterinarian to establish a complete flea control program.

Keep your dog’s coat clean and brushed free of mats.

For more tips – go to Home Care of the Itching Dog.

In-depth Information on Pruritus (Itchiness) in Dogs

Many skin diseases can cause or can contribute to pruritus. Every dog has a threshold of pruritus. When the nerves of the skin are stimulated by mediators of inflammation to a level below that threshold, the dog will not scratch. Scratching begins when the stimulation exceeds that threshold. It is common to see dogs with two or more skin conditions that cause pruritus concurrently. For example, a dog with a mild allergy to house dust mites may be below the threshold but may begin to scratch severely when he becomes infested with fleas.

Allergic Skin Diseases

Flea allergy is the most common allergic skin disease in the United States. Dogs with flea allergy tend to scratch their back ends leading to lesions on the rump, hind legs, tail and belly. Since it takes just one flea to make the dog react, the presence of fleas on the dog may be minimal to absent.
Atopy is a reaction to airborne allergens such as pollens, house dust, house dust mites and molds. Dogs with atopy tend to scratch their ears and face and tend to chew and lick at their feet. The condition is often worse during summer months when pollen and mold levels are increased.
Food allergy is a reaction to one or more ingredients in their food. These dogs tend to scratch in the same places as those with atopy.
Insect allergies (insect bite hypersensitivity) are less common than other allergies. Lesions are evident in areas where insects such as mosquitoes are likely to bite (bridge of nose, ears).
Contact allergy is a reaction to an irritant that touches the skin, often the belly or chest. Allergies of this type are rare.

Parasitic Skin Diseases

Scabies is an intensely pruritic skin condition caused by the sarcoptic mange mite. Lesions are seen on the ears, elbows and hocks (ankles).
Demodectic mange is caused by the demodex mite. This is usually a disease of young dogs and causes dramatic hair loss and dermatitis. This disease is often not pruritic, but can lead to a secondary bacterial infection of the skin (pyoderma) which may be itchy.
Fleas can cause pruritus in dogs that are not flea allergic, although the degree of pruritus is less severe.
Cheyletiellosis is an itchy skin condition caused by the cheyletiella mite. Lesions are usually most dramatic along the top of the back. These mites are sometimes visible to the naked eye as small, moving, white specks, hence the name “walking dandruff mite.”
Lice are small insects that are easily seen with the naked eye that can cause pruritus.
Ear mites cause itching of the ears in dogs and can sometimes cause itching elsewhere on the body.

There are many other causes of pruritus, including secondary bacterial skin infections (pyoderma) and secondary yeast infections.

Diagnosis In-depth of Pruritus in Dogs

The key to treating pruritus is to identify and treat the underlying cause. Your veterinarian may want to perform a few diagnostic tests determine the cause of the pruritus. Tests may include:

A complete medical history. A thorough medical history is the foundation for the diagnosis of any dermatologic condition. The breed of your dog, the age, onset of symptoms, duration of symptoms, severity, season in which the problem occurs and the response to previous medications all are important clues.
A thorough physical examination. A complete general and skin examination that includes the skin, ears, footpads and claws is equally important. Unlike most organ systems in the body, the skin can be directly observed. Therefore, what your veterinarian sees is of value in establishing a diagnosis. Your veterinarian will usually look for primary lesions (those caused directly by the disease) and secondary lesions (those caused by your dog’s response to the disease). The distribution of the lesions on your dog’s body is critical to diagnosis since animals tend to scratch in certain areas with certain diseases. Also, a flea comb is often used to look for fleas, flea dirt or other parasites.
Skin scrapings. Skin scrapings are commonly done to diagnose skin parasites. A scalpel blade is used to scrape layers of skin that are then examined under the microscope for mange mites and other parasites.
Fungal cultures. Your veterinarian may do a culture of the hair to rule out dermatophytes (ringworm). Although not always pruritic, ringworm can sometimes cause animals to scratch and can mimic other skin diseases. A small amount of hair is plucked from a skin lesion, placed on the growth media and incubated for 10 days to four weeks to observe for growth.
Blood and allergy tests. Your veterinarian may elect to do blood tests to assess other organs that may have an effect on the skin, or allergy tests or food trails if allergy is suspected.

Treatment In-depth

Antihistamines. These drugs are much less helpful in dogs than they are in humans and will significantly help only 25 to 30 percent of cases. Nevertheless, they are often prescribed since they are relatively safe drugs when compared to corticosteroids. Some dogs respond better to one antihistamine than another, so veterinarians may try two or three different types before giving up on them.
Fatty acid supplements. These may help relieve pruritus by modulating the immune response and may be helpful for chronic pruritus. Certain fatty acids, such as eicosapentanoic acid found in fish oils, help to change the chemical composition of mediators produced during the allergic response, thereby making them less inflammatory. Like antihistamines, these products are not always helpful but they are relatively safe. Some dogs that do not respond to antihistamines may do well with a combination of antihistamines and fatty acids.
Shampoo therapy. Shampoos that contain colloidal oatmeal are soothing, and because these shampoos are moisturizing, they can be used frequently without drying the skin. Some oatmeal-based shampoos contain topical anesthetics or topical corticosteroids that are safe and further help in reducing pruritus.
Corticosteroids. When other therapies are not effective, corticosteroids such as prednisone may be prescribed. Again, these drugs may help in some cases but are less effective in others. Many side effects associated with corticosteroids restrict their long-term use. Some of these include increased thirst and hunger, which may lead to obesity and suppression of the immune system, which may lead to infections, irritation of the stomach and damage to the liver or adrenal glands. Short-acting, oral corticosteroids are much safer than long-acting injectable, since they can be cleared from the body rapidly should side effects occur.

Follow-up Care of Dogs with Pruritus (Itchiness)

Pruritus can be a frustrating problem because there are many different causes and, therefore, many different treatments. Thus, it is extremely important that you stay in close communication with your veterinarian until the problem is resolved. In addition, you should also do the following:

Administer all medications as instructed.
Keep your dog’s coat clean and properly groomed.
Observe closely for fleas. Flea infestation makes any pruritic problem worse. Consult with your veterinarian to establish a complete flea control program.
Observe for the appearance of new rashes, areas of hair loss or other new lesions that may indicate secondary problems like pyoderma which could require additional medication.