- Common Disease Name:
- Itchy Skin
- Medical Term for Disease:
- Pruritis is a symptom rather than a disease. Pruritis is the sensation that provokes the desire to scratch, rub, chew or lick. It usually indicates the skin is inflamed. Abnormal nerve sensations can cause pruritis as well.
- Species Affected by Disease:
- Dogs
- Age Animal Usually Affected:
- Any
- Commonly Affected Breeds:
- Any
- Sex Usually Affected:
- Any
- Disease Symptoms:
- Excessive licking, chewing, or scratching
- Method(s) of Diagnosis:
- Severe itching that keeps the patient and owner awake is suggestive of
flea allergy/infestation, mites or scabies, food allergy, or a skin yeast infection. Atopy or environmental allergies causing skin itching is usually very steroid-responsive and show up seasonally, but an progress to non-seasonal.
Itching is usually on the face, feet, ears, forelimbs, under the forelegs and chest, flanks and also the rump. Flea allergic and food allergic dogs are often getting atopy as well, and may show similar signs. Skin scrapes, cytology and fungal cultures with microscopic identification are very useful in identifying either primary or coexisting diseases caused by parasites or other microorganisms. Trial treatment is often diagnostic in with hypoallergenic dietary trial or scabicidal treatment as canine scabies can be difficult to diagnose and skin scrapes are often negative. Skin testing for environmental allergies (atopy) is in two different methods: intradermal skin testing or RAST testing where blood is drawn and serum is tested for allergies. A skin biopsy is useful when the lesions associated with pruritus are unusual and an immune- mediated disease is expected or the history and physical findings do not match. - Disease Causes:
- Usually there is pruritis because the skin is inflamed. Hair loss without itching can be an endocrine problem. Causes include parasites such as fleas, ticks, scabies, demodex, ear mites, lice, or other parasite migration through the skin. Allergies can cause itching such as flea bite hypersensitivity, food allergy, contact allergy, inhalant or atopic allergy, drug allergy or a sensitivity to bacteria on the skin, such as staph hypersensitivity or fungal allergy. Also causing pruritis can be seborrhea, skin cancer, hair follicle tumors, immune and endocrine disease and others.
- Treatment:
- Topical therapy is helpful in mildly itchy pets. For localized areas, sprays, lotions and creams are most appropriate. If the itching involves many areas, shampoos are the preferred means of application. Colloidal oatmeal can be found in virtually all forms of topical therapy. In some cases, it is very beneficial, but its duration of effect is usually less than two days. Topical antihistamines may be found alone or in combination with other ingredients. They have not been shown to have a beneficial effect. Topical anesthetics may offer only a very short duration of effect.
Antibacterial shampoos help control bacterial infections that cause itching. However, some antibacterial shampoos such as those containing benzyl peroxide or iodine can cause increased itching. Lime sulfur (which has a bad odor and can stain) can be antipruritic while also having antiparisitic, antibacterial, and antifungal properties. Topical steroids are probably the most useful topical medication, but there is risks involved. Cool water is often soothing. It helps to think of the three separate and individual pathways that lead to inflammation and itching. Steroids block all three pathways, but because of their side effects, drugs that help block the individual pathways should be considered.
• Antihistamines, which include drugs such as hydroxyzine, diphenhydramine, and chlorpheniramine, block only one of the three main pathways that lead to inflammation and itching.
• Fatty acids are available in powder, liquid, and capsules. They help block individual pathways that lead to inflammation, but may require 6-8 weeks of use until maximum
effect is observed. Fatty acids work better as a preventative rather than stopping the inflammation once it has become a problem. They also help control dry or flaky skin which can also cause itching. Many different brand names of this type of drug are available.
• Drugs with psychogenic actions can also be helpful in controlling itch. Amitriptyline (Elevil¨), a drug used as an antidepressant in humans, has rather potent antihistaminic actions in dogs and can be as beneficial as antihistamines in treating allergy induced itching. Side effects are similar to antihistamines. Flyoxetine (Prozac¨) has been used successfully in treating only some dogs with ""lick granuloma"" or acral lick dermatitis. Diazepam (Valium¨) has also been beneficial in a few cases. However, recent reports of acute hepatotoxicity in cats should be taken into account.
• The use of drugs other than steroids to control itching is less convenient, but reduces the potential for serious side effects. If these other drugs are not totally effective in controlling clinical signs, they often help reduce the amount of steroids that are necessary to decrease itching. - Prognosis:
- Steroids are the most well-known drug used to control itching but have significant long-term and not always obvious side effects. To help decrease side effects with long term use, daily administration of oral corticosteroids (including prednisone or methylprednisone) should be avoided. Steroids, used wisely, are usually safe. Short term use seldom causes serious problems. They should be avoided in cases with a history of pancreatitis, diabetes mellitus, calcinosis cutis, demodicosis, dermatophytois and other infectious diseases. Due to the chronic nature of pruritus, client frustration is common. For example, demodicosis, dermatophytosis, pyoderma, endocrine disease, or food allergy may occur spontaneously in a patient who has been suffering from a single disease such as inhalant allergies. Skin scrapes and other tests may have been negative or normal during the original workup, but that does not imply that they will remain undiagnostic. Complications are also common with chronic steroid use. In some cases, the application of anything topically, including water and products containing alcohol, iodine, and benzyl peroxide, can exacerbate pruritus. Cool water may be soothing. Steroids should be avoided in cases of pruritus caused by an infectious etiology.
- Complications:
- If the dog scratches enough to tear the skin, wound infections are possible.
- Prevention:
- Prevent flea infestation, keep dog clean, supplement diet with fish oils.
