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Pruritis Alopecia Allergies Lumps and Bumps


In order to best appreciate the types and nature of the skin anomalies to be discussed, a link is available to information on the general structure of skin, including the layers and cellular organization, the various glands, hair and follicles . Keep in mind that there are specialized regions of skin, such as foot pads and nose that, although generally similar in structure to true skin, have somewhat different characteristics.
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Pruritis

What is pruritis? It is the unpleasant sensation ("itch") that provokes a desire to scratch. You may wonder, "Of what benefit is itching and the response to it, i.e. scratching"?

That is a good question...and I can not provide an answer to it. I can only say that it happens and that it is the most common symptom in veterinary dermatology. This section will describe the process, and the conditions that stimulate it. By understanding pruritis, you will, hopefully, appreciate the way we try to deal with it within veterinary medicine.

Pruritis Basics: (Mechanisms)
The skin contains a vast network of nerve fibers of various types that deal with sensation, such as pruritis, pain, temperature and touch. The exact type of nerves that result in pruritis, and their association with other portions of the nervous system is poorly appreciated at this time. However, suffice it to say that the activities of these nerves are stimulated by chemical mediators (derived from undesirable immune system reactions to allergens), some of which are present in the membranes of skin cells and other cell types that are found in close association in the skin. Suggested mediator types are proteolytic (protein-degrading)enzymes (from microorganisms and from other cell types), prostaglandins and leukotrienes; the latter two are derived from the breakdown of cell membrane via pathways involving arachadonic acid cyclooxygenase and lipooxygenase (these are often sites at which medication to inhibit pruritis are targeted). Modulation of sensory input (worsening of itch intensity) from other factors...,humidity (dry skin is often itchier than moist skin) boredom, pain, temperature and touch can and do occur, though mechanism(s) are not understood.

Treatment of Pruritis
Priniples:
· Pharmacological Intervention

1. Topicals
2. Systemic
    1. Remember, histamine was one of the mediators listed for pruritis; antihistamines prevent the release of histamine from the stimulated source cells or the binding of histamine to a site that, in turn results in the release of histamine. Hence anti-histamines work best before the histamine release has been triggered (i.e as a preventative)
    2. There are many different antihistamine products...some may work better than others in some animals. Sometimes more than one must be tried for several weeks before going to another
    3. Antihistamines are often used in conjunction with other antipruritics
    4. Some tricyclic antidepressant medications, such as doxepin, contain potent antihistamine activivity and are occasionally useful in the control of itch
Lumps & Bumps
Lumps and bumps are smooth or irregular, raised, flat or depressed, soft or firm discrete areas within or just beneath the skin. The link, descriptions and definitions describes some of these. These include papules, pustules, vesicles, comedones, cysts, nevi, keratoses, horn, tumors/neoplasia , abcesses, granulomas, warts, ulcers, and excoriations. Each of these can be further subdivided into specific type, whether benign or malignant including grade of malignancy, histological appearance, and cause. This page will discuss selected examples...ones that you are most likely to experience with your pet.

Allergies

Allergies (hypersensitivities) represent undesirable (from comfort point of view ) responses by the immune system to substances present in the environment, including components of food. The mechanism(s) is complex, involving the interaction of immune molecules with allergic stimulant (the "antigen") with subsequent release of inflammatory-active chemical mediators which, for the purpose of this discussion, are manifest as redness, pruritis, hair loss and seborrhea. The offending antigen is usually something the animal has previously been exposed to..e.g. something in the diet, something in the environment. Allergy to environmental antigens is known as "Atopy". Diagnosis of atopy requires first eliminating other causes of the clinical signs, then once the diagnosis is made, then further tests are performed to elucidate the causative allergens

Alopecia

These are stylized examples only......

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