The role of topical therapy in the successful treatment of allergic dermatitis


The role of topical therapy in the successful treatment of allergic dermatitis

Jun 01, 2006

Topical therapy is an important—and in many cases essential—component of successfully managing allergic dermatitis in dogs. When used as an adjunctive treatment for generalized disease, topical therapy often minimizes dependence on systemic medications that may be deleterious to the patient's health. In addition, topical therapy may be more effective in treating localized or regionalized pruritus.

The development of new products with improved active ingredients and delivery systems has made topical therapy even more effective. The same active ingredients are often used in different delivery systems, such as shampoos, rinses, powders, lotions, sprays, creams, emulsions, ointments, and gels. The advantages and disadvantages of these formulations vary, as do their cost, ease of application, and efficacy.

Shampoos and leave-on products

Shampoo therapy is the cornerstone of the successful topical management of an allergic patient. Frequent bathing with the correct product helps control pruritus by removing offending allergens and desensitizing and moisturizing the skin. Critical factors affecting the efficacy of shampoo therapy include client compliance, contact time, frequency of use, and active ingredients.

Client compliance is the most important component of successful shampoo therapy. Practitioners should train themselves and their technicians to educate clients about contact time and frequency of use to increase the success rate for allergic patients. Practitioners must stress that effective shampoo therapy requires a minimum of 10 contact minutes before rinsing to allow sufficient product interaction with the skin. Remember that the longest 10 minutes of a dog owner's life are the 10 minutes spent lathering his dog in a bathtub!

Table 1. Topical Antipruritic Ingredients and Products
It's also important to discuss frequency of shampoo therapy with owners. Although frequency generally depends on the specific condition, shampooing once or twice weekly is usually necessary to successfully manage a pruritic patient. When practitioners educate clients about why frequency of use and contact time are essential, compliance increases.

In addition to shampoos, products that are left on the skin, such as lotions, creams, and sprays, may provide added advantages. These products can often be used in conjunction with appropriate shampoo therapy. Most of the active ingredients in shampoos are also available in these leave-on formulations. The main disadvantage of using these products is that they require direct skin contact. Therefore, they are more beneficial in short-coated dogs or in areas where the hair can be clipped or parted easily, such as the paws, axillae, inguina, and ventral abdomen.

Active ingredients

Practitioners should familiarize themselves with several important ingredients of antipruritic products (see Table 1 for products containing these ingredients):

Colloidal oatmeal, fatty acids, urea, glycerin, and other moisturizers help alleviate skin dryness through humectant properties. This subsequently allows for an increase in the pruritic threshold of the skin.

Menthol, camphor, and thymol act by substituting other sensations for the pruritus. A cooling sensation helps decrease pruritus and may also help increase the pruritic threshold.

Pramoxine , a local anesthetic for skin nerve endings, may also have antipruritic properties that have not yet been completely determined.1 Studies have shown that pramoxine is safer than other topical anesthetics.1

Lidocaine is another local anesthetic that affects peripheral nerves and can be used safely in topical products.

Diphenhydramine , an antihistamine, can have mild antipruritic effects when administered topically. It has been shown to cross the epidermal barrier to exert its antihistaminic effects.1