Topical therapies can offer relief for some skin conditions

Apr 01, 2003

Photo 1: A 2-year-old Coonhound with severe pruritus, odor, and hair loss with hyperpigmentation and lichenification on face and neck.
In my practice, I receive numerous phone calls for consultations concerning the choice of shampoo or specific topical spray/lotion to treat skin disease. It can be very difficult to choose the right topical product. But with a few tips, a few rules to follow and some insight into shampoo ingredients, you'll be well on your way.

Variety of skin types Normal skin: Normal skin should be relatively smooth and range in color from pink to black. Some dogs develop blackening (hyperpigmentation) of the skin and could be a normal finding over time. The skin secretes oil and sweat but should not be greasy or oily. A few exfoliated cells can be found (sometimes confused as pathology called seborrhea) but should be difficult to find and not adhered to the skin or hair shafts.

Normal skin should not be thickened (lichenification) unless it is in an area of trauma or pressure. Normal pressure point calluses occur in areas of trauma over boney prominences such as the elbows, lateral tarsi, and points of the hips. Some breeds such as bull terriers can develop large pressure points over odd places such as the dorsal bridge of the nose.

Photo 2: An 8-year-old Newfoundland with epidermal collarettes and alopecia on trunk.
Some areas can have increase moisture or exudation (oil) under normal conditions and can include skin fold areas, lip folds, vulvar folds and ear canals. These areas trap moisture, and unless pruritus, alopecia, erythema, or odor and discharge are evident may be a normal finding.

Abnormal skin: Skin that is diseased, infected, or traumatized can display evidence that something is not "normal". Increased amounts of exudation can occur (mainly oil from sebaceous gland origin) and produce an oily or waxy feeling. This can act as a "culture medium" and microbial colonization with either staphylococcus or Malassezia (yeast) can occur. Bacterial or yeast overgrowth can also result from other causes including increased moisture from licking/self-trauma or simply from uncontrolled allergy. Increased exfoliation (seborrhea) can be very obvious and be the result of a primary defect in cornification (epidermal skin cell turn-over) or secondary to allergy.

Photo 3: A 4-year-old West Highland White Terrier with very pruritic limbs and feet and numerous papules, pustules, and crusts on groin and rear limbs.
These extra skin cells can harbor microbes readily. Staphylococcus and Malassezia like to "cling" to these surface skin cells and cause disease. Serum oozing from the skin from self-trauma or severe inflammation can cause crusts. Crusts can be pruritic and futher perpeturate the itch/scratch cycle. Crusts can also be formed from dried pus from bacterial infection.

Rules of topical therapy

1. Choice of topical therapy hopefully is based on specific diagnosis. 2.Use the least number of preparations. 3. Familiarize yourself with the ingredients. 4. Use the mildest form. 5. Keep client educated and informed.

Goals of topical therapy:

1. Remove or control abnormal debris on skin. 2. Cure infectious or parasitic disease. 3. Control allergic symptoms. 4. Ultimately provide maintenance therapy if needed.

Photo 4: A 6-month-old Norfolk Terrrier with numerous scales on entire body. Scales are most evident on groin.
Topical medication formulations In most topical medications, the product contains the active ingredient(s) and some form of a vehicle. Active ingredients are our main focus when selecting a topical product for a specific dermatologic condition. However, some vehicles can also be beneficial for the treatment and even act synergistically with the active ingredient. The choice of the active ingredient(s) is based upon the disease(s) present and the desired effect.

Choosing the vehicle is not easily done due to the limited products available to us and the limited types of vehicles used in the topical preparation. Vehicles include alcohols and propylene glycol for example. Also, the vehicle (usually inert in this instance) may facilitate absorption of the active ingredients.

Rules for vehicle choice:

1. Acute lesions: Allow exudation to "flow", encourage drainage, and dry the area being treated. ("If its wet, dry it.") 2. Chronic lesions: Rehydrate skin. ("If its dry, wet it")

Active Ingredients

1. Corticosteroids: Supress inflammation (mainly used in the absence of infection). It is used to control pruritus and inflammation. Problems that arise with usage can include thinning of skin with chronic use of higher potency corticosteroids and supressing the adrenal-cortical axis.

2. Antibiotics: Kill bacteria. Antibiotics are very useful in cases of pyoderma. Problems can include contact dermatitis (neomycin). Antibacterials include neomycin/gentomycin, mupirocin, sulfur, benzoyl peroxide, ethyl lactate, chlorhexidine, and acetic acid.