Section: Overview
Diagnosis
The medical history is very important when trying to establish a diagnosis in animals with skin conditions. You will be asked to describe all medications, chemicals, shampoos, and dips that you have used on your dog. Timing also is important when trying to determine the offending substance. It is important to be very thorough when providing information about carpet cleaning, deodorizers, and chemicals applied inside and outside of your house. If the reaction is allergic in nature, products that have been used for a long time cannot be ruled out because of the requirement for a previous sensitization period.
The usual medical approach to an animal with a skin condition proceeds by steps. Thus, your veterinarian will rule out more common diseases before considering a less common disorder such as contact dermatitis. Skin scrapings to rule out demodectic and sarcoptic mange, fungal culture for dermatophytes (ringworm) and antibiotic therapy for possible bacterial skin infection may be necessary.
Diagnosis of contact dermatitis is made by observing resolution of clinical signs after withdrawal of the presumed offending substance and relapse of clinical signs with re-exposure.
Patch testing also may be used to screen suspected chemicals or plants. An area on the lateral chest wall is clipped 24 hours before patch testing.
Samples of various suspected chemicals and plants are applied directly to the skin and bandaged into place to insure prolonged contact with the skin.
After 48 hours, the bandage is removed and the skin examined for reactions. Signs of a positive reaction include erythema (redness), small papules (red bumps) or vesicles (blisters).
Treatment
The treatment is to remove the dog from the offending substance.
If contact allergy is suspected, you may asked to confine your animal to a limited area of his normal environment to prevent contact with suspected substances. Confinement should start after a thorough bath, because small particles of the substance may remain on the skin and perpetuate clinical signs.
Compliance is very important. If plants are suspected, you may have to use specialized boots and T-shirts to protect your dog's skin and walk the animal only on concrete areas until the lesions have healed, typically 10 to 14 days.
Bacterial skin infections occur commonly in dogs with contact allergy or irritant reactions. You may be asked to administer an antibiotic for a minimum of three to four weeks.
In severe cases, a course of anti-inflammatory medications such as prednisone may be necessary to make your pet more comfortable. Orally administered medications usually are safer than injectable preparations and should be used as a first choice. Adverse effects of this type of therapy include increased appetite, increased thirst and increased urinations. Avoidance of the offending allergen should be attempted whenever possible, because corticosteroids tend to lose their efficacy with repeated use. This is called tachyphylaxis.
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