here's a link that nina posted (dibby dog). anywho, it has a chart with conditions, descriptions, etc of skin ailments in dogs.
http://www.lowchensaustralia.com/health/skin.htmit says:
Condition:
Allergic and Irritant
Contact Dermatitis
Description:
Reaction of the pet's skin to something it had contact with such as wool or plastics
Symptoms:
Red skin and small bumps or blisters on the areas of skin that are sparsely haired and directly exposed to the offending substance, itching
Diagnosis:
Patch test, exclusion trials
Treatment:
Restrict exposure to the allergen or contact irritant in the pet's environment, steroids, antihistamines
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Bacterial Infection
Often occurs as a result of another condition
Redness, pustules, bumps, sometimes itching
Microscopic examination of smear; culture
Treat underlying condition; topical and/or oral antibiotics
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Chiggers (Harvest mites)
Seasonal disease caused by larvae of the chigger
Itching, bumps usually on feet, abdomen, folds at base of ears
Visualization of mite larvae or microscopic examination of skin scraping
Permethrin (Dogs ONLY) or Pyrethrin