Cause: Fleas, ticks, mites (which cause mange) used to be the bane of the pet and pet owner, especially here in the south where these things multiply so fast that they re-appear one day after dipping (bathing) with pestacide.
Appearance: I won't use this space to describe these tiny bugs, but you may see tiny black flea excrement or an engorged tick in your dog's coat. Dogs will scratch readily at these biting pests. A large infestation will literally drain the life out of a puppy.
Treatment: Blessedly, the new topical products: Frontline, Frontline Plus, Advantage, Revolution have created alot of peace for dogs and their owners. In my experience, each of these products works almost 100% on fleas and only marginally on ticks. All need re-application every month for stubborn ticks. Read the package inserts. The insecticide most commonly used in commercial flea-tick shampoos and dips is Pyrethrin (see each label as concentrations vary). I've also used a tick-collar called "Preventic" which is said to work for three months, but I can't say for sure how effective it was, as I also called an exterminator that time. For a bad tick infestation, such as is common in the South, you will have to call a professional exterminator for repeat insecticide treatments to your yard and home (and/or kennel). Tell them what pests you are trying to kill. (In my area, professional extermination is well worth the price vs exposure to dangerous chemicals). Revolution, the newest, also claims success on mites. For the horribly pruritic red sarcoptic mange, a human prescription cream, "Elimite" (permethrin 5%) is also effective.