Soap left in the coat after the bath is a leading culprit along with flea infestations, wounds, allergies and hormone disorders. If your Chow breaks out shortly after a bath, you can suspect you didn't rinse him well enough. Another bath with a more thorough rinsing will be necessary. A Chow that's allergic to fleas will fly into a coat-chewing frenzy over just one flea bite. Minor skin irritations and insect bites are high on the hot spot list, too.
Allergies usually appear after puppyhood and are more prevalent in the summer months.
Hormone disorders like thyroid deficiency also usually appear after puppyhood. These are year-round conditions. The key to controlling and clearing up a hot spot is to relieve the itching and restraining the Chow from chewing on himself. Medication applied to the skin is very helpful. There are several ointments you can get by presciption from your veterinarian such as Panalog and Gentocin ointment and Variton cream.