Pets can eat, drink and sleep with the collar on. After an initial 1-2 hour period of strange behavior most pets accept the collar without further concern. The plastic collar can be cleaned by wiping it with a wet cloth. Rubbing alcohol can be used for tougher stains. The collar can be removed for cleaning but otherwise should be left on the pet at all times. Taking it off and putting it on repeatedly just makes it harder for the pet to adjust to the collar.
After the problem has resolved do not throw the collar away. Keep it for future use. Pets routinely develop problems where excessive licking aggravates the condition. Skin rashes can often be successfully treated at home with skin ointments and putting the collar on the pet for a few days. This can often save you a trip to the doctor, something both you and your pet would appreciate.