A. the two most common reasons for this symptom are fleas infestation and allergies. Make sure to use a good quality flea treatment every month (ex. Revolution, advantage, advocate, comfortis, frontline), even if you don't see fleas sometimes a flea or two is enough to cause a reaction like the one you are describing. If the treatment doesn't help, good chances that you are dealing with an allergic reaction. That could be related to food, something in the house or something outside. It's usually difficult to find the cause of the allergy right away. If the symptoms get worst take him to the vet, he will prescribe some meds to stop the itchiness and might also add some antibiotic treatment.
A. That may be use to a skin allergy and most commonly is a flea allergy dermatitis. I would suggest to treat correctly for fleas and potentially (and use vet prescription) give him a low dosage of steroids to keep the other under control. A buster collar (cone) could help as well to stop the autotraumatism and allow the skin to settle down.
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