The most common cause of these crazy skin problems is allergies, especially with this breed. These allergies could be from grass, contact with a cleaner or chemical or could even be food related. IIt might be the shampoo that you used. The allergy part is sometimes tough to treat but there are some simple things that you can do.
- Talk with your vet about a low allergy diet. Rabbit and potato is my favorite and my dogs do well on it.
- Get the dog started on frontline to eliminate the chance that this is a flea allergy. If he's already on it, keep in mind that it only takes ONE flea to get the cycle started if the dog is allergic to fleas.
- Use a prescribed dose of benadryl when this gets bad. My vet recommends 1 mg per lb of dog given every 8-12 hours as needed when the itching starts
When the dog abrades the skin by chewing and scratching, this opens up the body to infection. Many dogs need antibiotics because of this.
See the vet so that they can get the dog started on an antibiotic if you suspect this.
Many dogs also need a shot of prednisone to control the itch and give the skin time to heal.
Keep in mind that you thyroid conditions can also cause hair loss and skin issues so you will want to have this checked if the suggestions above do not help.
I hope this helps!
Let me know if you still have questions.