You really need to take Chloe to your vet and make sure you aren't dealing with a staph infection, mites, etc.
Johnson's Baby shampoo is too harsh. It was developed to remove cradle cap in infants. That could have contributed to the problem.
Inhaled allergies are much more common that food allergies. Are you using a detergent with perfumes and dyes for her bedding? That can cause an allergic reaction. Even carpet fibers can cause an allergic reaction.
Adding fatty acids from fish oil can help boost the immune system.
Omega Fatty Acids: Sources, Effects, and Therapeutic Usesin Dogs
Chloe may need an antihistamine like Benedryl or Zyrtec to help with her itching, but check with your vet first.