I don't like usin flea shampoos on the dogs unless there's a bad case of fleas in the house. Mine have such sensitive skin. I only use oatmeal shampoo and bathe about once a month. I've had to use baby lotion on my boy after flea shampoo cuz he dried up and flakes so bad... An allergic reaction would be more like redness, blotches, hives, swelling, excessive scratching, etc. Just sounds like too harsh of shampoo on sensitive skin.