While cat shampoo can be used on dogs in emergencies, it's not ideal for regular use due to differences in skin pH levels and coat structures between cats and dogs. Dogs have a skin pH ranging from 6.2 to 7.5, whereas cats have a pH around 5.5, making cat shampoos potentially less effective and possibly irritating for dogs. It's recommended to use shampoos specifically formulated for dogs to ensure their skin and coat remain healthy.