Dog flea shampoos are specifically formulated for the pH balance and skin sensitivity of dogs, and may contain ingredients that are harmful or irritating to horses. Some shampoos may contain harsh chemicals and fragrances, which can cause skin irritation and other health issues.
Horses have a more sensitive skin and are more prone to skin allergies, so using a dog flea shampoo can increase the risk of adverse reactions such as skin rashes, itching, and inflammation.
Additionally, dog flea shampoos may not be effective in treating fleas on horses, as fleas that infest horses are a different species than those that infest dogs.
Therefore, it is always best to use horse-specific flea and tick shampoos or consult with a veterinarian before using any dog products on your horse.