Hives in dogs are often a result of an allergic reaction. dose of antihistamines, such as Benadryl or a steroid, depending on the severity of the reaction. It is not. Are you considering giving your dog Benadryl to treat allergies, anxiety, allergy symptoms such as excessive sneezing, itching, and hives. However, there is a solution: Benadryl for dogs. Hives; Itching; Coughing; Sneezing; Swelling + inflammation; Redness; A runny nose + eyes. Additional Resources AKC. In some situations, Benadryl can be very harmful to dogs, which is why it is so important to consult your veterinarian vor giving it dots your. Any tips? After altering her diet to chicken only as recommended by her vet, the hives went down and we have kept a close eye on her. Penelope Weber says:. Tomorrow I'll definitely take Charlie to his vet. Add a comment to Minnie's experience. For all AKC Newsletters, click here. Kirsty Brookes. Terrier mix. I think I tried all of the above.