To differentiate between a rash caused by poison ivy, oak, or sumac and other skin irritations in pets, observe the rash's appearance and the pet's recent activities. Rashes from these plants typically present as red, bumpy, and may form blisters if severe. They usually appear on areas of less fur coverage, such as the belly or face. Consider whether the pet has been in areas likely to have these plants. Other irritations might be more spread out, less defined, or associated with changes in diet or new products.