- Pollen from trees, grass, and weeds
- Mold
- Dust mites
- Insect bites
- Wool and carpet fibers
- Certain foods
- Medications
- Other animals
- Skin disease – Skin disease is the most common symptom an allergic pet can exhibit. When affected by a certain allergen, pets’ skin can become red, itchy, and scaly. This skin irritation can be widespread or confined to concentrated areas like the face, belly, feet, groin, and hindquarters.