Hay fever, also called pollen allergy, is a common allergic disease causing rhinitis and conjunctivitis on exposure to an allergen. The prototype is allergy to grasses, but pollens of many trees, weeds, and grasses (e.g., ragweed, Timothy grass) may provoke seasonal hay fever in sensitized individuals. Allergy to fungi or to the house dust mite may lead to perennial rhinitis; animal fur or feathers may also provoke attacks. Susceptibility is often associated with asthma, eczema, and aspirin sensitivity in the individual or his or her family. Treatment consists of allergen avoidance, desensitizing injections, and cromoglycate, antihistamines, or steroid sprays in difficult cases.