Exposure to cigarette smoke can increase the risk of respiratory infections, asthma, bronchitis, and sinusitis. Chemical additives and fragrances in soaps are common causes of skin allergies rather than the cleaning chemicals. Pollen from wind-pollinated plants like trees and grasses are a major cause of airborne allergies due to their small, lightweight particles. Sulfites used as preservatives in some foods can cause mild to severe allergic reactions in sensitive individuals. Contact with the oil from poison ivy, oak, or sumac plants can cause a skin rash, and inhalation can also cause respiratory irritation. The article provides information on common indoor and outdoor allergens and symptoms.