Allergens are known to cause allergic reactions and respiratory diseases to sensitive people. Seasonal allergic reactions can be caused by indoor allergens and manifests as nasal congestion, runny nose, watering of the eyes, sneezing, and postnasal drip. Symptoms of asthma, including wheezing or difficulty breathing, can also occur in susceptible individuals. Allergic reaction to indoor allergens can also cause conjunctivitis, an inflammation of the lining membranes of the eyes. Symptoms of this condition include red, watery, and itching eyes. Allergic symptoms involving the skin include eczema, or allergic dermatitis, characterized by a skin rash associated with itching. This usually results from direct contact with the allergen.