Environmental medicine explores the role of dietary and environmental allergens in certain health conditions, analyzing the chemical and physical hazards in the four major environmental elements: air, water, soil and food. Factors such as dust, molds, chemicals, and certain foods may trigger allergic reactions that can radically influence diseases ranging from asthma and hay fever to headaches and depression. Protocols include the prevention of ill-health from effects from environmental exposures. Environmental Medicine is also termed Clinical Ecology.