The document discusses the development and causes of asthma. It outlines several factors that can contribute to the development of asthma, including genetic factors, exposure to cigarette smoke in utero or as a child, low birth weight, food or drug allergies, lifestyle, and childhood lung infections. Common asthma triggers include dust mites, mold, cigarette smoke, pollution, pets, pollen, stress, food preservatives, cleaning products, chest infections, and emotions. Triggers can vary between individuals. The total allergen load, or threshold of allergen exposure, can also trigger an asthma attack.