Mast cells and other airway cells are sensitized and become activated when they encounter specific antigens. In children with wheezing during a viral infection, allergy or a family history of allergy is the strongest associated factor with recurrent asthma throughout childhood. Although asthma occurs most commonly in children, it can also occur later in life. Adult-onset asthma can be associated with atopy. However, there can be also other causes of asthma.
Some adults develop asthma without IgE antibodies to allergens.
Occupational exposures to materials like plastic resins, biological enzymes, animal products and wood dusts can also cause asthma. In making the diagnosis of asthma the clinician should look for a history of episodic airflow obstruction which is at least partially reversible. Alternative diagnoses should always be excluded. The physician should look for a history of wheezing, recurrent cough, particularly worse at night, recurrent shortness of breath, or recurrent chest tightness. These symptoms may occur or worsen with exercise, viral infection, animals, smoke, pollen, mold, strong emotional expression, menses, and airborne chemicals or dust.