An estimated 25 million Americans have asthma, a chronic illness of the respiratory system that involves inflammation and constriction of airways, as well as increased mucus production. Asthma is usually the result of hypersensitivity to certain triggers such as allergens, air temperature fluctuations, exercise, or stress.

Individuals suffering from asthma usually experience breathlessness, tightness in the chest, and wheezing during symptomatic episodes. Coughing may occur at night or in the early morning. All these symptoms are the result of constricted airflow and respiratory inflammation and can be treated. Allergens like pollen can cause the body to release large amounts of histamine, exacerbating asthma by increasing mucus production in the lungs and creating inflammatory responses in the lung tissue

Histamines can also cause muscle contractions in the small branches of the lungs, resulting in wheezing and tightness in the chest.