A reversible narrowing of the large and small airways due to spasm of the bronchial smooth muscle, inflammation of the bronchial mucosa, and production of mucus.  Asthmatic attacks are brought on by stress, exercise, viral respiratory infections, and allergens such as pollen, mold, dust and animal danders.  One study showed a decrease in Bronchiodialator use by 20% with chiropractic care, and decreased the severity of the reactions by 39%.  Even better, after a year follow up, the improvements maintained.

References:
Bronfort, G: Chronic pediatric asthma and chiropractic spinal manipulation: a prospective clinical series and randomized clinical pilot study, JMPT 2001; 24: 369-77