http://www.scuba-doc.com/asthma.htm
1). Exercise or cold induced asthmatics should not dive.(BS-AC adds 'emotional attacks')
2). Asthmatics requiring 'rescue or reliever' medication should not dive. Asthmatics on chronic maintenance bronchodilation ('controller') and inhaled steroids are thought to be able to dive. Recommendations vary, however, and the BS-AC recommends that asthmatics should not dive if he/she has needed a therapeutic bronchodilator in the last 48 hours or has had any other chest symptoms.They feel that the asthmatic should not need more than occasional bronchodilators, i.e. daily usage would be a disqualifying factor, but inhaled steroids/cromoglycate/nedocromil are permissible.
3). Mild to moderate asthmatics with normal screening spirometry can be considered candidates for diving. (FEV1/FVC ratio above 85% of predicted)
4). If an asthmatic has an attack, screening spirometry should be done and the individual should not dive until his airway function returns to normal.
---Asthmatics may dive if they have allergic asthma but not if they have cold, exercise or emotion induced asthma.
---All asthmatics should be managed in accordance with British Thoracic Society Guidelines.
---Only well-controlled asthmatics may dive.
---Asthmatics should not dive if he/she has needed a therapeutic bronchodilator in the last 48 hours or has had any other chest symptoms.