Early asthma can start 1-2 hours after exposure. The child could complain of tightness or shortness of breath. Usually a child can be treated with his theophylline inhaler. Later stages can include inflammation of the lungs and can last 12-24 hours. Constant allergic events contribute to developments of bronchial hyperactivity.
Airways can remain sensitive for days, weeks or even months at a time.
Certain stimulants like exercise cause only temporary changes and do not make the bronchioles hypersensitive but other triggers like allergens and infections can affect lung activity for months Stopping lung inflammation reduces this hypersensitivity. This is usually accomplished with medication. It won't happen overnight. You and your child will have to recognize their triggers. Triggers are the things which will start an asthma problem.