How does hypersensitivity trigger in asthmatic patient

Generally, asthma falls into 2 broad groups: extrinsic asthma with evidence of Allergy (hypersentivity to external allergens) & intrinstic asthma with no known allergic cause.

Extrinsic asthma usually occurs in atopic children i.e. those who have allergic tendencies. These children often suffer from other allergic disorders such as infantile eczema, allergic rhinitis, skin allergy, hay fever, food allergy or sensitivity to drugs. There is often a similar history of these disorders in other members of the family though the number of asthmatic childern without family history of atopy are on the increse in recent years.