Environmental allergens are a major trigger of asthma, but not all asthmatics are allergic, of course.
This study from Connecticut, USA included 300 children with allergic and non-allergic asthma, based on allergy skin tests.
Two-thirds of the asthmatic children had at least one positive skin test. These allergic patients were more likely to have a history of eczema.
The number of positive skin tests and specific sensitivities did not correlate with age of onset of asthma or asthma severity.
There was no difference between allergic patients and non-allergic patients in terms of family history of atopy or asthma, age of onset of asthma, gender, or asthma severity.
There were no clinical features that could distinguish allergic from non-allergic asthma. All children with asthma should undergo allergy testing in order to identify allergic triggers and to avoid the institution of unnecessary environmental control measures in non-allergic patients.