Scientists have found seven genes linked to the development of the ailment, which could lead to new treatments.
Researchers from Imperial College London and colleagues around the world carried out more than half-a-million genetic tests on 26,000 subjects.
The findings, published in the ‘New England Journal of Medicine’, suggest that allergies are a consequence of asthma, which causes damaged airways.
They also discovered that adult-onset asthma and childhood asthma were different diseases.
David Strachan, professor of epidemiology at St George’s University of London, who co-authored the study into the condition, said: “Asthma has often been considered a single disease.