The disease is a genetic and environmental interaction caused by the multi-factor disease, risk factors may exist in all age groups.
Patients with atopic physique, usually showing family clustering.
2. allergen exposure
An allergen is an antigen that induces a specific IgE antibody and reacts with it. They are mostly derived from animals, plants, insects, fungi or occupational substances. Its composition is protein or glycoprotein, a very small number of polysaccharides. The allergen is divided into inhalation allergen and food allergen. Inhalation allergens are the main cause.