Skin allergies can be caused by internal factors such as congenital allergies, or external factors such as pollen, animal hair and other external allergens entering the body, resulting in allergies. 1. Congenital allergy: related to genetic factors, easily stimulated by external factors leading to skin allergies. 2. Allergen stimulation: the skin barrier is damaged, stimulated by allergens (food: peanuts, soybeans, milk, eggs, etc.; inhalants: pollen, dust mites, etc.; contact: animal hair, etc.; drugs: penicillin, sulfa, etc.) leading to the body’s immune activity abnormalities to form an allergic reaction. If you have recurring allergies, it is recommended that you go to the hospital for an allergen test to determine the cause of the allergy and then give targeted treatment.