Allergens of eczema are divided into endogenous and exogenous allergens. Endogenous allergens are internal factors, such as abnormal immune function and intrinsic diseases, such as inflammatory diarrhea of the intestine, damage to the intestinal mucosal barrier, absorption of some macromolecules that can easily cause allergies, as well as endocrine diseases nutritional disorders, abnormal visceral function, tumors, etc. may trigger or aggravate eczema. Hereditary or acquired skin structural abnormalities and functional defects, such as natural dry skin and poor barrier function, may also cause eczema. Exogenous allergens, such as allergies to substances in the environment or skin irritation from environmental factors, changes in ambient temperature and humidity, and sun exposure, can aggravate eczema. Microorganisms can aggravate eczema by direct invasion or by inducing an immune response, such as stress and anxiety. Common exogenous allergens also include inhalational, ingestive, contact, and chemical allergens. Food-based factors commonly include high-protein foods such as fish and shrimp, eggs, milk, beef and lamb, as well as food additives, preservatives, food coloring, etc. Common inhaled allergens include animal dander, hair, fungal spores, dust mites, powder mites, pollen, etc. Contact allergens include metals, chemicals, fragrances, etc. For recurrent eczema, the allergic factor may be internal or external to the body, and the specific allergens can be found by patch test or blood sampling and prick method.