Eczema, dermatitis belongs to the allergic skin disease, the cause is very complex, food factors are very important, there are many other factors, so for eczema, dermatitis to avoid mouth is not absolute. The actual allergens are not so easy to discover clinically, but of course those who have the conditions can go to the hospital for allergen testing. Before the allergen is found or detected, the patient can use the food exclusion method to find the allergen, first eat the simplest, less allergic food for 1-2 weeks, if no aggravation of the lesions is found, gradually add another, if in the process of adding food, the lesions are aggravated or itching is obvious that may be allergic to a certain food, then avoid the added food, if the lesions and symptoms are not aggravated after eating the suspected allergenic substances, then it is not necessary to avoid the mouth. Then it is not necessary to avoid the food. One should think about whether there are other intrinsic or contact factors causing the allergy. If the eczema suddenly appears all over the body, which is what we call in the acute stage of development, it is best to avoid all allergic substances, such as sea food, spices, beef and mutton, before you have time to find the allergen. In short, the mouth is to prevent disease, but should not be without analysis and all avoidance, which can cause malnutrition, but not a good effect on the treatment of disease.