For the purpose of investigating how IgE is correlated in the genesis of Atopic dermatitis (abbreviated as AD) micronizing method of RIST (necessary serum 10 microliter) was utilized. Serum IgE obtained from 369 cases AD, age ranged from 1 month old to 52 years old were studied. In 78 cases, IgE of the objects' parents were also studied as well. Serum IgE of the healthy control, age ranging from 3 days old to 49 years old, were studied and made comparison with those of the objects. Analysis was made in accordance with the factors like age, complication, disease type and prognosis. RAST (house dust, mite, egg, milk) and SKIN TEST (Scratch test) were carried out in order to observe the correlation between serum IgE and Specific IgE or to see the possible induction of eczematous lesion by specific IgE. The following were obtained as conclusion. Serum IgE of AD will show high level in significant manner in comparison with the healthy control from the time of infantile period. Low IgE group will show high rate of improvement after 3 years period of time. High IgE of parents will more or less affect serum IgE of their child or children. Correlation between serum IgE and the severity of AD is not noted in the infantile period but significant in the adult period. In the Scratch test immediate type of reaction could not induce eczematous lesion of AD. Induction of eczematoid reaction in AD was noted with high incidence following the Scratch test of Candida antigen. From the above it is assumed that in AD, although serum IgE level is high, induction of eczematous lesion could not be made by skin invasion of specific IgE antigen to the skin, pruritus by immediate type of reaction following release of chemical mediator will bring the tearing off the skin by scratch and invasion to the epidermis of inflammation inducing materials like human dander, sweat, bacteria or mycological agents eczematous lesion will start to take place.