Site of action of drugs in the treatment of atopic dermatitis. Cut of skin with, in bottom, the various stages. From left to right, erythematous stage in the trigger phase, by the allergen, vesicular stage, oozing stage, then crustal stage. A dilated blood vessel releases the mast cells and the cytokine releasing LTCD4 Th2 cells. The IgE produced by the lymphocytes will bind to the dendritic cells of Langerhans. In cartridge, the allergen sensitization phase on normal skin with the Langerhans cell that presents the allergen in the lymph node, triggering the production of LT4-secreting CD4 Th2 lymphocytes.