Psoriasis is a chronic skin disorder that affects 1% to 3% of the world's population. It is characterized by periodic flare-ups of well defined, red patches covered by a silvery, flaky scale on the extensor surfaces and the scalp. There are several variations of psoriasis but the most common type is chronic plaque psoriasis. The exact cause of psoriasis is unknown, but it is believed that a combination of several factors contributes to the development of this disease.

Diagnostic Essentials for Psoriasis in TCM:
(1) Primarily, skin lesion is manifested by red inflammatory papules in size from needle tip to mung bean, often in drip shape, and enlarges swiftly and is covered with layers of silver white scale. After scale is striped , it is possible to see a film phenomenon and petechial hemorrhage (Auspitz phenomenon), with basal infiltration and isomorphic reaction.

(2) During the development, skin lesion can be manifested by coin shape, map shape, circle shape, band shape, conch shape, and even wart shape.

(3) It occurs frequently on the scalp and extension aspect of the four limbs, mostly on the elbow joint and often in the whole body.

(4) Pitted depression can be seen in the nail in some patients, with the nail thickened and luster disappeared in severe conditions.

(5) Fascicular hairs are present in those with the problem on the scalp.

(6) Enanthem exists in some cases.

(7) It starts slowly and recurs frequently, usually aggravated in winter and relieved in summer, accompanied by family history and spontaneous pruritus.

(8) Symmetrical erythema can be seen in the palmar and plantar region in the pattern of palmar and plantar pustulosis, with many aseptic pustules in size from needle tip to millet grain.