Atopic dermititis, also known as eczema, is a chronic fluctuation disease of the skin that has itching as its cardinal sign. It is considered atopic because of its tendency to occur with other allergic type disorders including allergic asthma and allergic rhinitis. The rash has a definite familial tendency and is non-contagious. The distribution and look of eczema can vary from a dry red bumpy rash to a wet oozing eodematous rash that easily becomes infected.

Psoriasis (psora is greek for “to itch”) has been diagnosed in both Asia and Europe for over 2000 years. In China it is known under the names Pi Xuan (Ox Skin Dermatitis), Song Bi Xuan (Pine Skin Dermatitis), and Bai Bi (White Dagger Sore/ Whiite Crust), all of the names pointing out the characteristic scaly look of this common skin disorder. The scale itself comes from the over production of skin cells that are regenerating every 3-5 days, instead of the normal 30 days.

Many substances have been identified as itch "triggers" in patients with eczema, and triggers are not the same for every person.

Although eczema may look different from person to person, it is most often characterized by dry, red, extremely itchy patches on the skin.