Skin conditions. Really should check out the american academy of dermatology for in-depth description. Briefly, psoriasis tends to be an autoimmune disease. Eczema tends to be an allergic disease. Seborrheic dermatitis is thought to be due to a combination of an over production of skin oil and irritation from a yeast called malassezia.
Dermatologist. Not even family physicians can tell the difference in some difficult cases. Generally speaking, seb derm usually involves scalp and face. Itching is mild. Eczema can be anywhere of the skin and depends on type of eczema. Itching is very common. Psoriasis typically presents over elbows, knees and scalp. In severe cases, arms, legs, body can be involved. Itching may be none or mild.