Seborrheic dermatitis is a skin disorder that mainly affects the scalp, causing itchy, yellow or white patchy scales or thick crusts that may attach to the hair shaft, as seen in the lower left side of the image.
Your doctor may recommend topical creams, ultraviolet light therapy, or oral medication to help restore skin color and stop the spread of white patches. Skin grafts are also effective for getting rid of small patches of white skin.
The scalp can become infected if fungus or bacteria enter the scalp through the hair follicles or damaged skin. Skin damage can result from common skin conditions, such as psoriasis and eczema. Bacteria cause some common infections, such as folliculitis and impetigo.
Oral retnoid can treat scalp folliculitis.
Read up on Morgellons.