The skin condition characterized by red patches covered with white scales is psoriasis. It is a chronic, immune-mediated inflammatory disease in which skin cells are produced and moved to the surface much faster than usual, creating thickened plaques with silvery-white scaling.
The most common form is plaque psoriasis, also called psoriasis vulgaris. It often affects the elbows, knees, scalp, and lower back, though it can appear elsewhere. Psoriasis is not contagious and cannot be spread by touching someone who has it. Its severity can range from a few small patches to extensive disease, and symptoms may flare and then improve.
The condition is distinct from ringworm, which is a fungal infection, and rosacea, which commonly causes facial redness and sometimes bumps. Eczema can also produce red, itchy patches, but its typical appearance and underlying mechanisms differ. Some people with psoriasis also develop psoriatic arthritis, an inflammatory joint condition. Triggers can include stress, skin injury, infections, and certain medications, although triggers vary from person to person.