Final answer:
Psoriasis commonly affects the elbows, knees, scalp, back, face, palms, feet, and sometimes nails, but the area by the mouth is NOT one of the most commonly affected areas.
Step-by-step explanation:
The question concerns which area is NOT one of the most commonly affected by psoriasis. Psoriasis is a skin disease that typically causes itchy or sore patches of thick, red skin with silvery scales. The most commonly affected areas include the elbows, knees, scalp, back, face, palms, and feet.
Some individuals also experience psoriatic changes in their nails. However, psoriasis less frequently affects the skin around the mouth. Thus, the area by the mouth is NOT one of the most commonly affected areas by psoriasis.