NYC dermatologist Dr. Shereene Idriss is sharing a simple, free test to determine if you have oily, dry, or combination skin. N_studio - stock.adobe.com You may need a thick skin to take this test.

Your doctor can usually tell if you have psoriasis without a biopsy-- a procedure that collects skin cells and checks them under a microscope ... bumps, and thick scaly patches called plaques.