Jennifer Lawrence has often appeared in public with a scarf wrapped around her head or neck, but the actress has clarified that this detail has nothing to do with fashion. Whether it's a silk scarf or a thicker scarf, the accessory has a practical purpose. In a new interview with Vogue, Lawrence revealed that she uses it to cover up melasma spots, a skin condition that causes darker spots to appear. The actress explained that she has started usi…