A purple spot on the thigh indicates a subcutaneous bleeding condition. In clinical practice, purple spots on thighs are commonly seen in the following three situations: first, bleeding spots on legs caused by trauma, this condition is due to trauma causing capillary rupture and bleeding, there is usually no special treatment, you can apply local heat to promote the absorption of bleeding. Second, purple spots caused by simple purpura, this is a common disease related to women, often no obvious cause, purple spots on the legs, and hormone concentration changes are related, take vitamin C effect is good. Thirdly, allergic purpura, which is a kind of bleeding caused by increased capillary permeability and fragility due to allergy to external factors, is generally treated well by taking vitamin C and glucocorticoids, and is usually cured after about two weeks.