The bruise color is considered purpura, which is a subcutaneous bleeding spot. There are three common causes: first, large vascular fragility, mostly seen in children, women and the elderly; second, trauma, perhaps minor trauma cannot be noticed, or strenuous activities such as climbing; third, coagulation dysfunction. You can recall the recent history of trauma and the high risk of vascular fragility according to your own situation, if none of them and purpura occurs repeatedly, you need to improve blood routine and clotting time. Life pay attention to rest, avoid over exertion, more kiwi, orange, strawberry and other fruits rich in vitamin C.