Hello. Thanks for posting your query. The most basic cause of it is that your blood is not clotting properly, so it is spreading under the skin, and creating a bruise. This can happen for a variety of reasons, from vitamin deficiency in your diet to leukemia, which is a type of cancer. Bruising of this type is also sometimes normal for a person, you should have it checked out so you can rule out bigger, more serious problems. I advice you to see a doctor about it quite soon. Easy bruising is indicative of so many disease processes that it needs to be investigated promptly. Wishing you good health Regards. Dr saurabh gupta