A lot depends on whether or not the blood is fresh or dried out. Bloodstains are easier to remove if they are fresh. First try a mixture of equal parts starch, hydrogen peroxide and salt (household salt is fine). Rub this into the stain then leave it to dry. Once dried, clean it off. If the stain is old and dried in, dampen it with some water first – dampen it, don’t flood it! Another option for bloodstains, fresh or dry, is an enzymatic cleaner. This should break down the blood proteins making the stain easier to clean. Once a stain has dried out it is more difficult to remove. However, the above suggestions should solve your problem. Once an application has dried out, you should be able to vacuum or brush it off the mattress.