Bruising occurs when blood leaks from the capillaries, usually due to a blow to the body, creating an area of discoloration which is visible through the skin until the leaked blood is reabsorbed. While it can be worrisome if you seem to bruise for no reason, even bruising which appears to be spontaneous generally has some source, and thus is generally not a major cause for concern. If you seem to bruise for no reason, you may actually have thinning skin or weakened capillaries. It is also possible that a medication is causing you to bruise, or that you are suffering from a blood disorder. Finally, your bruising may be caused by an injury so minor that you simply forgot about it.
If you seem to bruise for no reason, you may in fact be experiencing a side effect of thinning skin or weakened capillaries. Many people are affected by one or both of these conditions as they age, and each makes the body more susceptible to bruising. Skin which has begun to thin offers reduced padding against bangs and bumps, and weak capillaries are more likely to leak blood than healthy vessels. While bruising caused by these conditions can be uncomfortable or unsightly, it is generally not a serious issue, and thus should not be a cause for concern.
Another factor that can make you seem to bruise for no reason is a reduction in your blood’s ability to clot. Sometimes, clotting issues are caused by a medication, particularly one which is intended to thin your blood. In rare cases, clotting issues can be a symptom of a blood disorder. If you have begun to notice unexplained bruising and have recently started a new medication or are young and otherwise healthy, you should consult your physician. She may adjust your medication, or may run tests to determine whether a blood-related issue is responsible for your bruises.
Lastly, a bruise which seems to have appeared for no reason may actually be the result of an injury so minor that you simply took little notice of it. For instance, you might have banged your leg as you got up to use the bathroom during the night. If your unexplained bruise occurs as an isolated incident and fades away within a few days, there is a good chance that it was caused by a forgotten injury and is therefore not a cause for worry.