Do you find mystery bruises periodically on your body despite not remembering bumping into things? To understand why you get bruises, it’s important to understand what they are: when you bump into something with enough force, the blood vessels underneath your skin can break, causing blood to leak out of them. This results in the purple, bluish marks that appear on your skin in the next few hours to days. However, you don’t have hit your leg or arm hard to cause a bruise, as there are certain things can make those blood vessels more susceptible to bruising. Below are some reasons you may bruise easily.

You spend too much time in the sun.

Harmful UV rays from the sun can cause collagen—the spongy tissue in the second layer of your skin—to dissolve. Collagen acts like a cushion to protect the network of blood vessels. Without the buffer of collagen, your blood vessels are more likely to rupture.

You’re getting older.

Bruising easily is common among older adults due to aging capillaries and thinner skin.

You take certain medications.

Blood thinning drugs, including aspirin, can cause you to bruise more easily. Similarly, some dietary supplements, or a lack of vitamins B12, C, K, and folic acid will also make bruises bigger and more severe.

You drink alcohol.

Alcohol is a vasodilator, meaning it causes your blood vessels to temporarily relax and expand. This widening increases blood flow through your body, which means that more blood can escape if a blood vessel happens to get ruptured.

While most bruises go away on their own, you can always ice the area immediately to slow down the blood flow. Tylenol (which is NOT a blood thinner) can be taken to reduce pain and swelling. However, if you’ve had unusual or unexplained bruising for more than two weeks, talk to your doctor to rule out anything more serious. In rare cases, persistent, unexplained bruising can be a sign of a serious illness, such as type 2 diabetes or leukemia.