Bruising is a common skin injury that results in a discoloration of the skin. Blood from damaged blood cells deep beneath the skin collects near the surface of the skin, resulting in what we think of as a black and blue mark. Bruises typically occur when small blood vessels near the skins surface are broken by the impact of a blow or injury, often on the arms or legs. Harder blows cause larger bruises, but if someone bruises easily, even a minor bump can result in a substantial bruise. However, unexplained bruises that occur easily or for no apparent reason may indicate a bleeding disorder, especially if the bruising is accompanied by frequent nosebleeds or bleeding gums.

There are several causes that may lead to unexplained bruising, such as certain medications, nutrient deficiencies, and medical conditions. Some possible causes of random bruising include:

• Medications and supplements: Medications such as anticoagulants, nonsteroidal anti-inflammatory drugs, and corticosteroids reduce the blood’s ability to clot. This may result in blood leaking from vessels and accumulating under the skin. Some studies suggest that certain dietary supplements, such as fish oil, garlic, and ginseng, may also be factors in bleeding and bruising.

• Bleeding or clotting disorder: Underlying bleeding disorders, such as hemophilia, thrombocytopenia, or factor V deficiency, can cause bruising. Hemophilia is a genetic condition wherein people lack either clotting factors VIII or IX, which can cause excessive bleeding and bruising.

• Nutrient deficiency: A deficiency in certain nutrients, such as vitamin C, vitamin K, and iron, can cause easy bruising.

• Medical conditions: Certain medical conditions, such as liver or kidney disease, leukemia, and lymphoma, can cause unexplained bruising.

If someone is experiencing unexplained bruising, it is important to be on the lookout for additional symptoms that may indicate an underlying condition. They should see a healthcare provider if they have frequent, large bruises, especially if their bruises appear on their trunk, back, or face or seem to develop for no known reasons. They should also see a healthcare provider if they have easy bruising and a history of excessive or prolonged bleeding, such as after a minor cut or during a surgical procedure, or if they suddenly begin bruising, especially if they recently started a new medication. A healthcare provider can help determine the cause of the bruising and recommend appropriate treatment.