Many prescription and nonprescription medicines may reduce your blood's ability to clot and cause bruising or bleeding under the skin. A few examples are:

• Aspirin and other medicines (called blood thinners) that prevent blood clots. Also, taking a nonprescription medicine with a blood thinner may increase your risk of bruising and bleeding.
• Medicines used to treat cancer.
• Nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen (for example, Advil or Motrin).
• Steroids, such as prednisone.