Possible causes of bruising include:
* Blood disorders, including problems with blood clotting such as hemophilia A or hemophilia B
* Blood-related diseases such as leukemia
* Liver disease, such as cirrhosis
* Lymphomas
* Certain disorders in which bone marrow cells grow at an abnormal rate
* Nutritional deficiencies, such as deficiency in vitamins C, K, B12, or folic acid
* Sepsis, or severe infection in the bloodstream
* Systemic lupus erythematosus (SLE)
* Trauma, injury or physical abuse
* Prolonged coughing or vomiting
* Medications, such as blood thinners
* Surgery or other medical procedures
* Allergy-related disorder