A bruise on touch is the result of external force causing damage to blood vessels and blood flowing out under the skin. Frequent occurrences may be due to older age, poor vascular elasticity and brittleness, then vitamin deficiency, infection with viruses leading to shortened and reduced platelet lifespan, abnormal coagulation, etc.
Common disorders are trauma, thrombocytopenia, leukaemia, aplastic anaemia, malignancy, or abnormalities in clotting caused by taking certain drugs orally.