Everybody has occasional bruising after minor trauma or even without a noticed trauma at all. There is large inter-individual variation in sensitivity. Solitary bruises, even without a noticed trauma, are usually harmless and do not necessarily require further laboratory investigations. Keep in mind that purpura can be caused by meningococcaemia or other severe infection (often febrile patient in poor general condition) and in such a case arrange for immediate further treatment. Other causes to be investigated and treated include autoimmune diseases, medications and increased bleeding tendency.