Bruising on the hands for no reason may be caused by other factors such as purpura simplex, purpura anaphylactica, thrombocytopenic purpura, and vitamin deficiencies. 1. Purpura simplex: the hands of bruises for no reason may be purpura simplex, the cause of which is not yet completely clear, may be related to hormone levels, coagulation abnormalities, capillary wall abnormalities and other factors, common in menstruating women. 2.Allergic purpura: Bruising on the hands for no reason may also be allergic purpura, which may be related to genetic factors, bacterial and other pathogenic infections, penicillin and other antibiotic drugs, and many other factors. 3. Thrombocytopenic purpura: Thrombocytopenic purpura may be related to immunity, heredity, infectious diseases and other factors, patients with thrombocytopenia, which leads to blood clotting dysfunction, the hands will be bruised for no reason. 4. other: in addition to the above factors, vitamin C deficiency can lead to changes in the permeability of blood vessels, which will appear on the hands of bruises without reason. There are many reasons for unexplained bruising on the hands, and it is recommended to consult a doctor in time to avoid delaying the condition.