The appearance of purple bumps on arm tapping may be an accidental injury due to some people’s misconceptions about health. Because often encounter or see some people use both hands to both sides of the arm pat, think that this is the way to activate blood circulation or is beneficial to health, this pat on the health of whether there is no authoritative affirmation. So there is no scientific basis for this, but some people often beat this, resulting in subcutaneous bruising or even subcutaneous hematoma on the outside of both arms. So if this situation arises, try to avoid patting, which is caused by trauma.