A transdermal injection appliance has a pad impregnated with a disinfectant solution such as alcohol, a body with adhesive for holding the pad against the skin of a patient, and a sleeve with a guide passage through the body for guiding an injection needle. A membrane puncturable by the needle is attached to the sleeve to close the passage, the membrane being self-sealing so that an opening through the membrane formed by the needle is closed as soon as the needle is extracted, thereby wiping a majority of blood from the needle and preventing the escape of blood. The tubular sleeve can have an outer end with a coupling for connection to a retractable needle injection assembly. A method of using the appliance with the retractable needle assembly to administer medication without exposing the health care giver to accidental contact with the needle is also disclosed.