Final answer:
The two sites for intradermal injection are the inner forearm and the upper back, which allow for clear observation of any potential reactions.
Step-by-step explanation:
The two sites used for intradermal injection are the inner forearm (Vf) and the upper back. The inner forearm is a common site due to its convenience and the thinness of the skin, which makes it easier to observe any reactions. The upper back, in the area between the shoulder blades, is also used especially for tests such as tuberculosis skin testing. It is not recommended to perform intradermal injections in areas such as the glabella (Gb), alar crease (Al), external auditory canal (Ea), nares (Na), manubrium (Mb), axillary vault (Ax), antecubital fossa (Ac), interdigital web space (Id), hypothenar palm (Hp), inguinal crease (Ic), umbilicus (Um), or toe web space (TW).