Schick test

The Schick test, developed in 1913, is a skin test used to determine whether or not a person is susceptible to diphtheria. It was named after its inventor, Béla Schick (1877–1967), a Hungarian-born American pediatrician.
Procedure.
The test is a simple procedure. A small amount (0.1 ml) of diluted (1/50 MLD) diphtheria toxin is injected intradermally into one arm of the person and a heat inactivated toxin on the other as a control. If a person does not have enough antibodies to fight it off, the skin around the injection will become red and swollen, indicating a positive result. This swelling disappears after a few days. If the person has an immunity, then little or no swelling and redness will occur, indicating a negative result.
Results can be interpreted as:
The test was created when immunizing agents were scarce and not very safe; however, as newer and safer toxoids became available, susceptibility tests were no longer required.