The Dick test is a laboratory test designed to indicate whether or not a person is immune to scarlet fever. Scarlet fever, at one time fairly common in children, is a disease named for the flushed face, red rash, and fever it causes. The Dick test is named after Georgeand Gladys Dick, American bacteriologists who worked on the diagnosis and treatment of scarlet fever in the 1920s. The test involves administering two different injections, one into each arm of a patient. In one arm, toxin taken from a culture of scarlet fever bacteria is injected; in the other arm is injected neutralized toxins which act as a control. If the toxin causes redness, tenderness and swelling after 24 hours, the person is not immune to scarlet fever. The control normally shows no swelling for comparison.

For isolating the streptococcus bacteria that causes scarlet fever, and for the preparation of an antitoxin for the treatment of the disease, George and Gladys Dick obtained a British patent in 1924 and a U.S. patent in 1925. Armed with this test and the antitoxin, doctors could diagnose and treat the disease much more efficiently, resulting in a decline in the number of cases. As the age of antibiotics arrived, scarlet fever was successfully treated with antibiotics and thus the number of cases dwindled sufficiently to make it fairly uncommon today.