Effect of intradermal tuberculin tests on BCG-induced allergy.

Trials are going forward to determine whether intradermal tuberculin testing with 10 TU at yearly intervals after BCG vaccination may prevent waning of BCG-induced allergy in schoolchildren. Meanwhile, two experiments to the same purpose, carried out in guinea-pigs, are described. They show that waning allergy in guinea-pigs can be sustantially enhanced by intradermal injection of either purified tuberculin or Old Tuberculin, the effect lasting for at least 8 weeks, even with so small a dose as 5 TU. It is pointed out that this enhancing effect has been demonstrated only in BCG-vaccinated guinea-pigs and that it is not known whether the same phenomenon would occur in guinea-pigs infected with living human tubercle bacilli.