And for my money, the best show in TV's greatest decade was Lost in Space. It's impossible to describe what watching this show was like in the 1960s. It's an experience that simply can't be re-produced today.
The reaction reaches its peak about 48 to 72 hours after the PPD is injected. Waiting too long or not long enough may cause an underestimation of the reaction and, therefore, affect how the test is read.A positive test will cause redness, itching and a raised, hardened area of skin called an induration.
What I am wondering is how long after exposure a PPD would give a pertinent positive/negative so I can schedule the doc appointment for that time, if its an immunological test it should take some until my immune system is primed I'm just missing the clinical picture of when it is primed. Thanks. Mar 13, 2009. #1.