Going overseas soon and got a TB shot. What’s in it and why did it give me this red spot that will turn into an ulcer according to the nurse … ?
I assume you’re getting a TB skin test. A small amount of antigen which is also present on the TB bacteria (but will NOT cause a TB infection) is placed under your skin. If you have in the past been exposed to TB and have had it take up residence in your body (where it may lay dormant for years or decades), you will have antibodies to the TB antigen. This will cause swelling at the site of the injection between 48-72 hours, which should then resolve. If you have minimal or no swelling at the site, you are most likely TB-free.
It is possible to have a very strong reaction to the TB test, and on rare occasions, the inflammation is so great a scar can result, but this is not at all common.
It is possible to have a local allergic reaction to components in the TB skin test. If this is the case, swelling may be immediate. But it should be absent well before the 48-72 hour timeframe when the TB test is read, and does not indicate a latent TB infection.
If your skin test comes up positive for a TB infection, your doctors will look for signs of TB disease; a chest x-ray to look for tuberculous lesions, and a quick medical history about night sweats and weight loss.
If there is no sign of TB disease, but only TB infection (TB lying dormant in your system) you’ll probably take the antibiotic INH every day for 6-9 months, which is over 95% effective in eradicating the TB bacillus. Vitamin B6 (pyridoxine) is often given along with it to minimize side-effects of the INH.
If you have active TB disease, then you’ll be getting intensive medical therapy for quite a while, and probably won’t be going overseas.
The above represents the standard of care in the US for TB skin testing, with lots of stuff left out. I can’t guarantee it’ll be the same in Oz.
QtM, MD
I assume it’s still the BCG vaccine. I had 3 of these while working with TB patients because the first two didn’t register later as heving exposed me to TB. I don’t recall any significant ulcers.
I assume it’s still the BCG vaccine. I had 3 of these while working with TB patients because the first two didn’t register later as heving exposed me to TB. I don’t recall any significant ulcers.
Oh. I think the “Mantoux test” I had before in my forearm was the skin test you’re talking about. At least, I had a second shot more or less a week or so later, in my shoulder. Just wondering why the second shot causes an ulcer. 
Ah, the BCG vaccine. We don’t use it much in the US. Interesting little article here on Is the BCG vaccine any good?
Whatever you do, don’t get a Mantoux test ever again. It will be positive, possibly extremely so.
The literature says the ulcer is due to “an excessive response to the BCG vaccine”. Something in you must really not like the vacine.
At the hospital where I work, I am required to get a TB test every year (even though I don’t actually work IN the hospital). I just had one on Friday and I’ll be damned if I can even find the spot where they poked me. This is a good thing, though.
As I said in my post, before working in the TB ward I was required to show a positive Mantoux. I had 3 BCG injections before I showed positive. This was by no means unusual. I don’t see how the Mantoux can be more positive than positive - it only indicates your prior exposure to the bacillus.
Sorry, I should have said “It stands a good chance of being extremely positive”. Being “more positive than positive” can be quite painful , and has resulted in the loss of a limb in rare occasions in the past.
But your experience shows one of the flaws of the BCG vaccine. It’s protective in less than 70% of cases.
Sort of a hijack, but how is it that you can keep getting Mantoux tests without getting sensitized to the antigen?
Back in school in the early 70s I came up positive in the “HEAF” test (UK) and didn’t have to have the BCG jab. There was no follow-up - no testing for TB, no antibiotics, nothing. Should I be worried?
Julie