About eighteen years ago, when I was at high school, we all got HEAF skin tests for any previous exposure to tuberculosis. I tested negative, as far as I know. The indentations from the test remained on my arm through the years. Just lately, the old mark has gone crazy. It went red, blistered and then turned into a scab. I am subject to a lot of mosquito bites, so this may be coincidental, but it didn't feel that way and I don't recall being bitten. Is there any other possible significance to this?