eternal mantoux

Hey...I had a mantoux done 8 days ago. It was read as negative, as the ones done over the past 10 yrs have been(high risk group, so they say). My question is: the redness around the test area has remained, well, pretty red, is this a cause for concern? There is no lump associated with the spot, it doesn't itch...its just unattractive. I do have psoriasis-fairly light-but it does not look the same.
Any help is appreciated as an ease to this semi-hypochondriac.