I don't recall anyone mentioning it here specifically, but I just did a quick search for
-- lyme secondary rash --
and got quite a few hits that say it's not uncommon to have that symptom.
I get secondary lyme rashes in the same area i was originally bitten. Has anyone else had this happen?
The lyme ras is called erythema migrans, migrans meaning it moves about (like migrate).
It can appear anywhere on the body and it means the lyme has spread through the body. As far as I know, there is no proof that the location of the rash indicates you have a particularly intense zone of infection in that part of the body. Lyme disease can pick on any body organ and, as you say, the skin is just another organ.
It's a good question for a doctor ... but here's my guess (since I'm not medically trained) ... different infections the "Lyme" ticks bring have different manifestations.
Lyme (sometimes) produces a spreading, circular rash that clears in the center, leaving a 'bullseye' appearance, and then fades after a while (this is just what I've read ... I didn't get a rash, but I had Lyme).
Another infection (Bartonella) often produces a different sort of rash, one that looks streaky and comes and goes (so I read, since I didn't have 'Bart').
The circular infection in Lyme is just where the body's reaction shows up at the point of infection, but the bacteria are busy spreading throughout your body ... tho the symptoms then vary from person to person, and sometimes it's because of different strains of Lyme -- some are more neurological, some are more in the joints, and so on.
Are there then clusters of bacteria in the different parts of the body, while other areas of the body remain clear? Maybe, but I don't know that it matters except to help the doc diagnose which diseases you may have.
The rash in Lyme (and perhaps in Bart too) is your immune system reacting to the invading bacteria, producing inflammation. It's a symptom, and remember to tell the doc you see about what rashes you got and where and how the spread or didn't. Take cellphone fotos of the various rashes and stages if you can ... a good doc may be able to derive a better sense of your situation with visual evidence like that.
Bottom line, tho: don't let it worry you. If you are infected, you're infected and the treatment will not change, tho the observed rash may help the doc in diagnosis and therefore what treatment to follow. Hope that helps. It's certainly a good question ... but remember: I'm not medically trained!!