Ok, let's separate a few things first. You can get a toxin exposure through injestion, meaning you accidentally eat it (poor handwashing, reuse of kitchen gear, etc). In this case we would expect either gastrointestinal symptoms (if you injested some nassty bacteria such as Vibrio or Salmonella), or systemic ones--things all over your body, much of the times these are neurologic (tingling, heart or respiratory abnormalities). OF course there are many more manifestations, these are just examples.
The second route of entry you mention is a break in the skin--either from getting cut in the tank itself, or from a previous cut. This is where you often get localized rashes, infections etc, often originating at the point of entry. I can't say what this is just from "a stinging rash", but I'll throw out some possible things it could be.
Now, you are citing a finger as a point of entry, and a rash in the crease of the elbow, which is pretty far away to have nothing in between the cut and the rash. I'd think it's more likely that there was direct contact of something (tank water or otherwise) with that area. If it were from the tank, perhaps you had your arm in all the way and got stung by something--hydroids, anemones, sweeper tentacles are all good candidates for this. If that were the case though, the symptoms would have come on pretty soon after exposure. If you rubbed that area on something in the tank and abraded it enough to cause a break, a bacterial infection is possible too (eg Staph), and that fits with the delayed onset of symptoms. I'd expect it would also be a bit swollen and hot in the area, signs of inflammation.
So, what could it be? Possible it is from the tank, but also possible not. Creases of the body can sometimes retain moisture and cause a skin rash from being continually wet, and that is how that would manifest--redness and sting--but unless you really haven't been moving at all it's unlikely your elbow stayed wet enough for that to occur. Inflammation can be mitigated with icing and antiinflammatories, but that will treat the symptom and not the cause. I'd consider going to the doctor if it does not improve or gets worse, or if you start to have any systemic symptoms. They will be able to look at the rash and tell whether it is infection, allergy, sensitivity or something else. My concern is not the rash--again, that annoyance is easily treated. I just would want you to make sure the rash isn't indicative of something more serious and progressive.
So take photos if you can (pictures make figuring things out easier), and keep us posted! |