What harm can just a "little" black mold do?

Before I moved into my apartment a year and a half ago, I looked around and noticed that in the bathroom above the shower/tub, there was a line of spotted black mold growing, and even some on the sides of the walls. Well, I moved in and was "told" it was taken care of. Now, just a few months ago, it reappeared in the same places! My six year old son and I have both been getting red colored skin, that comes and goes. I've gotten a few rashes here and there. The tops of his hands, mainly below his knuckles on the "fatty" part are a light red and his cheeks and chin on his face have now a red tint. And now between the both of us, we are getting red colored, irritated eyes. The only parts of our eyes that are red is just the main front part where the eye is open. When I raise and lower our lids, the rest of our eyeball is white. Had him to the doc today but didn't get much of a response. I was wondering if these could be from the mold, or do you guys have any other suggestions of what it may be?