I used to get lots of spider bites and it turns out they were in my mattress. once I got rid of that mattress (via a move to college) then I never had the problem again - well, until I visted my dad again and slept on that fucking mattress.
it wasn't bed bugs, mosquitoes or anything else, def spiders and my dad never did anything about it b/c he said the spiders got rid of the other bugs. fuck that, they bit me the fuckers.
and the stuff oozing out of your leg isn't anything foreign, it is just that the stuff they shoot in there causes inflammation and if I recall correctly your immune system doesn't know what to do and attacks the skin there and so you have a little war going on and the stuff running out is the waste from the war. mostly blood plasma and some white blood cells if 1) I'm remembering it correctly, and 2) the article I read it in was correct in the first place