Can you build up immunity to a spider bite?

I have been bitten by a brown recluse 7 times. The first time was the worst, because i didnt know what it was. Then when i learned to recognize the signs i caught it all the other times before it got worse and got it treated. I got bit a few days ago and the thing is almost gone already, no oozing stuff, no dying skin, no boil. I haven't gotten antibiotics or put any medicine on it. I am sure its a brown recluse bite because it started the same way as the others. Is it possible that i have built up an immunity to the poison or something?