My boyfriend has this huge like boil on his back it started like a huge bite know its spreading and look like his flesh is being eaten or something!! He went to the hospital and they gave him antibiotics but look as if its getting worse what should we do

Go back to the ER!

If it's getting worse, you need to go back.

Some spider bites can cause Necrotizing fasciitis in rare cases and this needs to be treated before it becomes too serious.

If it IS a spider bite and it is necrotizing, this is nothing to play around with or wait on.

Thank you for that I really think that is the case in this matter!! I wish that I could send you a picture of the wound to really show you.

It may be cellulitis, not spider poison. Bacteria move into the large hole left by the bite. I had that, and oral antibiotics didn't work. It spread over my entire leg and the skin died around the bite, turning black and flaky. I had to have drip antibiotics in the ER.
That was 3 years ago. I now have a lot of inflammation (like arthritis) all around the bite and down to my foot. Plus I am prone to rashes under my arms and breasts and at the top of each leg. That doesn't mean that bacteria remain (I'd have died of sepsis if bacteria had gone deep into the body). It is the body's reaction to a foreign invader.