We know that most tarantula bites are not a big deal for people as tarantula's venom is not that toxic. It's not a fatal event. It's usually localized swelling.
So cold water compresses are the first line of defense. Keeping cold water on, keep the swelling down works. Just like a bee sting. Sometimes you want to put witch hazel on there. That'll take the sting away from there as well.
But if you find yourself getting dizzy. If you find yourself having labored breath all of a sudden, you could be allergic to the venom that was just injected into you. And that's a medical situation that requires immediate care. That's an emergency situation. That's anaphylactic shock, potentially, setting in. And you've got to get to the emergency room and get something to counteract that.
But usually a tarantula bite is in the hand. Usually it's very localized. And any kind of a cold compress that you would use for a bee sting, witch hazel again is the treatment. Rashes from a tarantula are potentially allergic reaction but usually the rashes and the itching that comes from it, and I'm holding tarantulas today so I've got it, comes from those urticating hairs. Those are terrible. Little tiny hairs that are digging into the pores of your skin and lodging. If they get into the soft tissues of your nose, your lips, your eyes it can be extremely irritating. That's got to be taken off with running cold water and then of a patting motion to pull those hairs off your body. You don't want to really rub it in or scratch it in like I just did, because you're digging it further into your skin. You want to get it off with a patting motion. Almost like a bandaid on top of it. Rip those little hairs out. Piece of scotch tape or something to get them off if you know where they are.
Oftentimes it's so miniscule and so small it's hard to find. Certainly, taking a cold shower, little soapy water isn't going to hurt any to get them off you as well. But that's the first line of defense. Is to pat your body, take those hairs off. Cold water for a bite.
And really know your species. Don't try to handle one that's going to have the potential to bite you or the potential to flick his hairs. Leave them be.