Being poisoned in OSRS is pretty dangerous since it takes quite a while to wear off and can hit over 99 hitpoints. The damage of the poison decreases by one, every 5 times you get hit by poison. It takes 18 seconds for poison damage to hit.  Bringing an antipoison potion is going to be vital if you want to fight the cave crawlers for a decent amount of time. You will have little chance to survive if you do not have food and the trip to the bank is pretty far.  They do drop the ingredients to make your own anti-poison, but you need to be lucky enough to get them.