You're poison:

Poison is one of the most irritating things about fighting the spiders and ghouls in Dark Messiah. Antidote potions aren't too common, and if you us﷽e one mid-battle you're likely to get re-poisoned immediately. Don't waste antidotes- just heal or potion yourself when you need it. Remember, spiders are susceptible to flames, and an adrenalin-boosted fireball speaks louder than a couple of crap daggers. The Altar of the Skull (Level 6) can be a real test of patience for poiso🀅n, and it's better not to fight when you can avoid it. Remember, you don't get rewarded on a per-kill basis.