Negative buffs (also called debuffs) such as diseases, poisons, curses and magical effects (like polymorph and some DoT spells) can be removed Eve isk by primary healers. Priests can use the spells 'Cure Disease' (and later 'Abolish Disease') to remove diseases from players. They can also use 'Dispel Magic' to remove magical debuffs, which is a great asset when you hit your 40s and beyond.