As per Monster Manual V 3.5E about the Ryklar
Contaminate (Su) A rylkar harridan exudes toxins that
contaminate the environment around it. Food or drink
brought within 20 feet of a harridan becomes foul and
poisonous (Fort DC 22, 1d6 Con/1d6 Con) to any but
rylkars. Potions in the area must...