The event where mushrooms, through an error in their natural biology, emit a caustic acid. This acid, although related to Caustic Soda use in refinieries, has the reverse effect of Caustic Soda. It is a rare phenomenon. The mushrooms has usually been exposed to a higher than normal dose of radiation or an irradiated substance. Irradiated fungicide will usually cause this. It is recommended that if you are to venture near these mushrooms, wear a radiation suit.
An example for Anticausticosis is not needed here.