Wood Ash Lye is a fluid from The Vegan Option. Wood Ash Lye Buckets can be used to create Soap.
Standing in Wood Ash Lye causes 0.25 points of damage (1/4 heart). If an entity dies from Wood Ash Lye, the death message will state <entity> bathed in lye [whilst trying to escape <other entity>].
1,000 mB of Wood Ash Lye fluid can also be crafted by crushing a 1,000 mB of water with 3 wood ashes (ashWood Ore Dictionary entries) using a Piston in-world.