Made from olive oil, Castile soap was named for the Castilla region in Spain, and exported for centuries to royalty throughout Europe. It became famous as the "Queen of Soap", but is rarely found today.

It is undisputedly regarded as the mildest and most suitable soap for sensitive skin. In the past it was more widely available and recommended by midwives for newborns because of its well known mildness.

Castile soap is also used to launder antique lace and linen.

Redgum's entire Castile soap range is made using the traditional cold process method, whereby glycerin forms as a by-product of soapmaking. The Redgum method ensures that the nutrients contained in the high quality ingredients remain intact, and that the valuable skin softening glycerin remains in the final soap bar.