[A village charmer or ‘pellar’ from a Cornish town] can only pass his charm onto a member of the alternate sex, and once passed, [it] cannot be recalled. The “alternate sex” belief is of course a widespread one: for instance, at the Men-an-Tol in Cornwall, where children are passed through the hole as a cure for certain ailments, a boy must be passed by a woman to a man, and a girl by a man to a woman.
Present-Day Charmers in Cornwall
Charles Thomas
Folklore, Vol. 64, No. 1. (Mar., 1953), pp. 304-305.