Chronic fatigue syndrome, mast cells, and tricyclic antidepressants.

A pet litter material comprising a mixture of bentonite clay and expanded perlite, the mixture having a bulk density of from 650-950 Kg/cubic metre. The bentonite clay may be calcium bentonite clay, sodium exchanged bentonite clay, or a mixture of both of these types of clay. A method of producing the pet litter material is also described.