The breed occurs naturally in two varieties, hairless and coated. Hairless Xolos are the dominant expression of the heterozygous Hh hairless trait.[18] Coated Xolos (hh) are the recessive expression, and breeding hairless to coated or hairless to hairless may produce pups of either or both varieties. Breeding coated to coated will only produce coated pups because they are recessive to the hairless trait and do not carry the dominant H gene.