Hairless Xolos are the dominant expression of the heterozygous Hh hairless trait. The stems are smooth, hairless, or slightly hairy. Young branches have whitish resin warts and the twigs are slender, hairless, and often pendulous. Anal aperture flattened with a hairless horizontal slit. There are concerns as to whether breeding hairless and tailless rats is ethical. Most litters contain both hairless and coated puppies. Cats with food allergies may present with red, hairless, and scabby skin. Dark patches cover his hairless, waxy head. These are often called "naked" or "hairless". Lykoi vary from completely covered in hair to partially hairless. He next awakes upon the shores of a mysterious river, naked and hairless. In Peru, breeders tend to prefer completely hairless dogs. There are reports of stray Mexican Hairless Dogs being mistaken for chupacabras. Similarly, there are several breeds of hairless dogs. The breed occurs naturally in two varieties, hairless and coated.