it's caused by bad genetics. in breeding animals (especially pets), where appearance is a priority. in humans, this is rescuing people who are prone to allergies (inherited, acquired) and allowing them to resell defective genes. I know it sounds awful, but it's just that people just survive who would otherwise - in normal natural conditions, die. and worse, they have offspring. from the point of view of the individual it sounds disgusting, unfortunately, from the point of view of the species (homo sapiens) as well - because it is a path to degeneration and extinction. (tuxedo)