Goldberg says this is one of his favorite questions—mostly because he assumed it was too ridiculous to be true. While writing Why Do Men Have Nipples?
, Goldberg and Leyner pored over medical textbooks and studies to find out that some people have a strange reaction to blazing sunlight that brings on an uncontrollable sneezing fit. This is due to something called the photic sneeze reflex—also known as autosomal dominant compelling helio-ophthalmic outburst, or ACHOO. A 2005 study of six Spanish families showed that there are usually two to three "achoo"s per episode of ACHOO
. This reflex is relatively under-studied and not completely understood, says Goldberg, but it is thought to have something to do with an accidental crossing of nerve signals.