"It must be considered what harmes and perils come vnto men by this beast. It is most certaine that the breath and sauour of cats consume the radicall humour and destroy the lungs, and therefore they which keepe their cats with them in their beds haue the aire corrupted and fall into feuer hectickes and consumptions. There was a certaine company off Monkes much giuen to nourish and play with Cattes, whereby they were so infected, that within a short space none of them were able either to say, reade, pray, or sing, in all the monastery... the haire also of a cat being eaten vnawares, stoppeth the artery and causeth suffocation... to conclude this point it appeareth that this is a dangerous beast, & that therfore as for necessity we are constrained to nourish them for the suppressing of small vermine: so with a wary and discreet eie we must auoyde their harmes..."
Edward Topsell, The Historie of Foure-Footed Beastes
A little-known health risk: cats breathing in your bed.