How to remove spew from leather, this is the animal fat that leaks to the leather surface. One can determine if its spew by using a hair dryer and the mark will disappear.
I've done some reading up on spew before, but never actually dealt with it! There are quite a few spew remover products available. They penetrate the surface of the leather, and stop it coming back.
https://www.furnitureclinic.co.uk/Spew_Remover.php 
