What fibre construction are they made from?
Ideally I like Scotchgard from 3M but I've heard good reports about Prochem Fabric Seal which I believe is 'spirit based' and ideal for upholstered fabrics although you'd have to wear a mask and have a well ventilated area.
There are other protectors on the market some good some not so but an idea of the fabric would be a good start.
Shaun