It is a good idea to wash all the fleece lined pads that will go next to the horse’s back before you first use them.  There are two reasons for this:
The wool on these pads has been shorn from the sheep and then knitted onto a cotton backing.  Because it has been through this manufacturing process it is a good idea to wash it as instructed to remove any chemical residue that may be there.Because of this process, the individual fibres will not all be lying in the same direction as they would if they were still attached to a skin.  So, the cuticles on each hair shaft will not all be lying in the same direction.  This can make the fibres feel rather ‘rough’.  Washing as instructed, particularly using the cup of white vinegar in the final rinse, will soften the fibres so that they feel better for the horse.