My guess would be that there may be a lot of loose fibres and instead of tracking them around the house you remove the vast majority from that first wash.
It’s generally good policy to wash new items before using them when possible, particularly things that are going into or onto your body; you don’t know where it’s been.
If it is a printed bath rug it may be to remove excess dyes from the fabric so they do not leach or stain the floor. More so for a bathroom where more moisture is present. Even being polyester (essentially plastic fiber) it can still lose some dye like natural fiber will. If it’s not printed, then I definitely agree with the previous posters.
Other items have wash first before using stickers, like cups. Maybe the instruction writers are Freelancers and they get a lot of use out of this phrase.
Oh yeah. I had a new vinyl tile bathroom installed. So pretty and white. I bought a very cute dark blue little rug set, you know the cut out around the toilet and in front of the sink. Sure as hell, that rug, which I had never laundered, stained that pretty white floor dark blue where the rugs were, and it was not ever coming out. Maybe I should read tags.
If you read about buying good towels, everyone says to wash them with vinegar before use. They are made with a heavy dose of softener-like coating to keep them nice and fluffy on display. If you use them without such a washing, it tends to lock in the coating and they never absorb the way they should. Of course they don’t seem to mention this on any instructions (or perhaps I never read the labels).
How are you going to manage keeping a clean towel in this bathroom? Hopefully, whatever your plan is for that, you can use the same method to clean the new rug.
You should wash everything before you use it. On an episode of House a kid was dying and it turned out to be His mother bought knock-off jeans at a flea market and he wore them without laundering them first and the dye was poisoning him.
tangent: research in the last couple of years indicates that a huge fraction of the plastics going into the ocean from first-world-countries-with-good-garbage-collection-services is --tiny fibers washed from fabric.
And although the fabric industry is not permitted to wash dyes down river anymore, there are no restrictions on what the fabric does after they sell it to you.
So of course they don’t wash it before they sell it to you…
I had a part-time temp job working at an At Home store. One of the tasks I did a couple of days was to sort/reorganize/neaten the rug displays. They had shelves of rugs of various types and colors, and some vague “similar color” concept, plus specific types of rugs might get spread into more than one pile. It was time consuming to approach it the way me and another guy started, which was very thorough.
Anyway, after handling these rugs for about 4 hours each on two different days, I noticed (a) that a lot of them smelled like vinegar or other chemicals, and (b) that I got some kind of red irritation of my skin from the chemicals. It looked like sunburn, but wasn’t painful, just reddish skin. I think you probably should wash the rug to get any chemical residue out.
My husband follows this policy. I follow the policy of “washing? feh. I’m touching things that I don’t know where they’ve been ALL DAY!”
After following our respective policies for 40+ years we have both had the same number of problems from residual chemicals on new products - ie, zero.
On the other hand, some people’s skin is more sensitive (and to different things) than others. And I see harmonicamoon has fixed her immediate problem in any case
I have to say that I have never washed any of my new polyester bathrugs before use in 'lo these many years upon the earth and I’ve never had an issue. There have been many rugs (because I like rugs on my tile, that’s why). I think you’ll be fine. Wash it someday with your towels. Don’t worry about it now.
It will probably be more slippery, i.e. more likely to slip on the floor, owing to something put on it in the manufacturing process. If you don’t wash it, step carefully.