i always figured that a regular rashguard had some spf blocking abilities and that the ones that said they had spf blocking ability had something extra, besides 15 more bucks out of your pocket.
but i went to my local shop and they said they where all the same.
whats the deal is there a difference between spf rash guards and ones that dont say they are.
I really think all rashguards have spf protection also but on oniell i think they say that on all of their rash guards I dont think others do
It’s a hard one to answer when it comes to our health, but essentially all items of clothing have some degree of SPF whether we mean them to or not (except maybe your village people style mesh vest 
Even a T-Shirt has some level of sun protection, it’s just that it is not rated (SPF rating) so it is hard to know exactly how good or bad being out in the sun with it would be. You need to get a doctor’s opinion on this but it would be safe to say that even a 2mm wetsuit would have total SPF, a 2mm or 1mm wetsuit vest probably similar but once you get down to the fabric in a rash vest, you would get some variance in the level of protection depending on the thickness, type and manufacturer of the fabric.
Although all rash vests would give some sun protection, the ones with an SPF rating will have been through the rigor of SPF testing and therefore you have a feel for what you are dealing with. I wouldn’t go as far as to say that they are all the same.
Hope this helps
All offer some degree of protection, BUT, the tighter (and in lesser degree, heavier) the weave, the more protection afforded. Pull the prospective rashie taut over your hand to approximate stretch when worn-if you can see hand skin, both SPF and wind resistance are LOW. I consider “magic/miracle” treated fabric to be marketing BS. Heh, heh, the ULTIMATE in protection is your favorite nylon
windbreaker…a leather bomber jacket, a peacoat, a skijacket, a minkcoat…
yeah i agree with the fact that everything that you waer has some form of uv protection. but when you wear that white t-shirt out in the water it doesnt really help much. i thought that there had to be some kind of difference between regualr rashguards and the uv kind
thanks for the suggestions lacronic, this weekend i will be streching rashguards over my hand at my local shop to test uv protection. i will update you on my findings