Sweep pretty much only runs when she's loose in our fenced backyard and wearing only her tag collar, so I can't say for sure, but there's been no chafing in her three daily walks for the year or so we've been using the harness. The part that goes under the "armpits" is velvet, so that helps! (I see Cynthia just mentioned that too as I was typing this!) BTW, Sweep's tag collar is also velvet and all her neck fur grew back once we switched to it. We got it on Etsy. We also have and can recommend the 2Hounds velvet jingle-free tag collar. (Sweep has a ridiculous collar collection!)