Hi, Not exactly sure but I would turn down the Glossy Reflectivity on the hair in the Iray Surfaces and/or turn up the Glossy Roughness. You could also change the Glossy Weight but I find that can end up with dull looking hair. If that does not work, I would next look to see if the Top Coat Weight is set above 0 and lower the Reflectivity and increase the Top Coat Roughness. Not sure that will help, I hope it does, but that is where I would look first.