Probiotic skin care was the buzzword of the beauty scene in 2019. Now, Aveeno Hair is introducing the benefits of probiotics and the good-for-you bacteria they harness to the hair world in 2020 with its new Kefir Probiotic Blend Shampoo ($9), which features a particularly unique blend of what we know as drinkable yoghurt (kefir), probiotics, and the line's signature oat.