Smaller hair bulbs were reported at the postnatal HF morphogenesis, and premature entry into catagen was postulated to be the underlying cause.10 Similar phenotype was reported by Lee et al, in which smaller hair bulb of Notch1‐deficient HFs was attributed to lower mitotic rates mediated by paracrine inhibition of IGF signaling in the Mx through DP‐derived IGFBP3.11 However, Hes1 expression was unaltered in Notch1‐deficient HFs, nor did we observe any difference in Igfbp3 expression as well as characteristics and inductive ability between control and Hes1eKO DPs. Here, IGFBP3 is linked to hydrops fetalis.