KRT1 was used to semi-quantify the protein content per samples: the number of MS-identified KRT1 peptides per sample is given in Table S1; between 22 and 62 KRT1 peptides in samples derived from acne-affected areas (acne-A1) and 28 to 57 peptides in those from nasal areas (nose-A1) could be identified. Here, KRT1 is linked to acne.