Although some clocks based on DNA methylation present better results, we must highlight that: (1) Epidermal or dermis samples could present better accuracy than whole skin biopsy [34]; (2) In addition, upper layers of keratinocytes do not have nuclear DNA so the epigenetic clock based on the use of DNA methylation is not a good option for skin’s clock [11, 35]; (3) In some common pathologies of skin associated with accelerated aging, such as psoriasis, methylation-based clocks have not shown good prediction [11, 35]. This evidence concerns the gene CLOCK and psoriasis.