# DNAm Skin & Blood clock (Horvath 2018)

The DNAm Skin & Blood clock was published by Horvath and colleagues in 2018. It estimates your epigenetic age from 391 CpG sites. Those sites were picked from methylation arrays run on skin fibroblasts and blood. It was built to fix a known flaw. The original 2013 Horvath clock kept under-estimating age in keratinocytes and fibroblasts. Those are the very skin cells at the heart of lab studies of reprogramming and rejuvenation. This clock was trained on a tissue you can easily sample. So it is often used as a readout in partial-reprogramming experiments, next to the multi-tissue Horvath clock.

## Sources

- Horvath S, Oshima J, Martin GM, Lu AT, Quach A, Cohen H, Felton S, Matsuyama M, Lowe D, Kabacik S, Wilson JG, Reiner AP, Maierhofer A, Flunkert J, Aviv A, Hou L, Baccarelli AA, Li Y, Stewart JD, Whitsel EA, Ferrucci L, Perl S, Raj K. (2018). Epigenetic clock for skin and blood cells applied to Hutchinson Gilford Progeria Syndrome and ex vivo studies. Aging (Albany NY). https://doi.org/10.18632/aging.101508

---

_Canonical: https://longevity-switzerland.com/en/glossary/skin-blood-clock · Part of Longevity Cities · Updated 2026-06-22_