Shereene IdrissBoard Certified Derm, Founder and Chief Nerd

Did you know your nails are a timeline of your health?

6 Jul 2026 · 0 min

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0:24

Dermatologist Shereene Idriss explains how nails work like a health timeline. Horizontal ridges called Beau's lines appear after illness or stress, and since nails grow about 3 mm per month, you can measure the ridge's distance from the base to figure out when you got sick.

Your nail plate is like a timeline of your life. Think of it as like the rings on a tree. When you see those Beau's lines, you can measure how long ago that incident happened because your nail grows at about 3 millimeters or so a month. So wherever that ridge happens, right, 3 millimeters is probably like a month, 6 millimeters is probably 2 months, 9 millimeters is probably 3 months, and so forth. So it's kind of a cool way to tell time.