Nails
What Your Nails Are Recording
A nail is a slow, physical diary of the months behind you. Learning to read it is useful.
Published 2026-09-12 · 8 minute read · The Gelagen Journal
Of everything on a human body, a fingernail is the most legible. It grows at a steady, measurable rate, it does not remodel itself once it has been made, and it cannot be talked out of what it is showing you by good lighting or a good mood. It is a physical diary of the months behind you.
What A Nail Is Made Of
The nail plate is dead, compacted keratin, produced by a living tissue called the matrix that sits underneath the skin behind your cuticle. Everything visible was manufactured there and pushed forward. That is the crucial fact: you cannot improve a nail that already exists, only the section that has not been built yet.
The pale half-moon at the base, the lunula, is the visible front edge of that matrix. The cuticle is a seal protecting it. Pushing a cuticle back aggressively is one of the few genuinely damaging things people do to nails on purpose, because it exposes the factory.
The Timeline
Fingernails grow roughly three millimetres a month, so a full fingernail takes about six months to replace itself entirely. Toenails are slower, often twelve to eighteen months. Growth is faster on the dominant hand, faster in summer than in winter, faster in youth, and slower during illness.
Which means: whatever your nail tip shows, it was decided last winter. Whatever changes you have made recently will appear near the cuticle first and will not reach the end of the nail for months. This is exactly why our ninety day timeline asks people to look at new growth rather than at the whole nail.
What The Marks Mean
| What you see | What it usually is |
|---|---|
| White spots or lines | Almost always minor trauma to the matrix weeks earlier - a knock you have forgotten. The old story about calcium or zinc deficiency is mostly folklore. |
| Vertical ridges running to the tip | Extremely common and usually just age. They become more pronounced from about thirty-five onwards and mean very little on their own. |
| Horizontal grooves across the nail | Beau's lines. They mark a period when the matrix paused - a serious illness, a high fever, chemotherapy, sometimes a severe episode of stress. Their distance from the cuticle dates the event. |
| Splitting into layers at the tip | Onychoschizia, and the commonest single cause is repeated wetting and drying. Detergent, washing up, and hand sanitiser. |
| Spoon-shaped nails | Koilonychia. Worth mentioning to a doctor, since it has a real association with iron deficiency. |
| A dark line running lengthways | Usually benign, particularly in darker skin where it is common. A new one, a widening one, or one spreading onto the surrounding skin needs a doctor promptly. |
| Thickened, crumbling, discoloured nails | Frequently a fungal infection, and it needs a diagnosis and treatment rather than a supplement. |
Why Nails Split
The single biggest cause is water. A nail plate absorbs water, swells, and then contracts as it dries. Doing that repeatedly - washing up, frequent hand washing, sanitiser several times an hour - fatigues the layers and they separate. This is why nail brittleness so often tracks a job rather than a diet.
The rest of the list: acetone-based remover, gel and acrylic removal done impatiently, using nails as tools, and very cold dry air.
What Actually Helps
Gloves for wet work. Unglamorous and the most effective single intervention available.
Moisturise the nail, not only the hand. Any ordinary hand cream worked into the nail and the skin around it, several times a day, reduces the swelling and shrinking cycle.
Keep them shorter for a while. Less lever arm, fewer catches, less splitting.
File in one direction. Sawing back and forth separates the layers at the edge, which is where splits begin.
Give them a break from gels. The damage is rarely the product and usually the removal.
Where Nutrition Fits
Nails are keratin, and keratin is assembled from amino acids by enzymes that need cofactors. Biotin is the nutrient with the clearest human evidence here: small studies in the late 1980s and 1990s found measurable increases in nail plate thickness in people with brittle nails, over several months.
Those studies were small and uncontrolled by modern standards, and they were in people who already had brittle nails. That is the honest framing: a plausible effect where a shortfall exists, over months rather than weeks, and not a transformation.
Iron and zinc status both matter too, and both are worth testing rather than guessing if your nails have changed noticeably and stayed changed.
When To See A Doctor
- A new dark stripe, or one that is widening or spreading onto the skin
- A nail separating from its bed without an injury to explain it
- Sudden thickening, crumbling or a colour change
- Redness, swelling or pain around the nail fold
- Spoon-shaped nails, particularly alongside fatigue
- Nail changes on several nails at once with no obvious cause
Nails are one of the places general health shows early, which is a good reason to look at them occasionally and a bad reason to diagnose yourself from a chart on the internet, this one included.
Questions
Quick Answers
How fast do nails grow?
Fingernails around three millimetres a month, so about six months to replace a whole nail. Toenails take considerably longer.
Do white spots mean a deficiency?
Usually not. Most are minor trauma to the matrix weeks earlier, and the deficiency story is largely folklore.
Does nail polish damage nails?
Polish itself is fairly benign. Acetone remover and impatient gel removal cause most of the damage attributed to it.
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