How Often to Touch Up Gray Roots and What Sets the Timing

If you use permanent color, plan on touching up gray roots every few weeks. A 2014 dermatology review in Actas Dermo-Sifiliográficas gives 4 to 6 weeks, and a 2015 review in the International Journal of Trichology gives 15 to 30 days. Where you fall in that range depends on how fast your hair grows, how strongly your color contrasts with your gray, and which type of color you use.

This post is part of our guide to ways to cover gray hair.

Why roots show at all

Permanent dye does not wash out. It forms large color molecules inside the hair that cannot escape, so the colored part of each strand stays colored. The problem is the new hair. The 2015 review notes that the white hair you see 10 to 15 days after dyeing is new growth, not faded dye.

That growth can be measured. In a 2004 study of 3,343 scalp hairs from women, white hairs grew 0.38 mm a day and pigmented hairs grew 0.35 mm a day. Here is what those rates add up to:

Time since coloring	New growth at 0.35 mm a day	New growth at 0.38 mm a day
2 weeks	4.9 mm	5.3 mm
4 weeks	9.8 mm	10.6 mm
6 weeks	14.7 mm	16.0 mm

These are averages from one study, and the study also found differences between areas of the scalp. Your own hair may grow faster or slower. The study found that white hairs grew faster than pigmented ones, so if you are mostly gray, your regrowth may be closer to the higher numbers.

Contrast decides when you notice

The same 5 mm of regrowth can be easy or hard to see. It depends on the difference between your color and your gray.

A dark brown or black shade over white regrowth creates a clear band at the part. A lighter shade creates less contrast, so the same amount of growth is harder to see. The American Academy of Dermatology suggests choosing a dye within three shades of your natural color. It also says dyeing darker is usually better than going lighter, because lightening by more than three shades needs stronger peroxide.

For people with a lot of gray, these two points can conflict. A darker shade is usually easier on the hair, but it shows more contrast against white regrowth. A colorist can help you find a shade that balances the two.

Blending softens the contrast in a different way. Lowlights, highlights or a sheer tint leave some gray in the look, so new gray growth stands out less. Our page on gray blending and lowlights explains the options.

The type of color changes the schedule

Each type of color has its own timing:

• Permanent dye lasts until the hair grows out, so only the roots need new color. The 2015 review advises applying the product only to the new growth.
• Demi-permanent dye covers up to 50 percent of gray, according to the 2014 review, and fades after 10 to 15 shampoos, according to the 2015 review. Because the color fades along the whole strand, its timing depends on how often you wash as well as on root growth.
• Semi-permanent dye lasts 6 to 8 shampoos, according to the 2014 review. It softens gray rather than hiding it.
• Gradual color builds in small steps. The FDA, citing one maker's directions for an older progressive dye based on lead acetate, which the FDA no longer allows in hair dyes, described daily use until the shade was reached, usually 2 to 3 weeks, and then use once or twice a week to keep it.
• Temporary root products last until you wash your hair.

Our page on permanent, demi-permanent and semi-permanent dye explains how each type works.

Ways to make the schedule easier

A few habits can reduce how often you need a full session, or make each session gentler:

1. Use temporary cover between sessions. Sprays, powders, sticks and wands put color on the surface of the hair and wash out with shampoo. They can hide the band until your next wash. See root touch-up products.
2. Lower the contrast. A shade closer to your gray, or blending, makes the same regrowth less obvious.
3. Color only the new growth. This follows the 2015 review's advice and spares the rest of the hair from repeated oxidation. A 2018 review in the International Journal of Trichology notes a risk of damage to the hair shaft from oxidation with permanent dyes.

The interval also sets the yearly cost. Our page on how much covering gray costs shows how: every 4 weeks means 13 sessions a year, and every 6 weeks means 8 or 9.

Do not rush the safety steps

Coloring more often does not change the safety rules. Each time:

• Do a skin patch test first. The FDA says to do one every time before you dye your hair, because people can develop sensitivities with repeated exposure.
• Allow time for a reaction to show. The NHS says symptoms can take up to 72 hours to appear.
• Follow the timing on the box. The FDA says not to leave the product on longer than the directions say.
• Wait after other treatments. The FDA says to wait at least 14 days after bleaching, relaxing or perming before you use dye.

Finding your own interval

After your next color session, notice when the band at your roots starts to bother you, and count the days. Use that number as your interval, within the product's directions. The two reviews give 15 days to 6 weeks as a guide for permanent color.

LIUMIQ is developing a gradual color product for gray hair. It is not on sale yet. If you want to follow the work, join the waitlist.