Root Touch-Up Products for Gray Hair

Root touch-up products hide gray regrowth between full color sessions. Many are temporary: sprays, powders, sticks and mascara-style wands put color on the outside of the hair, and it comes off when you shampoo. Root kits are a different product. They use dye that you mix with a developer, so they last until the hair grows out and need the same allergy test as a full box of dye.

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

Why roots show so soon

Permanent dye does not wash out, but hair keeps growing. A 2015 review in the International Journal of Trichology says the white hair that appears 10 to 15 days after dyeing is new growth, not faded color.

The amount is small at first, but it grows every day. In a 2004 study of scalp hair from women, white hairs grew 0.38 mm a day and pigmented hairs 0.35 mm a day. At those rates, two weeks adds 4.9 to 5.3 mm of new growth, and four weeks adds 9.8 to 10.6 mm. Against dark color, that band can be easy to see.

Root products cover the roots until the next full session. A 2014 review in Actas Dermo-Sifiliográficas says permanent dyeing must be repeated every 4 to 6 weeks to cover new growth, and the 2015 review suggests 15 to 30 days.

Two kinds of root product

Products sold for roots fall into two groups, and they work in very different ways:

• Temporary cover-ups put color on the surface of the hair. They wash out.
• Root kits are smaller versions of oxidative dye kits, the kind you mix with a developer. They change the color inside the hair and do not wash out. Check the box to see whether a kit is permanent or demi-permanent.

How temporary root color works

The 2014 review explains how temporary hair dyes work. The dye molecules are large, so they cannot get inside the hair. They stay on the surface of the cuticle, the outer layer of the strand. In these products, the dye is bonded to a positively charged polymer, which helps it cling to the hair. The bond is weak, so shampoo removes it easily.

Other reviews agree. A 2018 review in the International Journal of Trichology says temporary dyes do not penetrate the cuticle and wash out with shampooing. A 2009 review in the Journal of Emergencies, Trauma and Shock describes them as water-soluble dyes that withstand only one shampoo.

The 2014 review lists the forms these products come in, including sprays, lotions, foams, lacquers and shampoos. Sprays and lacquers stay in place until the hair is washed, while shampoo-style products are rinsed out. The review also warns that temporary color products easily stain the hair and scalp.

Common forms

Temporary root products come in a few shapes. Each one puts color on the surface of the hair in a slightly different way:

• Sprays release a fine mist of color and can cover a wide area, such as the part line or the hairline.
• Powders are brushed or dabbed onto the roots.
• Sticks and crayons are drawn along the part or the temples.
• Mascara-style wands are combed through small sections of hair.

The label tells you how to apply the product and how to remove it. Because these products can stain skin, keep them off your scalp and face as much as you can, and try the product on a small area first.

How long temporary color lasts

The 2014 review says temporary dye "usually remains in place for a week and is easily removed by shampooing." In practice, the color lasts until you wash your hair, so how often you reapply depends on how often you wash. Temporary color stays on the surface and does not change the color inside the hair.

Root kits: oxidative dye in a small box

A root kit uses oxidative dye. With permanent dye, the 2014 review explains, the developer and an alkaline agent carry the dye into the cortex, the inner part of the strand. There, the dye forms color molecules that are too large to wash out. That is why the result from a permanent root kit lasts until the hair grows out.

Because the chemistry is the same as full permanent dye, the same safety rules apply:

• The NHS says PPD, the main cause of hair dye allergy, is found in many permanent dyes.
• The FDA says to do a skin patch test every time before you dye your hair, and not to leave the product on longer than the directions say.
• The 2015 review advises applying root color only to the new growth, not over hair that is already colored.
• The FDA says to wait at least 14 days after bleaching, relaxing or perming before you use dye.

Side by side

Product	Where the color sits	How long it lasts	Allergy check
Spray, powder, stick or wand (temporary)	On the surface of the hair	Until you wash your hair	Follow the label, and stop if your skin reacts
Root kit (oxidative dye)	Inside the hair, in the cortex	Until the hair grows out (permanent kits)	A skin patch test every time, as the FDA advises

Safety for every root product

Temporary colors are not free of risk. The 2014 review mentions sporadic reports of allergic contact dermatitis from some ingredients in temporary hair dyes, such as quinine. The American Academy of Dermatology says that a rash, redness, swelling, burning or itching after using hair color means you are having an allergic reaction.

The FDA uses the term "coal-tar hair dyes" for synthetic hair dyes, and it says this group includes permanent, semi-permanent and temporary dyes. Under US law, the FDA cannot act against a coal-tar hair dye because of a harmful ingredient, as long as its label has a special caution statement and it comes with directions for a skin test. That makes the label directions important. If your root product carries the caution statement, do the test it describes.

Keep every root product away from your eyes. The FDA says hair dyes have caused eye injuries, including blindness, when used in the eye area, and that no color additives are approved for dyeing the eyebrows or eyelashes. It also says not to dye your hair if your scalp is irritated, sunburned or damaged. Our page on hair dye allergies and patch tests explains the symptoms to watch for.

When a touch-up makes sense

Root products are most useful in a few situations:

• Between permanent color sessions, to extend the time until your next full appointment.
• Before an event, when you need the roots covered for a day or two.
• During blending or grow-out, to soften a line while the colored ends grow out. See gray blending and lowlights.

If you are coloring at home, our post on covering gray at home for the first time covers the basics, and how often to touch up gray roots explains the timing. For the dye types themselves, see permanent, demi-permanent and semi-permanent dye.

LIUMIQ is developing a gradual color product for gray hair. It is not available to buy. Join the waitlist if you want updates on the work.