Gradual Hair Color Explained

Gradual hair color, also called progressive color, darkens gray hair a little each time you apply it, so the change builds over days or weeks instead of in one session. The older products in this category used metal salts, most often lead acetate, which react with the sulfur in hair. In the United States, lead acetate has not been allowed in hair dye since January 6, 2022, while bismuth citrate and henna remain approved color additives for hair.

This page describes the category as a whole. It is part of our guide to ways to cover gray hair.

What "gradual" means

In a 2021 notice, the FDA described progressive hair dyes as products that, "when applied to gray hair, gradually change the color with repeated applications." The notice gave an example from one maker's directions for a lead acetate product: apply it daily until you reach the shade you want, which usually took 2 to 3 weeks, then once or twice a week to keep the color.

That pattern defines the category. Each use adds a small amount of color. You stop the daily routine when you like the result, and you keep it with less frequent use. Permanent dye is different: the full change happens in one session.

Medical reviews group these products by what they are made of. A 2009 review in the Journal of Emergencies, Trauma and Shock lists "gradual hair coloring" as its own category, made with metallic dyes such as salts of lead, bismuth or silver. A 2014 review in Actas Dermo-Sifiliográficas describes mineral or metallic dyes as products that need daily use, change hair color gradually, and may last for weeks or months.

How the classic metal-salt products worked

Hair keratin, the protein in the hair shaft, contains sulfur. The classic gradual dyes used that sulfur. The 2009 review explains that progressive dyes change hair "from light straw color to almost black" by reacting with the sulfur of hair keratin and by oxidizing on the hair surface.

A 2022 paper in the journal Sensors gives more detail. When the metal salt meets the sulfur in keratin, a mixture of metal oxides and insoluble metal sulfide forms. That mixture is what slowly darkens the white strands. Because each application adds only a little, the shade changes in small steps.

The 2014 review adds two cautions about metallic dyes made with silver nitrate or lead salts. It calls them potentially toxic, and it says they are incompatible with hydrogen peroxide, the developer used in permanent dye. If you have used a gradual product and plan to switch to permanent dye, tell your colorist.

Lead acetate: approved in 1980, repealed in 2018 to 2022

In the United States, lead acetate was approved for this use from 1980 until 2022. The 2009 review names it as the active ingredient in progressive dye products and says bismuth citrate was used "to a much lesser extent."

The FDA first approved lead acetate on October 31, 1980, for coloring hair on the scalp, at up to 0.6 percent lead. In 2017, a group of health and environmental organizations asked the FDA to repeal that approval. The FDA agreed. In a final rule published on October 31, 2018, it said new data showed there was no longer a reasonable certainty of no harm from this use. Among its reasons, the FDA said it could not identify a safe level of lead exposure, and that the skin absorption study it had relied on in 1980 underestimated how much lead passes through the skin.

A company that made lead acetate hair dyes objected. Under US law, the objections put the rule on hold, and the FDA restored the old listing on April 1, 2019, while it reviewed them. In October 2021, the FDA denied the objections. The repeal took effect on January 6, 2022, and the FDA gave companies 12 months to use up existing stock and reformulate.

Health Canada says lead acetate is no longer acceptable in cosmetic products in Canada. Our post on what happened to progressive hair dyes covers each step of the US timeline.

Bismuth citrate

Bismuth citrate is a salt of bismuth and citric acid. Under the US color additive rules (21 CFR 73.2110), first published in 1978, it may be used in cosmetics that color hair on the scalp at up to 2.0 percent. It may not be used to color eyelashes, eyebrows or hair on other parts of the body. Its label must say:

Keep this product out of children's reach. Do not use on cut or abraded scalp. Do not use to color eyelashes, eyebrows, or hair on parts of the body other than the scalp. Wash hands thoroughly after each use.

When the FDA repealed lead acetate, it noted that bismuth citrate was already being used as an alternative in hair dye products sold in the United States and other countries.

Henna

The FDA also lists henna, from the Lawsonia plant, as a color additive approved for hair. It groups henna with bismuth citrate as ingredients "used in hair dyes that may darken hair gradually with repeated applications."

Do not confuse henna with "black henna." The FDA warns that temporary tattoos sold as "black henna" contain PPD, a common hair dye allergen, and may increase your risk of allergy to hair dyes. Our page on hair dye allergies and patch tests explains that risk.

How gradual color compares with other dye types

Feature	Gradual (classic metal salt)	Permanent dye	Semi-permanent dye
How the color builds	A small change with each use	The full change in one session	The full change in one session, then fades
What happens in the hair	Metal salts react with sulfur in keratin and form dark sulfides and oxides	Dye precursors react with peroxide and form large color molecules in the cortex	Small, ready-made dye molecules enter the outer layers
How long it lasts	Needs repeated use to keep the shade	Until the hair grows out	4 to 8 shampoos, depending on the source
Typical routine	Daily at first, then once or twice a week (one maker's directions, cited by the FDA)	Roots every 4 to 6 weeks (2014 review)	Reapply as it fades

More detail on the last two columns is on our page about permanent, demi-permanent and semi-permanent dye.

Reading the label on a gradual product

Products sold as "gradual" do not all use the same ingredients. Before you buy one, check a few things:

• The ingredient list. In the United States, lead acetate should no longer appear. Bismuth citrate or henna may.
• The warnings. Products with bismuth citrate must carry the warning above. Follow it exactly.
• The directions. They tell you how often to apply the product and how to keep the shade once you reach it.
• Allergy testing. The FDA advises a patch test on your skin every time before you dye your hair.
• Where you use it. The FDA says to keep hair dyes away from your eyes and not to dye your eyebrows or eyelashes.

A gradual product will not cover regrowth overnight. If you need a quick fix while the color builds, root touch-up products can hide the roots until your next wash.

What gradual color does not do

Gradual color is still hair color. It adds color to the hair shaft. It does not change how the hair follicle makes pigment, so gray hair that grows in later is still gray. For what science says about gray hair regaining its color, see can gray hair turn back to color.

LIUMIQ is working on a gradual color product for gray hair. It is still in development and is not for sale. You can join the waitlist to follow its progress.