Synthetic Dyes and Coal Tar Colors in Cosmetics

Key takeaways

• Most synthetic cosmetic colors are made from petroleum; they were historically derived from coal tar, which gave them their old name.
• In the US, many synthetic colors must be batch certified by the FDA and are approved only for specific uses.
• Some dyes can cause skin reactions in sensitive people, and coal tar hair dyes have their own special rules.
• Colors serve mostly appearance, so leaving them out is an easy way to shorten an ingredient list.

Walk down a personal care aisle and you will see blue mouthwash, pink body wash, green shampoo, and bright orange soap. Very little of that color comes from the ingredients that clean or moisturize. It is added purely for appearance, and in most mass market products it comes from synthetic dyes. These colorants are among the more heavily regulated ingredients in US cosmetics, which is reassuring in some ways. Still, they are worth understanding, especially for people with sensitive skin or those who prefer to keep their routine as simple as possible.

What are synthetic dyes?

Synthetic dyes are color additives made through chemical synthesis. In the 1800s, chemists discovered they could make vivid dyes from coal tar, a thick by-product of turning coal into coke and gas. The name "coal tar colors" stuck. Today most of these colors are made from petroleum derived starting materials rather than coal tar, but the term still appears in discussions and some regulations.

Synthetic colors come in two main forms. Dyes dissolve in water or oil and tint the whole product. Lakes are dyes bonded to a mineral base such as aluminum hydroxide, which makes them insoluble. Lakes are used in makeup like lipstick, eyeshadow, and blush, where color should stay put rather than bleed.

How the FDA regulates color additives

Color additives are one of the few cosmetic ingredient categories that require FDA approval before use. Under the Federal Food, Drug, and Cosmetic Act, every color additive must be approved for its intended use, and many synthetic colors must also be batch certified, meaning each batch is tested by the FDA for composition and impurities, including limits on heavy metals such as lead and arsenic.

Approval is use specific. A color may be allowed in products applied to the skin but not near the eyes, or allowed in cosmetics but not in food. The FDA states that using a color additive in a way it has not been approved for makes a cosmetic adulterated. Colors not approved for the eye area are a particular concern, and the FDA has issued warnings about imported products using unapproved colors.

There is one notable exception. Coal tar hair dyes are exempt from the color additive approval requirement, provided the label carries a caution statement and instructions for a preliminary patch test. That exemption dates back to the original 1938 law. Our article on PPD and resorcinol in hair dye covers those products in detail.

Where synthetic dyes show up

• Colored soaps, body washes, and shampoos
• Mouthwash and toothpaste
• Lipstick, lip gloss, blush, and eyeshadow
• Bath bombs and bubble baths
• Nail polish
• Products marketed to children, which are often brightly colored

Names on the label

In the US, certified colors are listed with a prefix and number:

• FD&C colors, approved for foods, drugs, and cosmetics, such as FD&C Red No. 40, FD&C Yellow No. 5, and FD&C Blue No. 1
• D&C colors, approved for drugs and cosmetics, such as D&C Red No. 27 or D&C Green No. 5
• Ext. D&C colors, approved only for externally applied drugs and cosmetics
• Lake after a color name, such as Red 7 Lake

International labels use Color Index (CI) numbers, a five digit code. For example, CI 16035 corresponds to Red 40, CI 19140 to Yellow 5, and CI 42090 to Blue 1. Mineral pigments such as iron oxides (CI 77491, 77492, 77499) and titanium dioxide (CI 77891) also use CI numbers, so a CI code alone does not tell you a color is synthetic. Our guide to reading ingredient labels explains these systems.

What the research says

Skin reactions

Most people use products with certified colors without any problem. Some dyes can cause allergic or irritant reactions in sensitive people, and certain colors have been associated with contact dermatitis around the lips and eyes. Tartrazine (FD&C Yellow No. 5) is known to cause reactions such as hives in a small number of people, which is why US rules require it to be declared by name in foods and drugs.

Regulatory history

The history of color additives includes several colors that were later removed. FD&C Red No. 3 is the best known example. Its approval for use in cosmetics and externally applied drugs was revoked in 1990 after studies found it caused thyroid tumors in male rats, and in 2025 the FDA also revoked its authorization in food and ingested drugs. The FDA has also announced plans to phase out petroleum based synthetic dyes from the US food supply, a separate effort focused on what we eat.

These decisions reflect the strict Delaney Clause in US law, which prohibits approving a color additive found to cause cancer in humans or animals, regardless of dose. Regulators note that the tumors seen with Red No. 3 in rats arose through a mechanism thought to be specific to rats, so the risk to people from typical exposure is considered low. The episode is still a reminder that approvals can change as science develops.

Impurities

Batch certification limits impurities, including heavy metals, in certified colors. Uncertified or imported products may not meet those limits. Our article on lead, mercury, and heavy metals in cosmetics explains why that matters, especially for lip products.

Who should be most careful

• People with sensitive skin or eczema, for whom any nonessential additive is one more possible trigger. See our guide to sensitive skin irritants.
• People with a known sensitivity to tartrazine or other dyes.
• Parents, since brightly colored products are heavily marketed to children. Our article on non toxic skin care for kids offers simpler options.
• Anyone buying cosmetics from unregulated sources, where unapproved colors or contaminants are more likely.

How to spot and avoid synthetic dyes

1. Look for FD&C, D&C, and Ext. D&C on US labels, and check CI numbers on international ones.
2. Ask whether color adds anything. In soaps, shampoos, and lotions, it usually does not change how the product works.
3. Prefer mineral or plant based colorants where color matters, such as iron oxides, clays, or botanicals like annatto or alkanet root, while remembering that natural colorants can cause reactions too.
4. Buy from reputable sources that sell products compliant with US color rules.
5. Read the whole label. Brightly colored products are often also heavily scented. Our article on synthetic fragrance explains what that word can hide.

The color of the ingredients themselves

At Lucky Lady Ranch we let our ingredients speak for themselves. Our Body Bar takes its creamy color from the oils and butters it is made with, and our Epsom Sea Salt Bath Soak gets its soft tone from salts and magnetic clay. We do not add synthetic dyes to make a product look a certain way. A bar that looks like what it is made of feels honest to us, and leaving out what you do not need is one of the simplest ways to care for your skin.

From the ranch

Made in small batches, without the ingredients discussed above.

Questions people ask

What are coal tar dyes in cosmetics?

Coal tar dyes are synthetic colors originally made from coal tar. Today most are made from petroleum based materials. In the US they are typically listed as FD&C or D&C colors and must be approved and often batch certified by the FDA.

Are synthetic dyes in cosmetics safe?

Certified colors are tested for impurities and approved for specific uses, and most people tolerate them well. Some dyes can cause skin reactions in sensitive people, and approvals have changed over time as research developed.

What does CI mean on an ingredient label?

CI stands for Color Index. It is a five digit number used internationally to identify colorants, both synthetic dyes and mineral pigments such as iron oxides.

Why was Red No. 3 banned?

Red No. 3 caused thyroid tumors in male rats. Its use in cosmetics was revoked in 1990, and in 2025 the FDA revoked its use in food and ingested drugs under the Delaney Clause.

What is a lake in makeup?

A lake is a dye bonded to a mineral base, often aluminum hydroxide, which makes the color insoluble. Lakes are common in lipstick, blush, and eyeshadow.

Sources and further reading

1. US Food and Drug Administration (FDA), Color Additives Permitted for Use in Cosmetics
2. US Food and Drug Administration (FDA), Color Additives and Cosmetics: Fact Sheet
3. US Food and Drug Administration (FDA), FD&C Red No. 3 Authorization Revoked in Food and Ingested Drugs (2025)
4. Code of Federal Regulations, Title 21, Parts 73, 74, and 82 (Color Additives)
5. Color Index International (CI), colorant reference database

This guide is for general education and is not medical advice. If you have a skin condition, allergy, or are pregnant or nursing, talk with your doctor or a board certified dermatologist about the products that are right for you.