What is red number 3 dye made of?

January 12, 2026 •

4 min read

Recent FDA actions led to the eventual ban of Red No. 3 from food and ingested drugs in the U.S. after more than three decades of debate. Red No. 3 dye, also known as erythrosine, is a synthetic, chemical dye derived from petroleum. The dye was originally created in 1876 and has been used to impart a bright, cherry-red color to a variety of products.

Quick Summary

Red No. 3, or erythrosine, is a synthetic dye derived from petroleum that imparts a bright, cherry-red color. It is produced through the chemical synthesis of fluorescein, which is then iodinated. Concerns over its safety, including links to thyroid cancer in animal studies, led to its ban in cosmetics in 1990 and eventually in foods and ingested drugs in the U.S. in early 2025. Manufacturers are now replacing it with natural alternatives.

Key Points

Petroleum Derivative: Red No. 3, also known as erythrosine, is a synthetic dye created from petroleum-based compounds.
Synthesized from Fluorescein: The dye is manufactured through a chemical process that involves synthesizing fluorescein from resorcinol and phthalic anhydride, followed by iodination.
History of Controversy: Concerns over Red No. 3’s safety have existed for decades, notably its link to thyroid cancer in animal studies dating back to the 1980s.
Regulatory Paradox: The FDA banned Red No. 3 from cosmetics and topical drugs in 1990 due to cancer links but delayed banning it from food and ingested drugs until 2025.
Recent U.S. Ban: In January 2025, the FDA officially banned the use of Red No. 3 in food and ingested drugs, citing the long-standing animal study evidence and complying with the Delaney Clause.
Natural Replacements: As manufacturers reformulate products, natural alternatives like beet juice, purple sweet potato extract, and carmine are being used to replace the synthetic red dye.
Ingredient Label Awareness: Consumers should continue to check labels for "FD&C Red No. 3" or "E127" until manufacturers complete product reformulation in 2027 and 2028.

The Chemical Composition of Red No. 3

Red No. 3 is a synthetic dye with the chemical name erythrosine. It is an organoiodine compound, specifically a derivative of fluorescein, and its chemical formula is C20H6I4Na2O5. The name 'erythrosine' comes from the Greek word 'eruthrós' for red, and it is also identified as E127 internationally. The key components of the dye are fluorescein and iodine, with the final product being the disodium salt of 2,4,5,7-tetraiodofluorescein.

The Manufacturing Process

Red No. 3 is manufactured through a specific chemical process that starts with petroleum-based compounds.

Step 1: Creation of Fluorescein: The process begins with the synthesis of fluorescein from resorcinol and phthalic anhydride. This initial step produces fluorescein, a fluorescent dye that acts as a precursor for erythrosine.
Step 2: Iodination: The fluorescein is then subjected to an iodination reaction. In this step, four iodine atoms are added to the fluorescein molecule, which is crucial for achieving the vibrant pink-red color that characterizes Red No. 3. This is a key reason for the dye's regulatory scrutiny, as iodine compounds can affect thyroid function.
Step 3: Salt Formation: The final red dye is converted into a disodium salt. This makes the dye water-soluble and suitable for use in various products.

History and Regulatory Action

Red No. 3 has a long and controversial history. Swiss chemist Karl Kussmaul first developed the dye in 1876, and it was commercialized shortly after for dyeing silk and wool. It was approved for use in U.S. food products in 1907.

The Path to the 2025 FDA Ban

Animal Studies (1980s): Initial animal studies in the 1980s linked high doses of Red No. 3 to thyroid cancer in male rats.
Cosmetics Ban (1990): Based on the findings, the FDA banned the use of Red No. 3 in cosmetics and externally applied drugs in 1990 under the Delaney Clause. This created a regulatory paradox, as it was deemed unsafe for topical use but remained legal for ingestion.
Delayed Action: Despite promising to ban it from food, the FDA took no further action for decades.
Petitions and State Action: Petitions from advocacy groups like the Center for Science in the Public Interest (CSPI) in 2022 and state-level bans, such as California's in 2023, put pressure on the FDA.
Federal Ban (2025): The FDA finally revoked the authorization for Red No. 3 in food and ingested drugs in January 2025, with manufacturers given until January 2027 or 2028 to reformulate products.

Comparison of Red Dyes: No. 3 vs. No. 40


Feature	Red No. 3 (Erythrosine)	Red No. 40 (Allura Red)
Origin	Synthetic, petroleum-based	Synthetic, petroleum-based
Primary Color	Bright pink-red	Crimson
Carcinogenicity	Linked to thyroid cancer in rats	Less pronounced cancer risk than Red No. 3, but contains carcinogens like p-Cresidine
Other Health Concerns	Thyroid hormone disruption, potential neurotoxicity	Associated with hyperactivity in children
Regulatory Status (U.S.)	Banned in food and ingested drugs as of January 2025	Still widely approved and used in food and drugs
International Status	Restricted or banned in many countries (e.g., EU)	Restricted or banned in some countries (e.g., Iceland, Norway); often requires warning labels (e.g., EU)

Safe and Natural Alternatives

Following the ban, many manufacturers have turned to natural sources for red coloring. These alternatives are often derived from fruits, vegetables, and other natural sources.

Beet Juice: A common and effective natural colorant used to create red hues in products like ice cream and fruit pops.
Purple Sweet Potato Extract: Provides rich red and purple tones, offering a versatile plant-based option.
Red Cabbage Extract: Another plant-based source that can create red tones in food.
Carmine: A dye derived from the cochineal insect. While natural, it is not vegan and poses potential allergen concerns, but is a common replacement for Red No. 3.
Radish Extract: Used by some suppliers to create red colors.

Conclusion

In summary, what is red number 3 dye made of is a synthetic substance derived from petroleum through a process that involves iodinating fluorescein. Its chemical composition, specifically the presence of iodine, has been a central point of concern regarding potential health risks. The dye's long history includes a regulatory paradox where it was banned from cosmetics due to cancer links but remained in the food supply for over three decades. The eventual FDA ban in January 2025 marked a significant shift toward consumer protection, prompting a move toward safer, natural alternatives for manufacturers. For consumers, this highlights the importance of reading ingredient labels for both food and pharmaceuticals to ensure a chemical-free diet. The controversy and eventual restriction of Red No. 3 underscore the ongoing reevaluation of artificial additives in the modern food industry. The FDA’s reversal on Red No. 3 emphasizes the evolution of food safety standards and the public's demand for cleaner ingredient lists, aligning the U.S. with many other nations that had previously banned or restricted the dye.

Frequently Asked Questions

The key ingredient in Red No. 3 is a synthetic compound called erythrosine, which is an organoiodine compound derived from petroleum.

Red No. 3 is manufactured by synthesizing fluorescein from resorcinol and phthalic anhydride, and then reacting the fluorescein with iodine through a process called iodination.

The FDA banned Red No. 3 because animal studies from the 1980s showed that high doses of the dye caused thyroid cancer in male rats, and the Delaney Clause mandates the prohibition of any food additive proven to cause cancer in animals or humans.

Natural alternatives to Red No. 3 include extracts from beet juice, purple sweet potatoes, red cabbage, and carmine, which is derived from cochineal insects.

No, Red No. 3 is not the same as Red No. 40. While both are synthetic, petroleum-based dyes, they have different chemical compositions and color properties. Red No. 3 has historically been linked to more significant cancer risks.

Red No. 3 was banned for use in cosmetics and externally applied drugs by the FDA in 1990, long before the ban was extended to food and ingested drugs.

Consumers can check the ingredient list on food and drug labels. The dye must be listed as "FD&C Red No. 3," "Red 3," or "E127".

No, Red No. 3 is not banned everywhere. Some countries, like Canada, still permit its use based on different interpretations of scientific data. The European Union has also restricted its use primarily to certain types of cherries.