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Home » Red No. 3 food coloring — does it really increase risk of cancer?

Red No. 3 food coloring — does it really increase risk of cancer?

Red No. 3 is a food coloring used in some foods, many of which will be familiar to you. As the name implies, it’s a red dye that makes candies and foods look better. It’s really not been in the news for decades, but then someone sent me an article about it, which piqued my interest.

Predictably, the chemophobia crowd, like the Center for Science in the Public Interest, who thinks any chemical is a lousy chemical while ignoring the fact that every living thing on this planet is made up of billions of chemicals, is pushing the narrative that Red No. 3 causes cancer. You know what happens next, I go looking for any published evidence of whether the food coloring is linked to anything, including cancer.

Anyway, let’s take a look at Red No. 3 and find out what it does or does not do to humans.

bowl of candies
Photo by Ivan J. Long on

What is Red No. 3?

Red No. 3, also known as erythrosine, is an organoiodine compound, specifically a derivative of fluorone. It is a pink-colored dye that is primarily used for food coloring.

Interestingly, it has other uses beyond food. For example, it is used as a biological stain, a radiopaque medium for certain types of medical imaging, and a dye for identifying dental plaques. When your dentist wants to scare you with the amount of plaque on your teeth, they are using erythrosine.

When I was searching “erythrosine cancer” on PubMed, just to see if there was any research on Red No. 3 being linked to cancer, I found out that erythrosine is photosensitive, and when activated by certain wavelengths of light it destroys breast cancer cells. OK, this does not mean you should go buy a few kg of erythrosine in the hopes of stopping breast cancer, the research was in vitro (cells in a petri dish essentially) and the light has to be targeted to the cells.

My point is that the only thing I could find that linked Red No. 3 to cancer was that it is being investigated as a tool to treat cancer. That’s the definition of ironic.

Where did the link to cancer come from?

After my search for “erythrosine and cancer” on PubMed, I could find no clinical research, let alone systematic reviews (at the top of the hierarchy of clinical research), that showed a link between the consumption of Red No. 3 by humans and cancer.

That leaves us with animal studies only, particularly rats. A study published in 1986 in Mutagenesis concluded that rats, with a diet that was over 4% erythrosine. That is, 2464 mg/kg/day — if we translate that to a 100 kg human, that would be around 246 g of erythrosine per day. You’d have to eat 2000 bags of Skittles to consume that amount of Red No. 3, and I’m not sure that the food dye is going to be your most critical issue after consuming that much sugar.

But here’s the thing, maybe force-feeding rats that amount of Red No. 3 gave them cancer, but that has limited relevance to humans. There’s an old joke that we’ve caused cancer in rats hundreds of thousands of times, but very rarely has that knowledge been applicable to humans.

The FDA placed a partial ban on the dye as a result of this study. Although the dye can be used in foods, it cannot be used in cosmetics or externally applied drugs, because, at the time of the decision, it was thought it would have a carcinogenic effect if delivered in that manner. There really isn’t much evidence of that either.

Because of the fear, in the USA and Europe,  Allura Red AC (Red No. 40) is used more often as a red food coloring. And no, I’m not going to run down that rabbit hole to determine if Red No. 40 is dangerous.


I don’t know why Red No. 3 has suddenly become an issue for the Center for Science in the Public Interest, given that there is no clinical or epidemiological evidence of a link between the dye and cancer, but they seem to hate everything that isn’t “natural,” a logical fallacy.

I am certainly not going to consume 200 g of erythrosine every day for the rest of my life, but if my M&Ms have a few mg of it (and it doesn’t), I’m not going to worry about it. Plus, the food industry has moved on to other dyes, and I’m not worried about those either.

There are other things that should worry the reader with respect to cancer, and food dyes don’t make the list.


Michael Simpson

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