Sunset Yellow in Pregnancy: New Rat Study Finds Few Effects

A peer-reviewed animal toxicology study published online on October 2, 2026, in the Journal of Applied Toxicology found that prenatal exposure to the food dye Sunset Yellow (FD&C Yellow No. 6) did not cause maternal toxicity or adverse fetal developmental effects in pregnant rats across three tested doses. The researchers observed a narrower fontanelle at the highest dose tested, and the authors themselves call that observation preliminary and say it warrants further study, given the absence of other developmental toxicity and the normal variation in fontanelle closure. The study adds animal data on prenatal development; it was not designed to answer whether the dye is safe in human pregnancy.

Key takeaways

• A rat study published on October 2, 2026, evaluated the synthetic azo colorant Sunset Yellow (FD&C Yellow No. 6) across three oral doses during gestation.
• The abstract reports that Sunset Yellow did not adversely affect maternal weight gain, clinical signs, reproductive parameters, or fetal visceral organ development.
• A narrower skull fontanelle was observed only at the highest dose (640 mg/kg), which the study authors characterized as a preliminary finding that warrants further research.
• The study was conducted in Sprague-Dawley rats and did not test human pregnancy, childhood behavior, hyperactivity, allergenicity, or cancer endpoints.

What happened

On October 2, 2026, researchers published an experimental study titled "Evaluation of the Teratogenic Toxicity of Sunset Yellow in Sprague-Dawley Rats" in the Journal of Applied Toxicology. The paper is indexed under DOI 10.1002/jat.70463 and accessible via the PubMed record. The research was conducted by investigators at the Department of Preventive Medicine at Guangxi University of Chinese Medicine and the Institute of Toxicology at the Guangxi Center for Disease Control and Prevention in Nanning, China. The research was funded by the Guangxi Plateau Discipline: Nursing (Rehabilitation and Wellness) grant agency, with the full journal text currently behind a publisher paywall.

Sunset Yellow FCF is a synthetic azo colorant listed by the FDA as FD&C Yellow No. 6, and its European Union additive code is E110. The abstract describes it as a colorant widely used in food and pharmaceutical products and says that studies on its teratogenic toxicity in mammals remain limited. The study was designed to look for harm to the mother and to fetal growth and development after oral dosing during pregnancy in a standard laboratory rat strain.

To test this question, investigators randomly assigned fifty successfully mated female Sprague-Dawley rats to five groups. Three groups received Sunset Yellow at 40, 160 or 640 mg/kg. A negative control group received distilled water, and a positive control group received 300 mg/kg of aspirin. The substances were given by gavage (a tube into the stomach) for 10 consecutive days, from gestational day 6 through gestational day 15.

What changed

On gestational day 20, the pregnant rats were euthanized for necropsy, allowing researchers to evaluate reproductive parameters and perform physical inspections on collected fetuses. According to the published abstract, under the present experimental conditions, Sunset Yellow exposure at all three doses did not adversely affect maternal clinical signs, body weight gain, or reproductive parameters, nor did it cause any deleterious effects on fetal growth, development, or visceral organs.

The single notable variation emerged in the skull formation of fetuses exposed to the maximum experimental dose. The study abstract stated that although a narrower fontanelle was observed at 640 mg/kg compared with the negative control group, given the absence of other developmental toxicity and the normal variation in fontanelle closure, this finding should be considered preliminary and warrants further study. The fontanelle is the membranous gap between the cranial bones of a developing fetus.

Because the full paper remains paywalled, several detailed metrics were not disclosed in the abstract. These include the number of rats in each group, the total number of fetuses examined, the conflict-of-interest disclosures, and the full methods. The abstract also did not state whether doses were administered on a daily schedule or compare the rodent milligram-per-kilogram doses to average human dietary intakes. Most importantly, the study was not designed to evaluate behavioral development, neurodevelopment, hyperactivity, allergy sensitization, or long-term carcinogenic risk.

Who is affected

Because this was a laboratory rodent study, the findings apply to pregnant Sprague-Dawley rats dosed under controlled conditions. They do not show that the dye is safe, or unsafe, in human pregnancy, and the abstract does not compare the rat doses with what people eat. The authors also did not report any change in regulation or product recipes tied to this paper.

For shoppers, the practical link is the ingredient list: in the United States the dye is declared by name, usually as "Yellow 6". Our full ingredient review, Is Yellow 6 (Sunset Yellow, E110) Safe? Uses, Labels, Risks, covers where it appears and how it is regulated.

Fanta Orange is one example of a product that names the dye: its Open Food Facts listing includes "YELLOW 6, RED 40". Our side-by-side Fanta Orange vs Friendly's Orange Cream: Two Yellow 6 Labels compares two labels that both list it. This paper itself says nothing about Fanta or any other specific product.

What it means for shoppers

For shoppers reading grocery packages today, this publication does not change what is on the label. The study is about rats dosed during pregnancy; it makes no dietary recommendation for people, and the abstract does not compare its doses with human intake.

When reading ingredient lists, you can identify the colorant under these names:

• On United States food labels, look for "Yellow 6" or "FD&C Yellow No. 6" in the ingredient deck.
• On European Union packaged foods and imports, the color is declared as "Sunset Yellow FCF" or by its authorized number "E110".

If you want to know whether a product contains Yellow 6, the ingredient list is the place to check, because US rules require certified colors to be named. This rodent study did not find that Yellow 6 causes birth defects or maternal toxicity in the animal model it evaluated, and it did not test behaviour, hyperactivity, allergy or cancer.

The background

In the United States, the Food and Drug Administration's Color Additives in Foods page lists FD&C Yellow No. 6 (Sunset Yellow FCF) among the seven certified color additives approved for food. The FDA's color additive summary lists it under 21 CFR 74.706.

In Europe, the European Food Safety Authority announced on July 15, 2014, in Sunset Yellow: EFSA sets ADI, that it had established an Acceptable Daily Intake of 4 mg/kg body weight per day for Sunset Yellow, replacing the temporary ADI of 1 mg/kg body weight it had set in 2009. EFSA said estimates of consumer exposure were well below the new ADI for all age groups. The new rat paper does not compare its doses with that ADI, and the abstract does not state whether the doses were per day, so no direct comparison should be drawn.

What to watch next

The open question is the fontanelle finding. Because the authors call the narrower fontanelle at 640 mg/kg preliminary, and note the normal variation in fontanelle closure, further study would be needed to show whether it repeats or matters biologically. The full paper, including the numbers of fetuses examined per group, is behind a paywall.

Aurascan is a free food-label scanner app in beta on iOS TestFlight, with a waitlist for other platforms. Instead of a single numeric score, it explains each listed ingredient one by one with cited evidence. Scan a product that lists Yellow 6 and read what regulators say about each ingredient for yourself.