The red dye once used on pistachio shells was a cosmetic food coloring, not a serious poison, but the specific dyes involved do carry real health concerns. The good news: red-dyed pistachios have been largely off the market since the 1980s. If you’re eating pistachios today, they almost certainly have their natural tan shell, and the dye question is moot. But if you’ve come across a nostalgic batch of red pistachios or you’re curious about the old ones you grew up eating, here’s what we know about the dye and your health.
Why Pistachios Were Dyed Red
For most of the 20th century, the pistachios sold in the United States were imported from the Middle East. Hand-harvesting left blotchy stains on the shells, and the drying process created mottled markings that looked unappealing on store shelves. Producers dyed the shells red to hide those imperfections and make the nuts look more uniform. One popular origin story traces the practice to a Syrian importer named Zaloom, who supposedly colored his pistachios to stand out from competitors. Detroit-based Germack, the first company to import pistachios to the U.S. in 1924, marketed them as “Red Lip pistachios.”
By the 1980s, California’s pistachio industry had taken off. American growers used mechanized harvesting that picked, hulled, and dried the nuts before shells had a chance to stain. The cosmetic problem disappeared, and so did the red dye. Today, red pistachios are a novelty item. A few specialty retailers sell them seasonally, but you won’t find them in a typical grocery store.
What Dyes Were Used
The red coloring applied to pistachio shells typically came from FDA-approved synthetic food dyes, primarily Red No. 3 (erythrosine) and Red No. 40 (Allura Red). Both are the same colorings found in candy, frosting, and other processed foods. The dye was applied to the outer shell rather than the edible nut inside, but anyone who ate red pistachios remembers the telltale evidence: bright red fingers, stained lips, and dye residue that clearly transferred during handling. Some of that coloring inevitably made its way into your mouth.
Health Concerns With Red No. 3
Red No. 3 is the more problematic of the two dyes. Studies found that it induced cancer in laboratory animals, which triggered a legal provision called the Delaney Clause. This clause, part of federal food safety law since 1960, flatly prohibits the FDA from authorizing any color additive shown to cause cancer in humans or animals. Despite this, Red No. 3 remained legal in food for decades due to regulatory inertia.
That finally changed in January 2025, when the FDA formally revoked authorization for Red No. 3 in food and ingested drugs. Food manufacturers have until January 2027 to reformulate their products. The dye had been primarily used in candy, cakes, cookies, frozen desserts, and frostings. Its removal from the food supply is a direct acknowledgment that the cancer risk in animal studies was sufficient to trigger a legal ban.
Health Concerns With Red No. 40
Red No. 40, the other dye commonly used on pistachios, remains legal but is not without controversy. A 2023 study published in Toxicology Reports found that Red No. 40 caused DNA damage both in lab cultures and in living mice. When mice consumed the dye alongside a high-fat diet over 10 months, they developed low-grade inflammation in the colon and significant disruptions to their gut bacteria. Populations of beneficial gut microbes dropped, while potentially harmful bacterial groups increased. The dye also activated a key protein involved in the body’s response to DNA damage, even at doses proportional to the amount considered acceptable for daily human consumption.
Red No. 40 is still permitted by the FDA, and the amounts present on pistachio shells were small. But the accumulating evidence has fueled growing skepticism about synthetic food dyes in general, and several countries regulate them more strictly than the U.S. does.
How Much Dye Actually Reached the Nut
The dye was applied to the shell, not the pistachio kernel. In theory, the shell acts as a barrier. In practice, the barrier was imperfect. Pistachio shells naturally split open before harvest, and the dye could seep through the crack to contact the nut inside. Even without direct contact, handling dozens of dyed shells and then touching nuts with red-stained fingers meant some ingestion was inevitable. The total amount was still small compared to eating a bag of red candy, but it wasn’t zero.
Are Today’s Pistachios Safe From Dye
If you’re buying pistachios from a major U.S. retailer, they are almost certainly undyed. The natural shells range from tan to light green, sometimes with slight mottling. That’s normal. The domestic pistachio industry eliminated the need for dyeing over 40 years ago, and consumer preference has shifted firmly toward natural, additive-free foods.
A handful of specialty vendors still sell red pistachios as a seasonal or nostalgic product. If you encounter them, check the ingredient label for the specific dye used. Any product still using Red No. 3 will need to be reformulated or pulled by 2027 under the new FDA order. Red No. 40 remains legal but is worth being aware of if you’re trying to minimize synthetic dye intake.
For the vast majority of pistachio buyers today, the red dye question is a piece of food history rather than a current concern. The pistachios on your shelf are the color nature made them.