There’s nothing pretty about this. 

A watchdog group tested more than 20 top-selling at-home hair dyes and found toxic chemicals across the board — including a substance classified as a probable human carcinogen that showed up in every single one.

“Harmful chemicals have no place in our everyday products,” Oriene Shin, safety advocacy manager at Consumer Reports (CR), which conducted the deep-dive, said in a press release. “Not in the dyes adults use to cover their grays. Not in the chalk kids use for school spirit day. Not anywhere.”

Skin irritation is one of the most common complaints from hair dye users, with symptoms ranging from redness and itching to a burning sensation.

Beyond those short-term reactions, researchers warn the bigger concern is what repeated exposure over time could do to the body.

“Some compounds in permanent hair dyes are designed to penetrate deeply into the hair shaft, and once in the body, certain chemical ingredients or their breakdown products may contribute to DNA damage, inflammation or hormone disruption,” Dr. Adana Llanos, an associate professor of epidemiology at Columbia University, told CR’s Leigh-Ann Jackson.

For the investigation, CR sent 21 boxed hair dyes and two temporary hair chalk products sold online and in stores nationwide to a third-party lab for testing.

Researchers were looking for phthalates, heavy metals and volatile organic compounds, or VOCs — chemicals that easily evaporate into the air and can be inhaled.

Short-term exposure to certain VOCs can trigger headaches, nausea and irritation of the eyes, nose and throat. Over time, exposure has been linked to damage to the liver, kidneys and central nervous system. Some VOCs are also known or suspected to cause cancer.

“Our testing found that some hair dyes released VOCs at levels high enough to raise real concern, particularly for people who color their hair frequently at home,” said Ashita Kapoor, CR’s director for product safety.

One chemical stood out in particular: dichloromethane, also known as methylene chloride. Every single product tested contained it.

The compound is widely used in the US in products like paint strippers, adhesives and pharmaceuticals. It has caused cancer in animal studies and is classified as a probable human carcinogen.

Among the products tested, L’Oréal Paris Féria Downtown Brown had the highest levels of dichloromethane. Two versions of Revlon ColorSilk dark brown dyes ranked second and third.

While regulations generally restrict dichloromethane in cosmetics, CR notes there are narrow exceptions — including certain hair dye formulas — as long as products carry warning labels.

In a statement to The Post, a spokesperson for Revlon said the company “stands by the safety” of its products.

“Our quality standards are well established and remain strong, and we are confident in the products currently on the market,” they said.

L’Oréal Paris did not immediately respond to a request for comment.

The findings didn’t end with dichloromethane. The report also detected several other potentially concerning chemicals in many of the products.

Six, for example, contained toluene, a solvent linked to respiratory irritation and nervous system toxicity.

Four contained DEHP, a phthalate associated in research with everything from heart disease and insulin resistance to reproductive issues and early menopause.

One of the most alarming findings came from a hair chalk marketed, in part, for children at school events like “spirit day.” That product tested positive for benzene, a carcinogen linked to bone marrow cancers.

There was a small upside: 15 of the 23 products showed no detectable levels of the five heavy metals tested by CR.

Still, the rest weren’t in the clear.

Four products contained trace arsenic, a toxin linked to higher risks of cancer, cardiovascular disease and reproductive harm with long-term exposure.

Two contained lead, tied to neurological damage, immune and kidney problems and hypertension.

And six contained low levels of chromium, which can trigger severe allergic skin reactions, including intense itching, redness and blistering.

Industry groups pushed back on the findings, with the Personal Care Products Council telling CR that hair dyes are “extensively tested and deemed safe.”

“As with all cosmetics and personal care products, in order to market to consumers, companies must substantiate the safety of hair dyes and ensure their product labeling is accurate, truthful, and not misleading,” said Tesia Williams, a spokesperson for the group.

But experts not a key gap: not every ingredient has to be disclosed on the label. Fragrance blends, for example, can be hidden under proprietary formulas.

“Some chemicals are not always disclosed on product ingredients lists,” Llanos said. “And labels like ‘clean’ or ‘nontoxic’ or ‘plant-based’ aren’t tightly regulated, so these claims shouldn’t be taken at face value.”