Red flag
Evidence key Strong Moderate Weak How we grade
Banned in EU cosmetics Cancer classification Skin allergen Suspected genetic damage Chemical of concern
- What it can be used for
- Kills or slows microbes, makes alcohol undrinkable and preserves the product (the functions the EU ingredient database, CosIng, lists for it; a product may use it for any of them)
- CAS number
- 50-00-0
Why it’s flagged
Prohibited in cosmetics in the EU.
- Annex II entry 1577. Source: EU Cosmetics Regulation, Annex II (prohibited)
Annex II of the EU Cosmetics Regulation lists substances that must not be used in cosmetics sold in the EU.
Classified as a known or probable human carcinogen.
- EU classification Carc. 1B. Source: EU CLP Regulation, Annex VI harmonized classification
- IARC Group 1 (carcinogenic to humans). Source: IARC Monographs list of classifications
IARC Group 1 means carcinogenic to humans, Group 2A probably carcinogenic. EU Carc. 1A means known, 1B presumed to cause cancer in humans. These describe a hazard, not the risk at the amount in one product.
Classified as a skin sensitizer (may cause an allergic skin reaction).
- Skin Sens. 1A (H317). Source: EU CLP Regulation, Annex VI harmonized classification
EU hazard statement H317: may cause an allergic skin reaction.
Classified as suspected of causing genetic defects.
- EU classification Muta. 2. Source: EU CLP Regulation, Annex VI harmonized classification
EU Muta. 2: suspected of causing genetic defects.
Listed as a chemical of concern by the Campaign for Safe Cosmetics.
- “Formaldehyde and formaldehyde-releasing preservatives”. Source: Campaign for Safe Cosmetics
The Campaign for Safe Cosmetics is an advocacy group. Its profiles explain why it considers these ingredients a concern.
What the research says
- Formaldehyde in New Jersey homes averaged about seven times the outdoor level (55 vs 13 parts per billion). Strong evidence. Weisel 2002
- Scent chemicals released by perfumes and scented products can react with ozone in indoor air to form new pollutants, including formaldehyde and fine particles. Strong evidence. Alblooshi 2025
- Seal of Acceptance products must also exclude a named 34-ingredient Ecz-clusion List (including cinnamic alcohol, cinnamic aldehyde, coumarin, eugenol, farnesol, geraniol, hydroxycitronellal, isoeugenol, oak moss absolute and several citrus extracts), chemical UV absorbers other than titanium/zinc/iron physical sunscreens, and formaldehyde releasers, in any amount. Strong evidence. NEA 2026
- When scent chemicals from a pine-oil cleaner, an orange-oil degreaser and a plug-in air freshener met ozone in a lab chamber, about one formaldehyde molecule formed for every 3-5 ozone molecules they used up (yields of 20-30% in most tests). Strong evidence. Destaillats 2006
- Scent chemicals such as limonene and pine oil react with ozone indoors to make new pollutants, including formaldehyde and fine particles, that keep forming for hours after cleaning ends. Strong evidence. Nazaroff & Weschler 2004
- A dried film of pine-oil cleaner or orange-oil degreaser, with its scent chemicals already evaporated away, still produced formaldehyde and a burst of new particles when later exposed to ozone. Moderate evidence. Destaillats 2006
- In the same mouse study, formaldehyde formed by the limonene-ozone reaction, together with the leftover limonene itself, accounted for roughly three-quarters of the airway-irritating effect measured; formaldehyde was the dominant contributor. Moderate evidence. Wolkoff et al. 2008
- How much formaldehyde and particle pollution formed was set mainly by how much ozone was available, not by how much product was used, so running an ozone-generating air purifier or ionizer alongside scented cleaning products or air fresheners adds directly to indoor formaldehyde and particles. Moderate evidence. Destaillats 2006
About ingredients flagged like this one:
- The EU bans more than 1,400 substances from cosmetics, while US rules restrict only a handful. Moderate evidence. Alblooshi 2025
- In a survey of 187 US pediatric personal-care products, preservatives (57.8% of products) were a more common source of contact allergens than fragrance (29.4%), even though the products were being screened specifically for hypoallergenic/fragrance-related marketing claims. Moderate evidence. Hamann 2015
Each finding shows its evidence grade. See every graded fact or how we grade.
What this page can’t tell you
These lists describe what a substance can do, its hazard. The risk from one product depends on how much is in it and how you use it, and the label doesn’t say how much.
Not being on a list doesn’t make an ingredient safe. It may never have been assessed.
Check your products
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Official lists checked September 2026. Spotted a mistake? Tell us.