Skincare and cosmetics are among the least regulated consumer products in existence. In the US, the FDA does not review or approve cosmetic ingredients before they go to market. In the UK and EU, regulation is better but still full of gaps — particularly around ingredients, which can be listed as a single word regardless of how many individual chemicals they contain.
Your skin is not an impermeable barrier. It absorbs a meaningful percentage of what you apply to it, particularly from products left on rather than rinsed off — moisturisers, serums, deodorants, period products. The chemicals below have enough evidence against them to warrant avoiding where possible.
This is not an exhaustive list, and science moves. But these are the ingredients with the strongest and most consistent evidence for concern.
Tier 1 — Avoid always
These have significant evidence of harm and no good reason to be in your products.
Parabens
What to look for: , , , , isobutylparaben
Preservatives used to extend shelf life. They mimic oestrogen and have been detected in breast tissue samples. The oestrogenic activity is real — the debate is about whether typical exposure levels are sufficient to cause harm. Given that they accumulate in the body and you're likely applying them daily across multiple products, the precautionary case for avoiding them is strong. Easily replaced with safer preservatives — there's no good reason modern formulations still use them.
Phthalates
What to look for: dibutyl phthalate (DBP), diethyl phthalate (DEP), dimethyl phthalate (DMP). Also hidden in "" or "."
Used to make fragrances last longer and to add flexibility to film-forming ingredients. Anti-androgenic — they interfere with testosterone and have been linked to altered reproductive development in studies on foetal exposure. Also found in nail polish and hairspray. Often unlisted because they're considered part of a formulation.
Formaldehyde and formaldehyde releasers
What to look for: DMDM hydantoin, imidazolidinyl urea, diazolidinyl urea, quaternium-15, bronopol (2-bromo-2-nitropropane-1,3-diol), sodium hydroxymethylglycinate
These compounds slowly release formaldehyde over time as a preservative mechanism. Formaldehyde is a known human carcinogen and a common cause of contact dermatitis. Found in shampoos, conditioners, nail hardeners, and some moisturisers. There is genuinely no good reason to use them when safer alternatives exist.
Hydroquinone
What to look for: hydroquinone (sometimes listed as 1,4-dihydroxybenzene)
A skin-lightening agent. Linked to a condition called ochronosis — permanent skin darkening with prolonged use — as well as potential carcinogenicity. Banned in cosmetics in the EU. Still available in OTC products in the US and UK. Often found in brightening serums and dark spot treatments.
Coal tar dyes
What to look for: ingredients beginning with "CI" followed by a number, or p-phenylenediamine in hair dyes
Coal tar-derived dyes are used in hair colours and some cosmetics. Several are classified as potential or probable carcinogens. Particularly relevant for hair dyes used frequently over years.
Tier 2 — Avoid where possible
These have meaningful evidence of concern but less clear-cut than Tier 1, or are of most concern at high or prolonged exposure levels.
Benzophenones (chemical sunscreens)
What to look for: (), avobenzone, octinoxate, octisalate, homosalate, octocrylene
Chemical UV filters absorb UV radiation and can be absorbed through the skin. in particular has been detected in blood, urine, and breast milk after topical application. It has oestrogenic activity in vitro. Mineral sunscreens (zinc oxide, titanium dioxide) are straightforward alternatives for most purposes.
Synthetic musks
What to look for: galaxolide (HHCB), tonalide (AHTN), musk ketone, musk xylene
Used as fixatives. They accumulate in the body and have been detected in human breast milk and blood. Some have shown hormonal activity. Found in perfumes, body lotions, and fabric care products. Another reason "" on an ingredient list is a red flag.
Triclosan and triclocarban
What to look for: , triclocarban
Antimicrobial agents once common in soaps and toothpastes. has been shown to disrupt thyroid hormone signalling and has contributed to antibiotic resistance. Banned from rinse-off soaps in some jurisdictions but still found in some toothpastes and other leave-on products.
PEGs (polyethylene glycols)
What to look for: any ingredient starting with PEG-, or polyethylene glycol
Used as emulsifiers and penetration enhancers. The concern with PEGs is two-fold: they can be contaminated with 1,4-dioxane (a probable carcinogen) during manufacturing, and as penetration enhancers they can increase absorption of other potentially harmful ingredients. The level of concern depends heavily on product formulation and the other ingredients present.
Silicones
What to look for: dimethicone, cyclomethicone, cyclopentasiloxane (D5), cyclohexasiloxane (D6)
Not a health concern in the same direct sense as the above, but cyclic silicones (D4, D5) are persistent environmental pollutants that bioaccumulate. D5 in particular is found in most conventional hair care products and has been detected in fish tissue. The case here is as much environmental as personal health.
On fragrance
"" or "" on an ingredient list is a legal catch-all that can conceal dozens or hundreds of individual chemicals — including phthalates, synthetic musks, and other compounds that would face more scrutiny if listed individually. This trade secret exemption exists in most jurisdictions and has never been seriously challenged.
The practical implication: if a product contains "" or "" and doesn't disclose what's in it, you cannot know what you're applying. For high-use, leave-on products like moisturisers and deodorants, this is a meaningful unknown.
-free means no compounds. Unscented sometimes means has been used to mask the natural smell of ingredients — it's not the same thing.
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Don't try to overhaul everything at once. Replacing one high-use product at a time when it runs out is a sustainable approach that doesn't require a significant upfront spend. Perfect is the enemy of meaningful progress.