The price of a brighter colour

Nearly every saturated colour in your wardrobe comes from the same chemical family. Azo dyes account for roughly 60 to 70% of all textile dyes, and they earned that dominance by being cheap, vivid and colourfast. Most of them are unremarkable. The complication is a subset that can break down into aromatic amines, compounds classified as carcinogenic, which is why the EU bans 22 specific azo dyes under its REACH regulation.

Twenty-two banned out of a family that colours most of the world's clothing. That's not a reason to fear your red dress. It is a reason to notice that the difference between a compliant dye and a banned one is invisible, unlabelled, and entirely dependent on choices made in a dyehouse you'll never see. Regulation covers garments sold in the EU; a lot of fast fashion is dyed for markets where nobody's checking.

Colour carries other passengers too. Heavy metals, including lead, chromium and cobalt, appear in some dyes and in fasteners, and dermatologists routinely trace adult contact dermatitis to disperse dyes along with formaldehyde resins and nickel snaps. If a garment has ever left a red, itchy outline where it sat against you, that's the mechanism worth asking about.

So here's a shopper's pattern worth filing away. Achieving an ultra-bright, deeply saturated colour at an ultra-low price means someone economised somewhere, and dye chemistry is one of the easier places to do it quietly. Neither brightness nor cheapness is proof of anything. Together, on a garment with no finished-product certification behind it, they're a signal.

The certification piece is checkable, by the way. OEKO-TEX Standard 100 tests finished garments, dyes included, against limits for more than 1,000 substances, and its Label Check lets anyone verify a certificate number free. A neon top that's passed that screen is just a neon top. One that hasn't is a guess you're wearing.