Canthaxanthin

This is the carotenoid worth a second look. In the 1980s it was the active ingredient in 'tanning pills' — and at those mega-doses it deposited (reversible) crystals in people's retinas, a condition called canthaxanthin retinopathy, with even a few aplastic-anaemia cases reported. That history is exactly why its safe limit, 0.03 mg/kg, is the strictest of any food colour — about 100x tighter than the synthetic dyes. The reassuring half: as an actual food colour in the EU it's barely used (one sausage), so EFSA found normal exposure stays under the limit. Dramatic backstory, low real-world food risk — but the low ADI is a legitimate flag.