Glow Simplified
Check your shelf
Evening

Ingredient glossary

Cysteamine

What Cysteamine does for your skin, who it suits, and what to watch for.

INCI: Cysteamine · Also: Cysteamine Hydrochloride

Worth paying for

In short: Cysteamine delivers brightening and antioxidant, earns its place for pigmentation and melasma, and the evidence behind it is strong. One thing to know: not for pregnancy or breastfeeding; introduce it gently.

What it does
Brightening, antioxidant
Best for
Pigmentation, melasma
Watch out
Not for pregnancy or breastfeeding; introduce it gently
Evidence
Strong
How long
8–12 weeks
how it was measured

Measured on Melasma severity (MASI) and melanin index by mexameter; the first visit at which the change was measurable.

See it on the timeline, beside the others →

Does it clash with what you use? Check it →

Written by Maya Faour, founder and sole writer; not a dermatologistHow we work →

The molecule

Tap to turn it in 3D

The Glow take

One of the ingredients I trust most.

When your goal is fading dark spots and evening out tone, Cysteamine delivers, and the research properly backs it up. Skip it while you are pregnant or breastfeeding, and the rest of the time bring it in slowly.

— Maya

What it does

  • brightening
  • antioxidant

strong evidenceMultiple randomized trials and a systematic review show five percent cysteamine cream significantly reduces melanin indices and MASI scores and can match or…

Why we say this
  • Multiple randomized trials and a systematic review show five percent cysteamine cream significantly reduces melanin indices and MASI scores and can match or outperform hydroquinone-based formulas with mostly mild reversible side effects.

On a label: usually effective at 5%.

The thiol compound family, at a glance

2 thiol compound entries in the base, Cysteamine among them. 2 of the 2 are an active.

  1. Cysteamine77 Da
  2. Alpha Lipoic Acid206 Da
What the family shares: every one of the 2 is an active in the base.Ordered by molecular mass, lightest first, from PubChem's formulas.

How much do you need?

5%+

The vehicle-controlled trials worked from 5%; no published dose comparison sets a ceiling.

The trials, and what they used
  • Every trial uses 5%.
  • Cysteamine 5% cream, applied at bedtime for a short contact, beat placebo cream on mexameter contrast and MASI at 2 and 4 months in 50 patients with epidermal melasma (Mansouri 2015, double-blind, the maker co-authoring) and again in 40 patients read by Dermacatch and Mexameter (Farshi 2018).
  • Against 4% hydroquinone it lost on mMASI, 38% against 53% at 120 days in 40 women, with erythema and burning the common complaints (Lima 2020).
  • No dose comparison found; 5% is the only concentration ever tested and the only one sold, so the floor and the product are the same number.

Read the full reasoning →

Who it's for, and who should skip it

Tends to suit

  • pigmentation
  • melasma
  • postinflammatory hyperpigmentation

Approach with care

  • pregnancy
  • breastfeeding
  • very sensitive
  • compromised barrier
  • Clogs poresLow
  • Irritation riskModerate

How it fits each skin type

  • DryNeutral
  • CombinationNeutral
  • OilyNeutral
  • SensitiveTake care

Often chosen for pigmentation, melasma, postinflammatory hyperpigmentation. Take extra care if any of these apply to you: pregnancy, breastfeeding, compromised barrier.

Where it fits in your routine

WhenMorning or evening
Where in the orderAfter cleansing, before your moisturizer

Give it eight to twelve weeks — that is when the change first became measurable.

What was measured, and in whom
  • Measured on: Melasma severity (MASI) and melanin index by mexameter.
  • The vehicle-controlled randomised trial of 5% cysteamine cream in epidermal melasma, applied as a nightly short-contact regimen, ran four months with assessments at two and four months; MASI and melanin index were significantly better than placebo at the two-month visit, the earliest point measured, and improved further by four months.
  • 5% is also the marketed strength, so the number transfers to what people actually buy, though the population was Fitzpatrick III-IV epidermal melasma rather than mixed or dermal disease.
  • Later 16-week comparisons against 4% hydroquinone and triple-combination cream agree on the size of the effect.

Randomised double-blind placebo-controlled trial of cysteamine 5% cream in epidermal melasma reported by Mansouri and colleagues (Br J Dermatol, 2015); described rather than cited, PMID not verified.

Plays well with

Cysteamine, answered

Is Cysteamine safe during pregnancy?

No. Cysteamine is best avoided during pregnancy and breastfeeding. If you are pregnant or trying, leave this one out and ask your doctor about a safe alternative.

Who should avoid Cysteamine?

Approach Cysteamine with care if any of these apply to you: pregnancy, breastfeeding, very sensitive, and compromised barrier. Its irritation risk is moderate, so introduce it slowly and patch test first.

What concentration of Cysteamine actually works?

Cysteamine tends to be effective at around 5%. Much lower and it is likely underdosed.

During pregnancy

Leave Cysteamine out while you are pregnant or breastfeeding. It sits on the list of ingredients usually held back during this time.

When in doubt, check with your doctor or midwife. They outrank any website, including this one.When it is worth booking →

Compare Cysteamine with

30 comparisons built.

Can you mix Cysteamine with

2 pairings built.

This, for every label you own

One ingredient is easy. A full label is where it gets confusing. The Ingredient Decoder reads any product and tells you the honest truth, ingredient by ingredient.

Decode my products →

Sources & how we reviewed this

Last reviewed . Educational information about a cosmetic ingredient, not medical advice.

What changed on this page

  • : the highest dose tested
  • : what the EU regulates
  • : the effective dose from trials

See the full changelog →