Cysteamine

Cysteamine is a brightening ingredient that helps visibly reduce the appearance of dark spots and stubborn areas of uneven tone.

• Before you start

  Skip it on the day of a facial, laser, microneedling or injectables, and for the week after.

• Best time

  Every study that specified a time used it at night.

• Where to apply

  Keep it away from the eye area.

• How to apply

  Apply to dry skin rather than freshly washed skin — if you have just cleansed, give it about an hour first. This is the single easiest thing to get right, and it makes it more comfortable.

• How long

  Follow the timing on the pack. Some cysteamine products are meant to be rinsed off after a short time rather than left on, and the two kinds are used quite differently. Leaving it on longer does not give a better result — the research points the other way.

• Sun

  Wear sunscreen daily. Cysteamine isn't one of the actives we flag for extra sun care - and sun exposure is what drives the look of the marks you're working on, so daily protection earns its place either way.

• Alongside others

  Moisturize straight afterwards. It is part of how this ingredient is meant to be used, not an optional extra.

• What to expect

  It has a distinctive sulfur-like scent. That is normal for this ingredient and not a sign anything is wrong.

• Expect some warmth, tingling or the look of mild redness in the first week, easing from there. Warmth on application tends to fade within about half an hour.

• Give it time — the change builds over weeks, and around the second month is when it tends to be at its best.

• If it doesn't suit

  Stop using it if the skin around a dark patch starts to look lighter than the rest, or if irritation persists.

Mild warmth, stinging or the look of redness may occur when you first start. Keep it away from the eye area. Not recommended during pregnancy or breastfeeding, as it has not been studied in either. Discontinue use if persistent irritation occurs, or if the skin around a dark patch starts to look lighter than the rest.

Six situations change whether Cysteamine suits your skin right now. Each one is either a reason to skip it, a reason to go slowly, or nothing to watch for.

Maternity & Nursing

Skip it

Fragile or Sensitive

Skip it

Recent Facial or Laser

Skip it

Prone to Redness

Skip it

Dry or Itchy Patches

Skip it

Recent Shave or Wax

Go slowly

Recent Shave or Wax — Avoid for 24 hours after waxing, threading, or dermaplaning.

Region	Most a cosmetic may contain
United States	No explicit cap
Canada	No explicit cap
European Union	No explicit cap
Great Britain	No explicit cap
India	No explicit cap
Brazil	No explicit cap
Japan	Not permitted in skincare (rinse-off hair products only)
South Korea	No explicit cap
Kenya	No explicit cap
Namibia	No explicit cap
Ukraine	No explicit cap
Georgia	No explicit cap
Australia	1% (unscheduled); 6% (with Caution labeling)
United Arab Emirates	No explicit cap
Kuwait	No explicit cap
Hong Kong	No explicit cap
Singapore	No explicit cap
Brunei	No explicit cap
Jordan	No explicit cap
Trinidad & Tobago	No explicit cap

Where a figure appears, that is the maximum strength allowed or advised for cysteamine in that market — some are set in cosmetics regulation, others are the ceiling a cosmetic safety panel recommends. Where no figure appears, the market either sets no cosmetic maximum or handles this ingredient outside its cosmetic rules. These are limits, not targets — the right strength for a formula is the formulator's decision. Some products containing this ingredient at higher strengths are prescription medicines, not cosmetics.

Open a market to see the rulebook its figure comes from. Those notes describe each market's own rules as we read them, current to August 24, 2026; the linked documents are the authority, and nothing here is legal advice.

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What is Cysteamine?

A brightening ingredient used on stubborn dark spots and age spots, to help the skin look more even in tone.

What else is Cysteamine called?

On a label you may see Cysteamine hydrochloride.

When should you apply Cysteamine?

Evening. Every study that specified a time used it at night.

How often can you use Cysteamine?

Daily, all over the face, not the eye area.

Where do you apply Cysteamine?

All over the face, not the eye area. Keep it off your lips too.

Can you use Cysteamine around the eyes?

No. Cysteamine goes all over the face, not the eye area.

Does Cysteamine make skin more sensitive to the sun?

No. Cysteamine is not flagged as increasing sun sensitivity.

What should you not use with Cysteamine?

Not on the same evening as Vitamin C. Space it apart from Exfoliants, Eye-area retinol and Retinoids.

Who should avoid Cysteamine?

Skip it if any of these apply: Maternity & Nursing, Fragile or Sensitive, Recent Facial or Laser, Prone to Redness and Dry or Itchy Patches. Go slowly with Recent Shave or Wax.

Is there a cosmetic limit for Cysteamine?

No. No cosmetic regulator in the United States, Canada, the European Union or Great Britain sets a maximum strength for it. That is a limit on the rules, not a signal to use more. Some products containing this ingredient at higher strengths are prescription medicines, not cosmetics.

Everything on this page traces to the sources listed below — regulators' own publications and published studies. Where the evidence does not answer a question, it is left unanswered.

Some sources below are the official product information for prescription medicines — some contain this ingredient at higher strengths, others are cited for how they interact with it. We use them for their safety and handling detail only. A cosmetic product is not one of those medicines and is not intended to treat any condition.

Our review is AI-assisted and is not a named expert's opinion. Last reviewed August 5, 2026.

Think something here is out of date or wrong? Email us at wiki@skinintelligence.ai with your reasoning and where you read it. We read what people send, and we update the page when the sources support it.