Ingredient

Cysteamine

A hydroquinone alternative for pigment. You leave it on about fifteen minutes, wash it off, and it smells strongly of sulfur.
Dr. Schwarz, MD · Board-certified dermatologistLast reviewed September 8, 2026
Four cysteamine products: a Senté tube, an Omic+ cream and box, a 5% cysteamine serum dropper and a Cyspera bottle

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I reach for cysteamine when someone needs real pigment treatment and hydroquinone is not the right answer, either because they have had a long course already or because no prescription is available. The evidence is reasonable, including trials run head to head against hydroquinone. The smell is the catch, and it is why people stop, far more often than irritation is.

The other thing I say at the start: it is slow, and it does nothing without daily sunscreen.

— Dr. Schwarz, Board Certified Dermatologist

Key Facts

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Also calledCysteamine hydrochloride, mercaptamine, Cyspera
TypeAminothiol; a pigment treatment for melasma and dark marks
Strengths sold5% cream is the studied and widely sold strength
UseOnce a day, short contact. Applied to dry skin, left about 15 minutes, then washed off.
Time to work8 weeks for early change, about 16 weeks to judge
Prescription neededNo in the United States, where it is sold as a cosmetic, often through dermatology offices

What It Is

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Cysteamine is a small sulfur-containing molecule your body already makes, from the breakdown of coenzyme A. It is in human cells and in human milk. As a medicine it has been used for years in tablet and eye-drop form for cystinosis, a rare inherited condition unrelated to skin pigment. Its use on skin is newer. Cysteamine is unstable and smells strong, and stabilizing it in a cream is what made it usable. That is the product you buy today, almost always at 5%. In the United States it is sold as a cosmetic, not a prescription medicine, and often through dermatology practices rather than a pharmacy. It is not FDA-approved for melasma. It has been studied in published trials, but it has not been through the approval process a prescription medicine goes through.

How It Works

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Cysteamine interferes with pigment production several ways at once. It blocks tyrosinase, the main enzyme pigment cells use to make melanin, and peroxidase alongside it. It binds copper, which tyrosinase needs to work. And it raises glutathione inside the cell, pushing melanin toward the lighter reddish-yellow form instead of dark brown.

Its real advantage is what it does not do. Hydroquinone can be toxic to pigment cells at higher strengths, and long uninterrupted use risks a stubborn discoloration called exogenous ochronosis. Cysteamine has not been reported to cause that and is not known to be toxic to pigment cells. That is why it can be used for longer stretches, and why it is often the maintenance step after a hydroquinone course.

Use it as a short-contact treatment — onto dry skin, about fifteen minutes, then washed off. Leaving it on longer does not work better and irritates more.

The evidence is moderate rather than strong. Several controlled trials exist, some comparing it directly with hydroquinone and finding the two broadly comparable, but the body of research is much smaller and the long-term data thinner.

Here is where Cysteamine acts in the skin.

About Cysteamine
Skin basics
SLOWS PIGMENT MAKINGCROSSES EASILY

Pigment is made inside melanocytes, cells spaced along the floor of the top layer of skin. Cysteamine slows the enzyme they use to make it, so less new pigment reaches the surface while what is already there sheds. As strong as hydroquinone in some studies, and it smells.

Cysteamine is small and crosses well. It is powerful for that reason, and its sulfur smell is the price.

The outermost layer, and the one every moisturizer is aiming at. It is dead — flattened cells stacked like bricks, with a mix of fats as the glue between them. That glue is what holds water in and keeps irritants out.

The outer layer, and the only one anything in a jar reaches. It renews itself constantly: a cell made at the bottom takes about a month to reach the surface and flake off. Most of what a skincare product does, it does here.

The living layer underneath, holding the blood vessels, the nerves and the collagen. It is where lasting change happens and it is hard to reach: most of what is sold for the skin never gets this far.

What It Treats

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Melasma

Melasma

Moderate evidence

Put on dry skin, left for about 15 minutes and then washed off rather than left on overnight. It is the over-the-counter option with the most real trial evidence in melasma, and it suits people who want to avoid hydroquinone or need something for the gaps between courses. The smell is the usual reason people give up on it.

Close-up of the lower cheek, nose and mouth of a young person with medium-brown skin, turned three-quarters away from the camera against a pale blue background. Scattered flat dark brown marks are spread across the cheek, with a few small raised spots still active among them.

Post-Inflammatory Hyperpigmentation

Moderate evidence

An over-the-counter option for stubborn brown marks, applied for a short contact time and then washed off, so it is a step rather than a leave-on product. It is the closest thing available without a prescription to a strong pigment treatment. The smell is unpleasant and some people find it stings, which is the usual reason people stop.

Not the Best For

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Sun Spots (Solar Lentigines)

Sun Spots (Solar Lentigines)

Limited evidence

Applied to dry skin, left for about fifteen minutes and washed off rather than left on overnight. It suits people who want a lightening step without hydroquinone, or something to hold a result between courses of it. Most of the trial evidence is in melasma rather than sun spots, and the smell is the usual reason people stop.

Forms

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Cysteamine is essentially one product — a stabilized 5% cream in a tube or pump, kept in the refrigerator to slow its breakdown. Most brands sell it as a kit with a cleanser or a soothing cream for after the wash-off, largely to deal with the smell. There is no prescription version and no gel, foam or serum. Storage matters, because the stabilization is what makes it tolerable at all.

A row of Cysteamine products sold as cream, 5%, photographed on white.
The only real form
Cream, 5%
A stabilized tube or pump. Applied to dry skin, left the stated time, then washed off.
Cream plus a cleanser
Kit
What most brands actually sell. The second product is there for the smell.
Not optional
Refrigerated storage
The stabilization is the product. A warm tube smells worse and works less well.
Uncommon
Compounded cysteamine
Made up by a pharmacy. Variable, and not what the studies used.
A row of Cysteamine products sold as second cream, photographed on white.
After the wash-off
Second cream
A soothing moisturizer for afterwards, usually supplied in the same box.

Strengths

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Not much of a ladder here. Almost all the published work and the products on sale use one strength.

WeakestStrongest
Below 5%5%Above 5%
Uncommon
Below 5%
Seen in compounded or newer products. Little published evidence.
The standard
5%
The strength used in the trials and in the products sold today. If a product does not state its strength, ask.
Not established
Above 5%
No better results, and the smell and stinging get worse.

Basics

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When to Apply
Once a day onto completely dry skin, not straight after washing — damp skin stings more. Leave it about fifteen minutes, wash off with a gentle cleanser, then moisturize. Most people use it at night because of the smell. Sunscreen every morning is part of the treatment.
How to Start
Every other day for a week or two, then daily. Some plans shorten the contact time instead, starting at five or ten minutes and building to fifteen. After a few months, most people drop to two or three times a week.
If It Irritates
Burning and redness during the contact time are common early and settle within two weeks. Shorten the contact time, apply to skin dry for half an hour, and moisturize afterwards. Persistent burning means cut back, not push through — irritation in pigment-prone skin makes new marks.
If It’s Not Working
Give it four months with daily sunscreen. If nothing has moved, the conversation turns to combining treatments, or to the trigger. Sun, heat and hormones drive melasma, and no cream outruns an untreated trigger.

Sample Routine

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Here is where Cysteamine sits in a day, and what goes around it. Pick what you are treating and what your skin is like, and the rest of the routine changes to suit.

What to Expect

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Weeks 1 to 2Weeks 4 to 8Weeks 12 to 16After 4 months
Adjusting
Weeks 1 to 2
Stinging, redness and the smell. Little visible change.
Working
Weeks 4 to 8
Patches start to lighten, gradually. Easier to see in photographs than in the mirror.
Judge it here
Weeks 12 to 16
Four months of daily use with sunscreen is a fair test.
Maintenance
After 4 months
Most people drop to two or three times a week rather than stopping.

What to Avoid

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  • Applying it to wet or freshly washed skin The most common mistake, and it stings much more.
  • Leaving it on longer than directed Longer contact does not work better and reliably irritates.
  • Sun without sunscreen Melasma is driven by ultraviolet light and heat. Daily sunscreen is part of this treatment.
  • Around the eyes and lips Or on broken skin. Short-contact creams sting badly there.
  • Layering strong acids or a retinoid In the same session. Use them at a different time of day.
  • The folklore the smell is often read as the product spoiling. It has not. Sulfur is what the molecule is, and no cysteamine is odorless.

If You Stop

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Melasma comes back if its triggers are unchanged, usually within a few months. That is true of every melasma treatment, and it is why cysteamine is usually continued at a lower frequency rather than stopped. Dark marks from acne or injury are less likely to return once cleared, as long as new spots are not forming. Nothing rebounds and nothing needs tapering. Stopping takes the brake off pigment production. The usual pattern is daily for a few months, then two or three times a week indefinitely.

Ask Your Doctor

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If you are pregnant or breastfeeding
Cysteamine on skin has not been studied in pregnancy. Ask the doctor managing your pregnancy first.
If burning or redness has not settled
After two to three weeks, it should ease with shorter contact times.
If a treated patch is getting darker
Rather than lighter. Worth reviewing.
If you have eczema or a rash there
It should settle first.
If you already use another pigment cream
Hydroquinone, a retinoid or acids. Stacking these needs a plan.
If the smell is stopping you from using it
There are other options. A treatment you cannot face is the wrong one.

How It Compares

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Hydroquinone

Hydroquinone

The same

The standard cysteamine is measured against. Head-to-head trials suggest broadly comparable results over a few months. Hydroquinone needs a prescription in the United States and is used in courses; cysteamine can be used for longer but smells strongly.

Five azelaic acid tubes and bottles on white, most marked 10 percent, from Peach Slices, Paula's Choice, Facetheory, The Ordinary and NaturiumLabeled cutaway diagram of a single skin pore, headed Azelaic Acid. The epidermis is a brick-textured band across the top and the dermis is pink below it, with a yellow oil gland at the base of the pore and a small cluster of bacteria inside it. Three callout lines point in: decreases dead cells in pore and kills bacteria are drawn in dark navy as main effects, and decreases inflammation is drawn in gray as a lesser one.

Azelaic acid

Worse

Gentler, cheaper, no smell, and it treats acne and rosacea at the same time. Slower and weaker on established melasma.

Five serums lined up on white, labeled tranexamic acid or niacinamide with TXA, including SkinCeuticals Discoloration Defense16:9 hero for Tranexamic Acid. Never cropped: the tone strip and the corner logo depend on the full frame.

Tranexamic acid

Different job

Stronger for the oral form than for the cream. Often combined with topicals. Oral use requires medical supervision because of clotting risk.

Topical retinoids

Worse

For pigment over the long term. Slower, and they irritate in a different way. Not used in pregnancy.

Chemical peels and lasers

Different job

Heavily dependent on who is doing them. Faster when they work, and capable of making melasma worse when they do not, especially in deeper skin tones.

Vitamin C and niacinamide

Different job

Limited to moderate evidence. Useful for maintenance and easy to tolerate, but not a match for cysteamine on active melasma.

Myths

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  • “The smell means it has gone bad.” The smell is the molecule. Cysteamine contains sulfur and smells like it. Warm storage makes it worse, but there is no odorless version.
  • “It is natural, so it is gentle.” Your body does make it, and it is not harsh the way a strong acid is. It still stings, and it is a real pigment treatment.
  • “It is a prescription drug.” In the United States it is sold as a cosmetic, often through a dermatology office rather than a pharmacy.
  • “It bleaches the skin.” It slows pigment production. Normal skin keeps its color, which returns after you stop.
  • “Leaving it on overnight will work faster.” It was studied as a short-contact treatment. Longer contact adds irritation without benefit, and irritation causes dark marks.

Questions Patients Ask

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How bad is the smell, really?

Bad enough to be the main reason people stop. It is a rotten-egg sulfur smell, strongest during the fifteen minutes the cream is on. Washing it off with the cleanser most brands include takes out most of it. Evening, in a bathroom with a fan, is what most people settle on.

Is it as good as hydroquinone?

Head-to-head trials have generally found similar results over a few months, but hydroquinone has a much larger evidence base, so similar in the studies we have is not the same as equally well established. Cysteamine can be used for longer stretches and needs no prescription in the United States. Hydroquinone is cheaper, easier to get in many countries, and does not smell.

Can I use it long term?

It appears so, and that is part of the appeal. It has not been linked to exogenous ochronosis, the discoloration that limits hydroquinone. Long-term data is still thin, so the usual approach is daily use for a few months, then a reduced maintenance schedule.

Does it work on deeper skin tones?

Yes, and melasma is more common in deeper skin tones, which is where most of the interest comes from. Manage irritation carefully, because inflammation in skin that pigments readily can leave new marks that outlast the ones being treated. And no cream works without daily sunscreen, including on skin that does not burn easily.

Why do I have to wash it off?

It was studied as a short-contact treatment. About fifteen minutes is enough for the cream to work, and washing it off limits the irritation and the smell.

Can I use it with hydroquinone?

Usually one after the other rather than together, with a hydroquinone course first and cysteamine to hold the result. Both at once mainly adds irritation. Make that plan with a dermatologist.

References

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