# A-04 — Hydroquinone

A depigmenting ingredient used in prescription pigment treatments. Diagnosis, concentration, companion ingredients and the clinician's course plan determine which evidence is relevant.

- **Canonical:** https://www.30plusskin.care/actives/hydroquinone
- **Site:** 30+/SKIN — Skincare, published as a spec sheet.
- **Issue:** ISSUE NO. 13 / REV. 2026.10
- **Standing terms:** INDEPENDENT · AFFILIATE-FUNDED · NOT MEDICAL ADVICE

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## Datasheet

- **INN / INCI:** Hydroquinone
- **Also known as:** Benzene-1,4-diol
- **Family:** Depigmenting agent
- **Molecular weight:** 110.11 g/mol
- **Layer reached:** EPIDERMIS
- **Prescription only:** yes
- **Evidence grade:** A
- **Controlled trials on file:** 2
- **Strength range recorded:** 4%–12%
- **Representative reference concentration:** 4%
- **Irritation (0–10):** 5
- **Onset:** 8 WK
- **Stability:** OXIDISES — REQUIRES AN ANTIOXIDANT SYSTEM AND OPAQUE PACKAGING

## Mechanism

The concentration marker is not a recommended dose or a claim that other strengths are untested. Compare the vehicle, indication and trial population.

Competitive tyrosinase inhibitor. Reduces melanin synthesis in melanocytes without reducing melanocyte number, which is why the effect reverses on stopping.

## Measured endpoints

| Endpoint | Effect vs comparator | Window | Record |
| --- | --- | --- | --- |
| Melasma cleared, trial 1 | +23% | 8 WK | REF-03 — Tri-Luma — trial 1, against hydroquinone + tretinoin in the same vehicle (Randomised, active-controlled against all three two-drug combinations in the identical vehicle, n=338, grade A) |
| Melasma cleared, trial 2 | +9% | 8 WK | REF-04 — Tri-Luma — trial 2, same protocol (Randomised, active-controlled against all three two-drug combinations in the identical vehicle, n=303, grade A) |

## Layering

- **Do not layer with:** Benzoyl peroxide, Indefinite use, Peroxides and resorcinol
- **Pairs with:** Tretinoin, A low-potency corticosteroid, short-term, SPF 30 daily

## Notes

- 4% is the concentration the evidence base is built on. This register has found it compounded at 6% and at 12% — the latter on body-sized surface areas, on open-ended monthly billing.
- Exogenous ochronosis is the risk that makes it a course. The approved label names it and notes that the majority of reported cases are in Black patients.
- The approved triple combination states in its own limitations of use that it is not for maintenance and that melasma usually recurs on stopping.
- In the trials, the two-drug arm without hydroquinone cleared nobody at all.

## A menu can describe several different prescriptions

Agency's current Dark Spot page includes hydroquinone and non-hydroquinone possibilities and describes clinician-directed transitions. It does not establish that every candidate ingredient is in one bottle, or that a single cycling calendar applies to all patients. Ask for the exact prescription and dates.

## Compare a compound with the appropriate record

The TRI-LUMA review provides a named finished-product reference with a specific melasma indication. That evidence should not be presented as a trial of every hydroquinone compound or every type of discoloration. AAD's melasma guidance places diagnosis and sun protection within the treatment discussion.

## Make the review point explicit

Ask how progress and irritation will be reviewed, whether a corticosteroid is included, and what treatment may follow the initial course. The shipment schedule should reflect the clinical plan. A recurring bill does not determine how long a particular ingredient should continue.

## Sources

- [Agency — Dark Spot Rx](https://agencyskin.com/products/dark-spot) — Current $110 price, 18 g / 60-day supply, possible hydroquinone and non-hydroquinone formulas, and clinician-directed transitions. Checked 13 September 2026.
- [American Academy of Dermatology — melasma treatment](https://www.aad.org/public/diseases/a-z/melasma-treatment) — Diagnosis, sun protection, hydroquinone, retinoid/corticosteroid combinations and alternative topical treatments. Checked 13 September 2026.
- [FDA — understanding compounded-drug risks](https://www.fda.gov/drugs/human-drug-compounding/understanding-risks-compounded-drugs) — Compounded preparations do not undergo FDA premarket review for safety, effectiveness or quality; they can meet individual medical needs. Checked 13 September 2026.
- [American Academy of Dermatology — pregnancy skin care](https://www.aad.org/public/everyday-care/skin-care-secrets/routine/pregnancy-skin-care) — Guidance to avoid retinoids and hydroquinone during pregnancy. Breastfeeding decisions need separate clinician advice. Checked 13 September 2026.

## Related records

- [R-16 Agency Dark Spot Rx](/reviews/agency-dark-spot-formula-review)
- [R-66 Strut Health Melasma Formula](/reviews/strut-melasma-formula-review)
- [L-11 Before a compounded melasma prescription: five questions to ask](/ledger/compounded-melasma-questions)
- [L-18 Prescription skincare follow-up: what to establish before the first refill](/ledger/prescription-skincare-follow-up)

## Products in the register containing it

| No. | Product | Stance | Score | Document |
| --- | --- | --- | --- | --- |
| R-35 | Galderma Tri-Luma | RECOMMENDED | 85/100 | /reviews/tri-luma-cream-review |
| R-26 | Obagi Nu-Derm Clear | CONDITIONAL | 74/100 | /reviews/obagi-nu-derm-clear-review |
| R-01 | Musely The Body Cream | CAUTION | 47/100 | /reviews/musely-the-body-cream-review |
| R-07 | Musely The Private Cream | AVOID | 36/100 | /reviews/musely-the-private-cream-review |
| R-43 | Nurx Prescription Skincare | CONDITIONAL | 74/100 | /reviews/nurx-prescription-skincare-review |
| R-45 | Skin + Me The Daily Doser | CONDITIONAL | 70/100 | /reviews/skin-and-me-daily-doser-review |
| R-16 | Agency Dark Spot Rx | CONDITIONAL | 75/100 | /reviews/agency-dark-spot-formula-review |
| R-66 | Strut Health Melasma Formula | CAUTION | 45/100 | /reviews/strut-melasma-formula-review |

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## Elsewhere in the register

- [Review register](/reviews)
- [Active monographs](/actives)
- [Brand register](/brands)
- [Evidence register](/evidence)
- [The ledger](/ledger)
- [How we test](/how-we-test)
- [Agent guide](/llms.txt)
- [Sitemap](/sitemap.xml)

_SOURCE-BASED ASSESSMENTS. PUBLISHER PREFERENCES ARE IDENTIFIED SEPARATELY._