Understanding the dermatological science of RETINDUO® Technology: Dual technology. Triple innovation.

Published on 25 March 2026
Roger Bloxham
Managing Director & Scientific Officer
Ferndale Pharmaceuticals Ltd.
Learn more about the author

RETINDUO® Technology builds on one of the most well-established pillars in dermatology. To fully appreciate its innovation, it is essential to first understand the science of retinoids and their role in supporting skin renewal and visible skin ageing.

Retinoids are vitamin A derivatives and are considered the gold-standard ingredient in dermatology for improving visible signs of skin ageing, including wrinkles, uneven pigmentation, rough texture, and loss of firmness.1-4

How retinoids work in the skin

Their effectiveness relies on their interaction with the skin at the cellular level. Retinol, retinal (retinaldehyde), and retinoic acid are retinoids naturally present in the skin, where they aid in renewing skin cells and, consequently, regenerating and regulating skin tissue and hydrators such as collagen and hyaluronic acid. Clinical studies using retinol and retinoic acid have demonstrated that they can:5-7

  • Accelerate epidermal renewal
  • Stimulate collagen synthesis
  • Improve skin texture and radiance
  • Reduce the appearance of fine lines

Products containing retinoic acid-related ingredients, such as tretinoin, are classified as prescription-only medicines in the United Kingdom, Europe, and the USA. Retinol, however, is a cosmetic dermatological ingredient that has been extensively studied and proven to produce skin changes similar to those caused by retinoic acid, helping it behave like younger, healthier skin without the need for a prescription.5-7

Retinol and retinal: Understanding these essential retinoids

Retinol is the retinoid predominantly found in the human body's circulation; it is delivered to skin cells bound to a special retinol-binding protein. In skin cells, retinoic acid is formed from retinol in a 2-step process, with retinal (retinaldehyde) as the intermediate. Retinoic acid is the retinoid that binds to special sites in the cell to stimulate skin renewal.5-7

Retinal is also a cosmetic dermatological ingredient that has demonstrated skin renewal activity by conversion to retinoic acid. Retinal can be converted back into retinol, and retinol can even form other retinoids that can be stored in skin cells to ensure there is a reservoir of retinoids that can convert to retinoic acid and stimulate skin renewal when needed.8-12

Within the skin, retinoids follow a metabolic pathway:

Retinol ⇄ Retinal → Retinoic Acid

By combining retinol and retinal, formulations can support the skin’s natural vitamin A metabolism through a complementary pathway. This combination with enhanced delivery mechanisms and bioavailability boosters is the scientific rationale behind RETINDUO® Dual Technology – Triple Innovation.

Introducing RETINDUO®: Dual Technology – Triple Innovation 

Building on decades of dermatological research, Cantabria Labs developed RETINDUO®, an advanced retinoid delivery system that combines complementary retinol and retinal with targeted formulation delivery and efficacy-boosting science.

  • Retinol encapsulated in microsponge: Microsponge technology enables controlled release and sustained activity of pure retinol within the skin.
  • Retinal encapsulated with AOX Technology: Unique AOX technology delivers retinal for rapid retinoid biological activity.
  • Natural Bioavailability Boosters: Advanced efficacy boosters optimise retinoid activity within the skin.

This triple innovation supports visible skin renewal while maintaining skin comfort and tolerability.

New ENDOCARE RENEWAL Retinoid Serums: Next-generation retinoid innovation

ENDOCARE is the science-led anti-ageing range within the Cantabria Labs dermatological skincare portfolio, delivering clinically proven targeted solutions to the skin barrier, skin radiance and skin renewal.

ENDOCARE RENEWAL Retinoid Serums are the latest innovation in the Renewal category with two progressive potency levels.

ENDOCARE RENEWAL Retinoid Serum

RETINDUO® potency level 1

  • Ideal for early signs of ageing
  • Suitable for sensitive skin
  • Perfect for retinoid beginners
ENDOCARE RENEWAL Retinoid Serum

ENDOCARE RENEWAL Retinoid Intensive Serum

RETINDUO® potency level 2

  • Ideal for more advanced signs of ageing
  • Suitable for skin already acclimatised to retinoids
  • Perfect for those stepping up from their use of ENDOCARE RENEWAL Serum

Key enhancing ingredients and features across both formulations:

  • Cross-linked hyaluronic acid for hydration
  • Niacinamide 4% to support the skin barrier
  • Airless packaging to protect retinoid stability and potency

RETINDUO® Technology and ENDOCARE RENEWAL Retinoid Serums: Clinical evidence

RETINDUO® (potency level 2) has been shown in ex vivo photoaged skin models to significantly boost collagen and elastin - key markers of younger, healthier-looking skin.

Clinical evaluation of ENDOCARE RENEWAL Retinoid Serum also demonstrated excellent user tolerability and visible improvements after 28 days of use:13

  • 90% reported softer skin and reduced fine lines
  • 85% reported improved skin texture
  • 0% reported redness or irritation

These results highlight the importance of combining effective retinoid activity with formulation technologies that support skin comfort.

Clinically proven results

To achieve optimal results in clinical use, participants using ENDOCARE RENEWAL Retinoid Intensive Serum followed a structured retinization protocol designed to enhance efficacy while minimising irritation.

This involved three progressive phases:14

  • Phase 1 Initiation (Weeks 1-2): Apply a pea-sized amount to cleansed, dry skin across the entire face twice weekly in the evening (e.g., Monday and Thursday).
  • Phase 2 Build-up (Weeks 3-4): Once Phase 1 is well tolerated (after Week 2 or later), increase application to every other night.
  • Phase 3 Optimisation (Weeks 5-8): Progress to nightly application, as tolerated.

A controlled clinical study evaluating ENDOCARE RENEWAL Retinoid Intensive Serum, used in conjunction with this progressive retinization protocol, demonstrated significant improvements across key skin parameters.15

Results demonstrated:

  • Increased skin hydration after 4 weeks
  • Improved skin firmness after 4 weeks
  • Increased skin elasticity after 8 weeks
  • Enhanced epidermal renewal after 12 weeks

Clinical images below show results after 12 weeks of using ENDOCARE RENEWAL Retinoid Intensive Serum:

Before and after 12 weeks using ENDOCARE RENEWAL Retinoid Intensive Serum using the dermatologist recommended retinization programme
Before and after 12 weeks using ENDOCARE RENEWAL Retinoid Intensive Serum using the dermatologist recommended retinization programme

Choosing the right ENDOCARE RENEWAL Retinoid Serum for you

ENDOCARE RENEWAL Retinoid Serum

  • Use if you are new to retinoids or have sensitive skin.
  • The first step in the ENDOCARE RENEWAL retinization process.

ENDOCARE RENEWAL Retinoid Intensive Serum

  • Use if your skin is already acclimatised to retinoids and you are looking for more intensified skin renewal.
  • The step up in the ENDOCARE RENEWAL retinization process.

Follow the Dermatologist retinization protocol for optimal results and skin comfort.

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FAQs

What do retinoids do for the skin?

Retinoids increase skin cell renewal and stimulate collagen and hyaluronic acid production, improving wrinkles, skin texture and uneven pigmentation.

How long does it take for retinoids to work?

Early improvements in skin texture and radiance may appear within 4 weeks, while improvements in firmness and elasticity usually become visible after 8–12 weeks of consistent use.

Can sensitive skin use retinoids?

Yes. Using a gradual retinization protocol and well-formulated products designed for tolerability can allow sensitive skin to benefit from retinoids.

Why should I wear sunscreen when using retinoids?

Retinoids increase epidermal turnover, which can temporarily increase sensitivity to UV and light. Daily use of broad-spectrum SPF50 sunscreen is recommended.

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References

1 Kligman LH, Grove GL, Hirose R, Leyden JJ. Topical tretinoin for photoaged skin. N Engl J Med. 1986;314(26):1636–1641.

2 Weiss JS, Ellis CN, Headington JT, Hamilton TA, Voorhees JJ. Topical tretinoin improves photoaged skin: a double-blind vehicle-controlled study. JAMA. 1988;259(4):527–532. ‌

3 ‌ Creidi P, Vienne MP, Ochonisky S, et al. Profilometric evaluation of photodamage after topical retinaldehyde and retinoic acid treatment. Dermatology. 1998;196(4):447–452.

4 Mukherjee S, Date A, Patravale V, Korting HC, Roeder A, Weindl G. Retinoids in the treatment of skin aging: an overview of clinical efficacy and safety. Clin Interv Aging. 2006;1(4):327–348. ‌

5 Kang S, Fisher GJ, Voorhees JJ. Photoaging and topical tretinoin: therapy, pathogenesis, and prevention. Arch Dermatol. 1997;133(10):1280–1284. ‌

6 Fisher GJ, Datta SC, Talwar HS, et al. Molecular basis of sun-induced premature skin ageing and retinoid antagonism. Nature. 1996;379(6563):335–339.‌

7 ‌ Kang S, Duell EA, Fisher GJ et al. Application of Retinol to Human Skin in vivo induces epidermal hyperplasia and cellular retinoid binding proteins characteristic of retinoic acid but without measurable retinoic acid levels or irritation. The Journal of Investigative Dermatology. Vol 105. No. 4. October 1995.

8 ‌ Napoli JL. Physiological insights into all-trans-retinoic acid biosynthesis. Biochim Biophys Acta. 2012;1821:152–167.

9 ‌ Fisher GJ, Kang S, Varani J, et al. Mechanisms of photoaging and retinoid therapy. Arch Dermatol. 2002;138:1462–1470.

10 Kafi R, Kwak HS, Schumacher WE, et al. Improvement of naturally aged skin with vitamin A (retinol). Arch Dermatol. 2007;143(5):606-612. ‌

11 ‌ Creidi P, Vienne MP, Ochonisky S, et al. Profilometric evaluation of topical retinaldehyde in photoaged skin. Dermatology. 1998;196:447-452.

12 ‌ Saurat JH, Didierjean, L et al. Topical retinaldehyde on human skin: biological effects and tolerance. The Journal of Investigative Dermatology. Vol 103, No. 6, December 1994.

13 Endocare Renewal Retinoid Serum Tolerance and Efficacy Assessment, 20 subjects with normal to combination skin (35-60 years of age), application to face once daily for 28 days. Subjective Evaluation. CRO: AlYeDerm Clinic & Research, Spain, (2025). Data on file. ‌

14 Kafi R, Kwak HS, Schumacher WE, Cho S, Hanft VN, Hamilton TA, et al. Improvement of naturally aged skin with vitamin A (retinol). Arch Dermatol. 2007;143(5):606–12. ‌

15 Prospective double-blind 40- female subjects (38-60 years) with skin types I-IV and moderate photoageing study, using a new Retinduo formulation or a clinically proven 0.5% retinol formulation randomized parallel arms. Subjects used the products following a progressive retinization protocol over 84 days.