What Are Retinoids?
Retinoids are a family of compounds derived from Vitamin A. They are the most extensively studied topical actives in dermatology, with strong randomised controlled trial evidence for acne treatment, photoageing reversal, collagen stimulation, and cellular turnover acceleration. All retinoids ultimately work by binding to nuclear Retinoic Acid Receptors (RARs), which then regulate gene transcription.
The Retinoid Conversion Ladder
Different retinoids have different potencies because they require different numbers of conversion steps before becoming the biologically active form — all-trans retinoic acid (tretinoin):
| Retinoid | Conversion Steps to Active | Potency | Availability |
|---|---|---|---|
| Retinyl Palmitate / Esters | 3 steps | Lowest | OTC |
| Retinol | 2 steps | Low-Moderate | OTC |
| Retinaldehyde | 1 step | Moderate-High | OTC/Specialist |
| Adapalene | Direct (selective RAR-β/γ) | Moderate (acne-specific) | OTC/Rx |
| Tretinoin | Direct (all RARs) | Highest | Prescription only |
What Retinoids Actually Do
- Stimulate fibroblast collagen synthesis via RAR-α activation
- Increase epidermal cellular turnover rate — speeding desquamation
- Reduce sebaceous gland activity (particularly adapalene)
- Normalise follicular keratinisation — preventing comedone formation
- Reduce MMP (matrix metalloproteinase) activity — preserving existing collagen
- Reduce melanin production by inhibiting tyrosinase
Concentration Guide
| Retinoid | Starting Dose | Effective Range | Notes |
|---|---|---|---|
| Retinol | 0.025–0.05% | 0.1–1% | Introduce 2x/week, increase over 12 weeks |
| Retinaldehyde | 0.025% | 0.05–0.1% | More effective per % than retinol |
| Adapalene | 0.1% | 0.1–0.3% | Photostable; can be used AM or PM |
| Tretinoin | 0.025% | 0.025–0.1% | Rx only; start low and go slow |
Retinisation: The 2–6 week adjustment period when skin first responds to retinoids with dryness, peeling, and sensitivity. This is a normal physiological response — not an allergic reaction. Support the barrier with ceramides and do not stop use. See the Glossary: Retinization for more.
Compatibility Rules
- Do not layer with high-concentration AHAs in the same application (pH conflict + over-exfoliation)
- Always follow with a barrier-supportive moisturiser
- Use SPF the following morning — retinoids thin the stratum corneum temporarily, increasing UV sensitivity
- Avoid during pregnancy — all retinoids are contraindicated (Category C/X)
For the anti-ageing science behind retinoids, see Collagen & Elastin. For acne use, visit Acne solutions.