Retinol and retinal — how they work, strengths and how to use them

Retinoids are the most-studied anti-ageing actives in skincare. They speed up cell turnover, boost collagen production, unclog pores and fade dark spots. But they're a family — retinol, retinal, retinyl esters and prescription tretinoin all behave differently. Choosing the right one, and using it well, matters more than choosing the strongest.

How retinoids actually work

All retinoids are converted, step by step, into retinoic acid — the form your skin cells actually respond to. Retinoic acid tells cells to renew faster, stimulates collagen and elastin, and normalises the way pores shed dead skin.

• Retinyl esters (retinyl palmitate) → retinol → retinal → retinoic acid.
• Each step of conversion takes work, so the further left on the chain, the slower and more skin-compatible it acts.
• Retinal is roughly 11× faster to convert than retinol, so it's noticeably stronger at low percentages.
• Tretinoin (prescription) is already retinoic acid — very effective, but often irritating.

Strengths, in real terms

• 0.01–0.03% retinal — beginner-friendly, K-beauty standard.
• 0.05–0.1% retinal — intermediate, visible firmness and tone results in 8–12 weeks.
• 0.25–0.5% retinol — beginner to intermediate.
• 1% retinol — advanced, only after your skin fully tolerates lower strengths.
• 0.025–0.1% tretinoin — prescription only; strong.

What retinoids can and can't do

• Can: fade fine lines, soften wrinkles, brighten, clear congestion, fade PIH, refine pore appearance.
• Can't: erase deep set wrinkles, replace SPF, work overnight, or undo severe sun damage in weeks.

How to introduce retinoids without wrecking your barrier

1. Start low — 0.03% retinal or 0.25% retinol.
2. Apply pea-sized amount to dry skin, 2 nights a week for the first 2 weeks.
3. Sandwich it: moisturiser → retinoid → moisturiser. This softens irritation with no loss of results.
4. Increase to 3–4 nights a week after 3–4 weeks if your skin is happy.
5. Never combine with AHA/BHA the same night. Never combine with high-strength Vitamin C the same routine.
6. Wear SPF 50 the next morning without fail. Retinoids make you more sun-sensitive.

Litsy's Korean retinal serums are formulated to be well-tolerated enough for K-beauty layering — browse the shop to find one that suits your tolerance level, or wait for our upcoming encapsulated retinal ampoule launching soon.