Retinol, Retinoic Acid and Tretinoin: How They Actually Work in the Skin

Retinoids are one of the most researched categories of actives we have, with strong evidence for improving texture, pigmentation, congestion, fine lines and overall skin quality. But not all retinoids are the same, and understanding how they convert and how they work helps you use them properly.

Retinol, retinal and retinoic acid

Vitamin A comes in several forms, but your skin can only use one form directly, which is retinoic acid. Any over the counter retinol or retinal serum must first be converted inside the skin before it becomes active.

The pathway looks like this:

• Retinol converts to retinaldehyde
• Retinaldehyde converts to retinoic acid

Prescription tretinoin is already retinoic acid. This means it does not need to be converted. This is why it is more potent and faster acting, but also more likely to cause irritation if used incorrectly.

How retinoic acid works once it is active

Once retinoic acid reaches the receptors inside the skin, several important things happen.

• It increases cellular turnover.
• It improves how pigment is distributed.
• It supports collagen production by stimulating fibroblasts.
• It slows down enzymes that break down collagen.
• It balances oil production.
• It strengthens the overall structure of the skin over time.

These effects explain why retinoids are used for acne, sun damage, uneven tone, visible ageing and general skin renewal.

Why irritation happens

Most irritation comes from starting too fast or using too much. Retinoic acid speeds up skin turnover, and the skin can temporarily respond with redness, flaking, purging or sensitivity. This is not usually a sign of allergy or harm. It is simply an adjustment period.

How to use retinoids properly

The goal is consistency, not strength. A gentle introduction always works best.

• Start with one or two nights a week.
• Use a pea sized amount.
• Apply only to dry skin.
• Use moisturiser before or after if you are sensitive.
• Increase frequency slowly.

This approach reduces irritation and improves long term outcomes.

When prescription tretinoin is appropriate

For certain concerns, such as acne, deeper lines, stubborn pigmentation or moderate sun damage, prescription tretinoin may be appropriate following a medical assessment. It is not just a stronger version of retinol. It works differently because it is already in its biologically active form.

The take home message

Retinoids work. They work well when they are matched to the right skin, introduced gradually and supported with sunscreen and barrier friendly products. The best results do not come from the strongest product. They come from consistent use that the skin can tolerate.

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Written by Dr Brandon Kober-Brown MBBS, ProfDipMensHlth, GCCM

Registered Medical Practitioner (General Registration)MED0002581903

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‍Disclaimer:This article is intended for general educational purposes only and should not be taken as personal medical advice. It is not a substitute for a consultation with a registered medical practitioner. Prescription only medicines are classified as prescription only for a reason. They carry potential risks, require proper assessment and are not suitable for everyone. Always seek individual medical guidance before starting any treatment.