What Is Retinal (Retinaldehyde)? Difference from Retinol and Strength

Once the alcohol group of retinol is oxidised, retinal forms. So retinol passes through this step in the skin anyway. The logic of putting retinal directly in a product is to skip one conversion step. How much difference this makes in real life is less certain than marketing texts suggest.

Where does it stand between retinol and retinoic acid?

What makes retinal interesting is its position in the chain. Its step to retinol is two-way, meaning retinal can turn back into retinol. The step to retinoic acid is one-way. Moreover, this last conversion is thought to happen only in cells of suitable maturity, so the active form is considered to form more controllably.

What do the studies show about strength?

• Comparison with retinoic acid: In a study of about 125 people with sun damage on the face, 0,05% retinal, 0,05% retinoic acid and a carrier cream were compared. On skin-surface replicas taken from around the eyes, both active ingredients reduced wrinkles and roughness by week 18, while the carrier cream showed no significant change. The reduction was less pronounced by week 44. Retinal was better tolerated.
• Comparison with retinol: In a 23-person, 8-week half-face study, retinal cream (0,05% and 0,1%) produced more improvement than retinol at the same concentrations in most measurements. It is a small, single study.
• Comparison with carrier: In 40 people, 0,05% retinal increased upper skin thickness and elasticity. In an open-label study of 32 women, roughness and coarse wrinkles decreased over 4 months.

Advertisements may give figures such as "X times stronger than retinol". There is no large comparison in human skin that confirms this. One review also writes that retinal produces only mild improvement in wrinkles and skin texture. So retinal is a reasonable middle option, but if the concentration and formula change, the ranking can change too.

Tolerance: Does it really irritate less?

Compared with retinoic acid, yes. In a 14-day intensive patch test, retinal and retinol caused similarly low irritation, while retinoic acid caused markedly more irritation. Compared with retinol, the picture is less clear, because retinal caused more peeling in the same test.

Long-term data are also positive but limited. In a pilot evaluation of 229 people, 1% retinal was tolerated by up to 70% of users, and low concentrations allowed long-term use. In a group of 45 people who used it for 12-89 months, side effects were specifically assessed and tolerance was found to be good. Still, the retinoid reaction (itching, burning, redness, peeling) is also seen with retinal. Low irritation and no irritation are not the same thing.

Does it affect bacteria, and does it help acne?

A notable point where retinal differs from other retinoids is its aldehyde group. In the lab, among retinoids only retinal showed a clear antibacterial effect; it acted on gram-positive bacteria, including the one associated with acne. Bacterial counts decreased in the treated skin areas. This is an interesting finding, but it is not evidence for treating acne. Decisions in moderate or severe acne, and in cases linked to menstruation, rest with the dermatologist.

Retinal on labels and in regulation

It appears in the ingredient list as Retinal, and in publications as retinaldehyde. The EU's 2024 regulation sets upper limits for retinol, retinyl acetate and retinyl palmitate, but does not count retinal in the same line. This does not mean it is unlimited or risk-free; it only shows that the regulation targets those three substances. From a formula standpoint it is also a sensitive molecule. Like retinol, it is sensitive to light and heat, so opaque packaging that reduces air contact matters.

Who should not use retinal, and when should you see a doctor?

• Pregnancy, pregnancy planning and breastfeeding: Retinal is also a retinoid. It is not used; consult a doctor.
• Those new to retinoids: Starting with the lowest concentration is more cautious. Frequency and the logic of gradual introduction can be considered similar to those in the retinol usage article.
• Rosacea, eczema, very sensitive skin: Do not start on your own; ask your dermatologist.
• Those using prescription retinoids: Do not add retinal on top; talk to your doctor.

During the day, use a broad-spectrum sunscreen of at least SPF 30, renewed every 2 hours and after sweating or swimming. Keep in mind that most anti-ageing products need at least 6 weeks for an effect. If blisters, swelling or a widespread rash appears, stop and see your doctor. If dark marks remain after irritation on darker skin, see a dermatologist too.