Topical Retinol Explained Simply

1. What It Is About

Retinol is the alcohol form of vitamin A. Vitamin A is a fat-soluble vitamin, which means it dissolves in fat and not in water. Retinol is applied to the skin in ointments and creams. Importantly: Retinol does not act directly on the skin. The skin cell first converts it into an intermediate form and from that into another form that then acts in the cell. What is applied is therefore a precursor, not the substance that ultimately acts. It follows from this: How strongly retinol acts depends not only on how much is applied, but also on how well the cell can convert it. Studies measure very different things. Some look at cells in the laboratory, others at visible skin features such as wrinkle depth, others at tolerability. These levels are not interchangeable. A finding on cells in the laboratory describes a mechanism, not a skin outcome. In addition, retinol, retinyl esters and retinoic acid are chemically different and are absorbed differently.

2. What Studies Show

In humans the olfactory study is the key work. 170 patients with olfactory loss after an infection or after an accident took part 2. One part received only olfactory training, the others received olfactory training plus vitamin A administered into the nose. Olfactory performance was measured with a test that checks three things: how well someone perceives weak odours, how well they distinguish odours and how well they name them. After treatment, odour discrimination improved more strongly in the group with vitamin A than in the group with training alone 2. In patients after an infection, perception of weak odours also improved. Olfactory training ran for twelve weeks, vitamin A was given for eight weeks, and follow-up took place approximately ten months after the first measurement 2. The work provides an initial indication that vitamin A can support regeneration of olfactory cells. For the skin there is a review on nutrition and psoriasis from 2010 3. It evaluates controlled studies and classifies topical vitamin A derivatives in psoriasis as effective. It does not state participant numbers. A safety review examined possible harms when vitamin A is applied to and around the eye. It includes 10,794 participants 1. A retrospective analysis of 480 patients in South Africa and Germany examined collagen induction in fine wrinkles, sagging skin, scars and stretch marks 4. Vitamin A was only part of the preparation here, not the tested active substance. After one year a skin layer had become thicker, and patients in Germany rated their improvement as marked 4. An independent contribution of vitamin A cannot be derived from this. In human skin cells the most-cited work with vitamin A in the title describes that enzymes that break down collagen are inhibited and that collagen accumulates. This finding is preclinical, that is, from the laboratory and not in humans.

3. What Remains Unclear

For retinol on the skin a controlled study that tests retinol alone against a vehicle preparation is still outstanding. Controlled means the participants are allocated to two groups according to a fixed plan so that the comparison is fair. Such a study with clear skin features is still outstanding. The most-cited controlled work in the field examines topical vitamin C, not retinol. Further works concern vitamin E, K, B12 and vitamin D analogues. These substances have their own properties, their own preparations and their own indications. Results for them cannot be transferred to retinol. It is also open how much applied retinol the skin cell actually converts and how strongly this varies between individuals and skin sites. Equally open: Which skin features have been tested for retinol itself, and can a preparation be tolerated over a longer period?

4. What This Means in Everyday Life

Anyone searching for evidence for topical vitamin A often finds evidence for topical vitamins. The shared keyword is misleading: vitamin C, E, K, B12 and vitamin D analogues are different substances. Under the shared keyword the data situation for retinol appears more robust than it is when viewed separately. This is a hypothesis. In humans the application in olfactory loss has mainly been tested so far. For the skin the controlled examination is still outstanding. The mechanistic level is the densest part of the field: it is well described through which steps vitamin A reaches the skin cell. What is still outstanding is the clinical level. Next, a study would be needed that tests retinol as the sole active substance against a vehicle preparation, matches application duration and baseline skin condition, and captures both visible and histological features.

All details with study numbers and sources: detailed page on Topical Vitamin A (Retinol). For children: Topical Vitamin A (Retinol) for children.