Antiviral reader Patrick wrote in to us because of the “constant claims” he sees on social media “that retinol (vitamin A) and related compounds help to keep skin youthful”.

To examine whether retinol really is the “road to ultimate youthful skin”, as one TikTok video claims, we turned to Dr Natalia Spierings, a consultant dermatologist and skin cancer surgeon in London with a reputation for her evidence-based, no-nonsense approach to skincare.

She conducted a systematic review – a type of study which involves analysing the quality of evidence and conclusions from the existing research to provide a comprehensive overview of the evidence – into the efficacy of over-the-counter vitamin A products.

What’s the difference between retinol and retinoids?

It’s important to distinguish between the terms used in product claims. Vitamin A is a nutrient essential for cell division, immune function and vision.

The term “retinoid” is the umbrella term used for all of the chemical compounds that are natural or synthetic derivatives of vitamin A, says Dr Deshan Sebaratnam, a dermatologist and conjoint associate professor at the University of New South Wales.

“This group of compounds regulates cellular proliferation [growth and division] and collagen production,” he says.

Retinol and retinaldehyde are specific over-the-counter retinoids, Sebaratnam says, while retinoic acid (tretinoin) and synthetic retinoids (like trifarotene and adapalene) require prescriptions from a doctor in Australia.

“These are much more potent than the precursors available over the counter,” he says.

So do any of these work to improve the condition of the skin to look more youthful?

What does the evidence say?

Spierings did a comprehensive search of research databases and found nine randomised, double-blind clinical trials that examined the efficacy of the compounds in over-the-counter products. Randomised, double-blind clinical trials are considered the gold standard in clinical research because of the controlled, systematic way of testing that limits the chance of bias and confounding factors influencing the results.

Four of the trials Spierings assessed reported no statistically significant differences between using a retinol-containing treatment and a base formula with no active ingredient in it. The remaining trials that claimed to provide evidence for retinol having a mild effect in reducing the visibility of fine lines and wrinkles were poorly conducted, she found, with methodological flaws that affected data collection and analysis.

Eight of the nine trials were sponsored by the manufacturers of the test products, raising concerns about bias and the objectivity of the results.

“There is no strong or trustworthy evidence published to date that the over-the-counter, non-prescription vitamin A derivatives that consumers purchase in skincare products has any ability to improve the appearance of aged skin,” Spierings says.

There have, however, been systematic reviews that found tretinoin or retinoic acid (the same thing, with different names) consistently improved the appearance of fine wrinkles, pigmentation and skin roughness, with statistically significant results across numerous studies.

There were limitations: higher tretinoin strengths showed stronger results, but was associated with a greater risk of skin irritation, and the authors also noted a lack of large-scale, standardised studies conducted longterm. More studies are needed to really understand which formulations and concentrations work best.

“Retinoic acid is the only cream that actually does improve the appearance of aged skin,” Spierings says. “Nothing else has been found to be as effective – not vitamin C, not acids, not niacinamide.”

Such products are generally only available on prescription because they “impart a physiological change to the functioning of the body … they need to be prescribed by a healthcare professional”, she says.

Is a prescription retinoic acid right for me?

Sebaratnam says all retinoids will cause some degree of irritation when they are first introduced. Dryness, flakiness, itchiness and redness are common, he says.

“Slowly incorporating a retinoid into your night-time skincare regime can help minimise this,” he says.

“Retinoids will smoothen out the stratum corneum (the top layer of the skin) and thus make your skin more sensitive to sunburn”, so sunscreen remains important, Sebaratnam says, and pregnant women should not be applying retinoids. Excessive vitamin A intake during pregnancy has been linked to fetal abnormalities.

The products also need to be used consistently and long-term. “It’s a bit like brushing your teeth to keep away cavities,” Sebaratnam says. “When you stop using the retinoids, the benefits don’t reverse, but you will no longer have the benefits they offer.”

Spierings says the most important thing to remember when it comes to healthy, youthful skin is that “there is very little you actually need to purchase from Big Skincare or Big Aesthetics to keep your skin looking healthy and youthful as you age”.

Instead, staying out of the sun and using an SPF 50 sunscreen, getting adequate sleep, managing stress, maintaining wellbeing and not smoking all go a long way towards maintaining healthy skin, she says. Genetics is a factor too.

And her key tip?

“Don’t buy random expensive skincare products.”

• Melissa Davey is Guardian Australia’s medical editor. She has completed a master of public health and moonlights as a fitness instructor

• Antiviral is a fortnightly column that interrogates the evidence behind the health headlines and factchecks popular wellness claims