The ultimate guide to which serum you should be using and when

Forget long lists of interminable ingredients and one-size-fits-all claims, we’ve recruited an expert to help decode the jargon when it comes to serums…

When it comes to skincare, a serum is the kind of thing most of us have in our collection to mindlessly apply at some stage of our routine.

But how many of us know what it actually is?

With more and more serums entering the beauty world, boasting different promises and super-ingredients touted to transform your complexion, it’s becoming increasingly important to be clued-up so that you can make the right decision for your skin.

We spoke to Dr Justine Hextall, Consultant Dermatologist at La Roche-Posay to help compile the ultimate guide to serums.

What exactly are serums?

Simply put, a serum gets the job done faster and more directly than other skincare products. 

They’re more potent than other formulas and contain higher concentrations of key active ingredients.

“Essentially, serums are liquid products that place concentrated ingredients which can penetrate deeper into the skin,” explains Dr Hextall. “It is the ideal vehicle to deliver actives into the skin.”

How are they different to moisturisers?

While a serum can target different concerns, one of which may be moisture levels, a moisturiser is purely for hydration purposes. 

It’s for that reason you should be using both a serum and a moisturiser as part of your daily skincare routine.

“Moisturising is about trapping and sealing in moisture to support the skin’s protective barrier and prevent water loss,” says Dr Hextall. 

“Ideally, a moisturiser is made up of humectants – such as glycerin and hyaluronic acid – to draw water into the top layer of skin, alongside products such as shea butter and ceramides, to seal in that moisture. 

“Our skin barrier has natural moisturising factors, and a good moisturiser will have ingredients very similar to those found in a healthy skin barrier.”

When should I be using them?

This all depends on the type of serum you’re using. 

Generally speaking, you should be applying a serum after cleansing and before you moisturise. 

The time of day, on the other hand, is down to the ingredients in your serum. 

If it’s retinol, you should be easing yourself into the serum a few days a week before applying it every night before bed.

You should also be following up with an effective SPF like La Roche-Posay Anthelios Ultra-Light Invisible Fluid SPF50+ as the ingredient leaves your skin more sensitive to UV rays. 

“I always recommend applying serums morning and night after cleansing and before moisturising to enable maximum absorption,” explains Dr Hextall. 

“If you’re applying more than one serum, apply the most fluid first. 

“For example, in the morning I recommend applying a vitamin C serum first after cleansing, then the hyaluronic acid and then a light moisturising lotion to trap that hydration. 

“In the evening, again after cleansing, I often recommend applying an active such as retinoid or an antioxidant serum, then hydrating products. 

“The benefit with serums is that they can be layered. That being said, just because a serum is available it doesn’t mean that it should be applied. 

“It is very important to balance actives with calming hydrating products. My mantra is active/repair – for a healthy skin barrier this approach is essential.”

For hydration

If you tend to experience tight-feeling, dry skin, you should seek out a serum that locks in hydration with targeted ingredients. 

The hero one to keep an eye out for? Hyularonic acid.

“From our mid-20s onwards we start to lose hyaluronic acid and the biggest drop is around the time of menopause,” explains Dr Hextall.

“Hyaluronic acid is a humectant that attracts water to the skin surface and occurs naturally in our skin. This hydrating and plumping of the skin cells contributes to that all-important skin bounce and glow.

“Applying hyaluronic acid to damp skin and boosting that hydration with a light moisturiser is perfect for those struggling with dry skin.”

“I love La Roche-Posay’s HyaluB5 as it has two different molecular weights. 

“The smaller molecules penetrate deeper into the skin and the larger molecules sit at the surface, allowing an even distribution of hydration.”

For blemish-prone skin

If your main issue is getting your skin to behave itself and to reduce the appearance of blemishes, you could benefit from a serum that contains the likes of AHAs (alpha hydroxy acids, which gently remove layers of dead skin).

Add a few drops to your nighttime routine before reaching for the moisturiser and you’ll give your skin a helping hand.

“The key with serums for blemish-prone skin is to unblock pores,” advises Dr Hextall. 

And the benefit of opting for a chemical exfoliant like a serum is that, unlike physical exfoliators such as harsh face scrubs, it won’t tear your skin.

“After application of an active serum, a light moisturising lotion should be applied to soothe and hydrate the skin,” adds Dr Hextall.

For radiance

A simple way of keeping your skin safe from everyday aggressors like pollution is to incorporate an antioxidant serum into your routine.

Just massage a couple of pipettes into your face and neck before heading out the door and let the active ingredients do the work.

“Vitamin C is one of the most powerful antioxidants, and as such it mitigates against free radical damage caused by exposure to pollution and UV amongst other factors,” says Dr Hextall. 

“The other major benefit of vitamin C are its skin-brightening properties. 

“It can therefore help to fade away unwanted pigmentation. So if you want smooth, firm, clear skin, remember to apply vitamin C.”

For future-proofing 

When it comes to the ultimate nighttime hero it’s all about one key ingredient: retinol.

“Retinols are derived from vitamin A,” explains Hextall.

“They work by binding with the retinoic acid receptors in the skin, which stimulates faster turnover of skin cells. 

“Retinols are probably the most evidence-based treatment to reduce the visible signs of ageing caused by UV exposure. 

“I always recommend that retinols are introduced slowly – I would advise a maximum of twice a week for the first week. I would then add an extra one to two nights per week until you can tolerate it once daily. 

“Apply a retinoid, followed by a light moisturiser half-an-hour after to hydrate and protect the sensitive skin barrier. 

“Sometimes the delicate skin around the eyes or the skin on the neck is less tolerant of a retinol. I recommend protecting this skin when this active is first introduced by applying a moisturiser to the area.

“This will dilute any retinoid that comes into contact with this easily irritated skin. 

“I often recommend the retinol by La Roche-Posay as it has been created to be tolerated by the most sensitive skin. It contains, alongside the active retinol, both vitamin B3 and glycerin to soothe and hydrate the skin.”

Choose the right serum for you with La Roche-Posay’s dermatologist-approved range of products.