Drew Barrymore swears by this serum for tighter skin and a youthful glow

We love a celebrity beauty product recommendation for the best mascara or best eye cream, learning the secrets behind their flawless looks. 

When you consider that the A-list have the pick of pretty much every brand out there, you know that they'll only use what they deem the best on their skin – and Drew Barrymore is no exception.

Luckily for us, the actress regularly posts her favourite skincare products on Instagram, including one particular serum that she claims helps to "youthen" her complexion. And considering how good her skin looks, you can bet we're taking notes!

The product in question is none other than the iconic Good Genes Lactic Acid Treatment from Sunday Riley. Posting a #BeautyJunkieWeek video to Instagram, Drew revealed that she had been using the cult product and was loving the results.

"I just do it once maybe two times a week," she said in the video last year. "It has this lemony, fresh sort of functional scent, but it's really great as it's doing this amazing polish to your face. Don't wear this out in the daytime; this is an indoor product. 

"If I just try this once or twice a week I see a huge difference in the brightening, the tightening and the youthening of my skin. 

"This tingles a little bit too, which always makes you feel like, 'Ooh, it's working!'," she added. "So trust on the Sunday Riley, it's cult for a reason!"

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In the UK formulation rules slightly differ, so the main ingredient is glycolic acid instead of lactic – but both formulas are equally well loved. 

Is this cult classic beauty product already a part of your skincare routine, or is it one to add to your wish list?