It's True—Sienna Miller's French Skincare Secret Is Just £12 This Amazon Prime Day

Sienna Miller has long been admired for her laid-back beauty and perfect skin that looks effortlessly luminous. So—it's safe to say it raised more than a few eyebrows when the actor recently mentioned that she swears by A313, a thick, pharmacy-grade retinoid cream quietly beloved in beauty circles. It's a no-frills French formula, housed in an old-school metal tube, and while it doesn’t come with glossy packaging or a buzzy brand campaign, it’s earned cult status for a reason.

Unlike harsher prescription retinoids, A313 uses a blend of vitamin A derivatives that gently nudge the skin into glowier, smoother territory without causing chaos in the process. Miller described it as a tip passed along by a friend—Alexa Chung, no less—and noted how effective it is despite its humble price tag. It’s exactly the kind of product that’s easy to overlook until you hear someone like Miller casually name-drop it as part of her routine.

Right now, A313 is on Amazon for just under £13 this Amazon Prime Day, which is a fraction of what you’d pay for a glossy retinol serum with similar results. But part of the charm is that it doesn’t pretend to be fancy—it’s more of a beauty editor and off-duty model secret that’s been quietly passed around for years. The kind of product you don’t necessarily show off on your shelf, but never let yourself run out of.

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What Is Amazon Prime Day?

Amazon Prime Day is a sale event exclusively for Amazon Prime members and include some of the best deals you'll see on Amazon across the year with offers on top brands and products. Products range from the best of beauty to new-in fashion, with plenty of other savings on tech and homeware too. There are beauty tools we've been wanting to try, health and wellness items for a summer reboot, home appliances for chic spaces, and more great bits and pieces in between.

When Is Amazon Prime Day 2025?

Amazon Prime Day is a bi-annual event that runs in July and October each year. The next sale is on now, having started on Tuesday 8th July 2025 and is set to end on Friday 11th July 2025. This makes July 2025's Amazon Prime Day sale one of the longest-running in the brand's history.

How to Access the Amazon Prime Day Sale

Amazon Prime Day sales are available to all Amazon Prime members. You can sign up for an Amazon Prime membership here. It's free for 30 days so you can access all the benefits of the Amazon Prime Day discounts without shelling out a penny (just remember to cancel before the 30 days is up if you don't want to pay the monthly fee going forwards).