Everyone has a bottle of this somewhere.

Trendy products come and go but there are some beauty buys that you're guaranteed to pick up time and time again. Whether it's a go-to foundation or miracle spot treatment, we all have one favourite that we can't do without. Bio-Oil is one of those old reliables - it's a household name and for good reason. Some people swear by it for smooth, supple skin while for others it's an essential for reducing blemishes and stretch marks. Online retailer Amazon has opened up about some of its users' favourite purchases and revealed that Bio-Oil is their best-selling skincare product of the past decade and the third top-selling product overall. It's got a few rather well-known fans too. Cheryl said that she puts the oil in the bath as part of her post-baby beauty routine to get a quick glow. The Kardashian sisters also use it. In a post on her website, Kim mentioned that she uses it an all-over body moisturiser while Khloe likes to wear it overnight. "I lay this stuff on really thick at night, go to bed, and let it work its magic," she said. You can pick up a bottle for as little as €9.99, but chances are there's some in your bathroom cabinet already.