Glycerin. Always the bridesmaid, never the bride – until now.

When I was little, my father told me that in Hollywood, actors’ tears were often not real – they were glycerin, smeared lightly under eyes then dropped on to an actor’s made-up face. The tears looked like water, but rather than drying out like water does, they stayed wet, ready to roll slowly down a slick actor’s cheek.

It strikes me that this sums up the function of glycerin in skincare, makeup and haircare rather well – it is there to add lasting moisture and retain water. In other words, it is both an emollient and a humectant, and easily one of my favourite ingredients in beauty, where it has been omnipresent for centuries.

And so it was surprising to see that on TikTok, glycerin (also know as glycerine and glycerol) has been trending as though it’s a scientific breakthrough and consequently, the industry is now focusing its marketing on this ingredient.

However, as with most things teenagers believe they discovered and claim as their own (Birkenstocks, Kate Bush, Peep Show), I’m all for it if it deservedly increases a product’s fan base and brings something worthwhile to a new generation. This is especially so when, as in the case of glycerin, it has been overlooked in favour of more fashionable hyaluronic acid and squalane (both of which I also love, just not quite as evangelically). The more love for it, the merrier.

Almost all glycerin used in beauty these days is derived from plants rather than animals (choose vegan products if you are still worried), it is tolerated by even the most sensitive skins and it’s cheap, which means it’s as likely to be sold by Sainsbury’s as by Sephora (pure glycerin is on sale in chemists, but it performs better in a team of moisturising ingredients than solo).

Glycerin is extremely helpful in maintaining a healthy skin barrier and suits all skin types, including oily and acne-prone ones, because it doesn’t clog pores. It is a dry skin’s best friend. Glycerin is also biodegradable, renewable and its production causes minimal waste.

I’ve no product recommendations this week, because to list glycerin-containing skincare would almost be like recommending my top five hotels with beds. It is possible to make products without it, but I can see few good reasons to do so. The joy of glycerin is that this is one beauty wonder ingredient you needn’t rush out to buy – it’s already sitting in your bathroom, quietly being brilliant.