My brunette hair always goes red in the sun – this £19 mask is the only thing that fixes it

My job, as a beauty editor, is completing a series of mini missions. It’s my responsibility to find the best facial sunscreens that sit nicely under makeup, and test the best hair straighteners so you don’t singe your hair to a crisp.

A mini mission I’ve been working on for around three summers now is finding a way to stop my brunette hair from going red in the sun. There’s always a lot of talk about how to care for blonde hair during the summer months. Cool-toned blondes are notoriously prone to UV-induced brassiness, or even a tinge of green when the ends dip into a swimming pool.

Walk into Boots, and there’s a line-up of purple shampoos, conditioners and masks for toning blonde hair ready to remedy the problem. But for brunette hair like mine that takes on a frustratingly warm, unwanted red tone in the sunshine? There’s barely anything that works.

I’ve tried blue shampoos and conditioners, but all they really do is stain my palms and make me look like I might have frostbite. There is one quite expensive green mask that takes the edge off, but only for a wash or so. But then, a clever, affordable buy came along that changed everything.

After a pre-summer colour appointment where I left the salon with a much warmer-toned brunette than I hoped for, I ordered Osmo Colour Revive Mushroom Colour Conditioner on a whim. I wanted a solution, and ideally a solution with next-day delivery.

I tried it almost as soon as the delivery driver handed over the package. The instructions recommend you apply evenly to towel-dried hair, or to dry hair for a more intense finish, for between three and ten minutes. I just did a small section of dry hair to begin with, in case it went terribly wrong, and left it on for four minutes.

Once the timer went off I rinsed it through and dried my hair to find that it was a much cooler brown. The shade is described as mushroom, and it definitely has that earthy tone to it. I was really chuffed, so I got straight in the shower to apply the mask all over. The end result was a bit darker than I might have predicted, and it pretty much covered up all of my lighter balayage pieces, but there wasn’t even a hint of redness in sight – mission complete.

I used the mask for the next two washes, and have kept it up every two weeks since to stop red tones from creeping in throughout the summer. If I use it too regularly, my hair can end up quite dark, but easing off for a few shampoos remedies that.

I like that it’s quick and easy to use, and saves me a lot of time, money and effort compared to visiting the hairdresser for a top-up toner in between my root touch-up appointments. On that front, it doesn’t cover greys, but it does make them slightly less noticeable.

If you’re also someone who finds their hair takes on a red tinge whenever the sun starts shining, or who can’t go without their hat on holiday for fear of undoing all the money they’ve spent at the hairdressers, this mask is truly a must-try.