Millie's on a real health and fitness drive right now, hitting the gym regularly, going to hot yoga sessions, eating super-healthy breakfasts and even posting Instagram snaps while out jogging in the rain.
So, it's no wonder the former Made in Chelsea star needs a miracle-working beauty product to help relax her tired muscles after such intense workouts!
And Millie revealed what her latest must-have is when she posted this snap (below) on Instagram after a 60-minute workout at Barrecore in London.
"This is so needed after my first @barrecore class #bathtime," Millie wrote.
Yes Millie's new bathtime best friend comes in the shape of Better You Original Magnesium Flakes, £9.95, betteryou.uk.com which, when popped in a warm bath, are the perfect way to help de-stress your body and relax aching muscles – especially after they've been worked to the absolute max.
They're also totally natural, vegan-friendly and a great way to boost your skin's hydration levels.
But will they give us a Millie Mack figure at the same time? Thought not...
No worries though, we're sold anyway!
If you fancy a warming, muscle-relaxing treat, you could also try Selexir Peace Bath Instant Serenity Bath Salts, £29, victoriahealth.com.
Or if you don't want to fork out quite so much hard-earned cash, try Deep Heat Muscle Rescue Bath Soak, £5.49, boots.com.
What's your post-exercise beauty essential? Let us know below. Our fave comment across the site each week wins £50!
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