It is just one of those things that so many do - even celebrities admit to doing it - but how bad can leaving your make-up on while working out really be? Let's sort fact from fiction.
First of all, why do some people decide to wear make-up in the gym?
One factor may simply be forgetfulness. After work, while looking for some quick exercise, it is easy to forget you applied foundation eight hours ago.
Also, some people are so used to wearing make-up they simply do not feel comfortable without it - any danger in that?
Well, according to Elle magazine, yes there is. In an interview with consultant dermatologist Dr Anjali Mahto, he stated that exercise, sweat, and make-up will seriously affect your skin.
Dr Mahto explained that when you are exercising and your temperature increases, the pores of your skin will open. If you are wearing make-up, it will begin to clog your pores and cause breakouts.
But it is not simply sweat that is an issue here. The dermatologist also emphasised that contact with bacteria through yoga mats, machines and hand-to-face contact are also leading causes of acne in the gym.
When it comes to foundation and concealer, it seems it is best to leave these products at home. But what is the verdict on eye make-up such as mascara and eyeliner?
The beauty community and skincare enthusiasts are still undecided on this one. Many claim that eye make-up will not affect acne-prone skin in the same way as foundation and concealer. However, others believe that wearing mascara will cause a build-up of bacteria and could cause eye problems in the future.
According to another dermatologist, Annie Chiu, in an interview with The Klog, although mascara will not clog pores, it can lead to dry, irritated, eyes as this area is so delicate.
It appears that we are better off leaving the beauty bag alone for an hour while we are at the gym and giving our skin a well needed break.