Welcome to your skin check-in with Life & Style’s resident health and beauty expert, Dr. Will Kirby, a celebrity dermatologist and Chief Medical Officer of LaserAway. Every week, he’ll be spilling his candid thoughts and professional advice on all things skin, beauty and wellness as it relates to you — and your favorite stars.

There are so many amazing places to get beauty advice these days and while storied academic institutions contain volumes of advice and skincare experts have years of experience and unparalleled wisdom, the newest place to get cosmetic recommendations is from Bachelor in Paradise! During the Monday, August 16, episode contestant Kelsey Weier acknowledged that she uses Milk of Magnesia as a makeup prep and to stop facial sweating. But is this a legitimate beauty hack? I did some research to find out and the answer turns out to be not so simple!

To begin with, what exactly is Milk of Magnesia? Well, Milk of Magnesia (also known as “MOM”) is magnesium hydroxide, a compound typically taken by mouth intended to neutralize excess stomach acid or used to treat constipation. When applied on the skin, this compound absorbs oils and gives a matte finish which is great in a hot, humid environment like the tropical BIP setting! There are also anecdotal reports that it may minimize facial sweating. So, by minimizing oil and sweat and temporarily reducing shine, Kelsey basically created her own paradise primer!

But the good news immediately stops there. See, we absolutely want healthy bacteria to live on our skin and our facial skin, specifically, is ideally slightly acidic (typically 5.5 although it ranges from 4.0 to 6.0). In this acidic environment healthy, normal skin bacteria can populate your face. This is the reason why good skincare products are designed to be “pH balanced” and formulated with slightly acidic pH ranges (usually between 4.0 and just under 7.0).

Milk of Magnesia, however, has an alkaline pH and is usually in the range of about 10.5. So, short term topical, cosmetic use is probably no big deal but if you use it for too long and/or apply too much, you can alter your normal skin pH and disrupt the normal, healthy bacterial flora present. And when the pH of your skin changes it may allow new, harmful bacteria or fungal elements past the skin’s natural defenses. Also, changes in your skin’s natural pH also leads to increased water loss. Some common issues associated with milk magnesia use are redness, sensitivity, paradoxical excess oiliness, irritation, dryness and breakouts! Point being, the application of MOM has very real repercussions and consequences!

While I applaud Kelsey for trying her own DIY makeup concoction, I absolutely can’t endorse this concept. In my role as a dermatologist, I’d recommend that she — and you! — forgo the use of Milk of Magnesia as a facial makeup primer and a potential sweat/oil reducer and instead stick to tested products from reputable manufacturers that have been specifically formulated for facial use.