One of the so-called “beauty hacks” that’s floating around on the internet is that Milk of Magnesia supposedly makes a fabulous primer for oily skin. There are countless beauty gurus on youtube touting its mattifying tendencies. Bloggers who should really know better are recommending it. Makeup Alley has rated 4.1 out of 5 with 367 reviews.

Dear internet people: please don’t do this to yourselves. I sometimes wonder if internet browsing makes people’s skin better since they have easy access to research, or worse because they also have easy access to people’s crackpot theories about what they should put on their faces.

Y’all already know that there are a fair number of home remedies that make me cringe. Milk of Magnesia is the perfect example of this. Although there are some elements that may be helpful, it’s only helpful if you ignore the damage you may be inducing.

First of all, what the ever-loving fuck is Milk of Magnesia?

Milk of Magnesia is magnesium hydroxide suspended in water with a bit of sodium hypochlorite. Magnesium hydroxide is an inorganic compound patented in 1818 for digestive issues. It is formed by a simple salt metathesis reaction in which magnesium salt is added to ammonium hydroxide.

Mg2+ + 2OH —> Mg(OH)2

It is most commonly used as an antacid or as a laxative. When used as an antacid, the OH groups will pop on off the molecule and bind to the extra H+s you have in your painful, acidic belly, leaving you with water. This prevents your stomach’s hydrochloric acid from reaching your gastrointestinal nerves, meaning that you won’t be in horrible pain. Hooray! Science! When used as a laxative, you rely on Milk of Magnesia’s osmotic force. The magnesia ions formed after the OH groups pop off aren’t absorbed by your intestinal tract, leaving you with a high concentration of magnesium ions. Osmosis, at its most basic, is a movement of water from areas with low concentrations of ions to areas with high concentrations of ions. Thus, the magnesium pulls fluid into the intestines. Your colon sexily responds by dumping its contents, triggering you to dump yours. Hooray! Bowel movements!

The second key ingredient of Milk of Magnesia, sodium hypochlorite (NaClO), is standard household bleach, which is an oxidizing agent. It’s in a very low concentration (doctors don’t usually recommend drinking large quantities of bleach), but it is a very effective buffering agent.

Why the fuck do people want to put laxatives on their faces?

Against all odds, there actually is a pretty good reason why people put Milk of Magnesia on their faces. A study by Stewart and Downing (1981) showed that magnesium hydroxide is remarkably effective at breaking down wax esters and sterol esters extracted from human skin. These are the major components of the oil on your face.

In other words, it really actually is a de-greaser. It’s no surprise that people keep recommending this as an option for a primer. It definitely would minimize oiliness and I have no doubt that it has the potential to prolong your makeup wear.

Why is this a terrible, very bad, no-good idea?

Remember how magnesium hydroxide has a bunch of OH groups ready to jump out at you and neutralize any acid that may come it’s way? That means that Milk of Magnesia is alkaline as fuck. It has a pH of 10.5. For comparison, ammonia has a pH of 11. Baking soda looks downright harmless in comparison, with a pH of only 8.3.

In order to ward of particularly unpleasant bacteria, your skin needs to maintain a mildly acidic pH. P. acnes, for example, is best inhibited by a pH between 4.2 and 5.6. Your skin has evolved to maintain this balance very effectively. Your sebaceous glands secrete a thin layer of the acidic film called the acid mantle, which protects you from viruses, bacteria, and other potential threats. Milk of Magnesia was formulated to neutralize stomach acid. It’s going to do that, but on your face. This totally destroys your acid mantle, leaving your skin unprotected. Using Milk of Magnesia as a primer sounds like the perfect way to turn your face into a nasty-bacteria’s dream.

Interfering with the acid mantle may also cause contact dermatitis, interfere with the activation of enzymes involved in extracellular lipid processing, impede your skin’s ability to shed its dead layers, and damage overall skin integrity.

When you use Milk of Magnesia as an everyday primer, you are coating your whole face in this shit on a daily basis. This has the potential to be quite damaging. Milk of Magnesia may be effective for oil control, but there is a shitload of primers that can help control oil that is actually supposed to go on your skin. I would recommend buying one of those, instead.


1. The smell is nausea inducing to me. There is no way in hell I would coat my face in it.

2. I haven’t used it since I was a very young child, but I remember that it tasted AWFUL.

3. Well, this grossed me out. I’m really glad I never felt the need to try this one out.

4. Always do your research on home remedies!

5. I mean, technically using this logic, you shouldn’t be putting it in your stomach either, since the acid there also serves to prevent bacterial growth as well. I don’t think you should be using this on your face every day, just like I don’t think you should use it in your stomach every day. But I don’t see why using this every once in a while, as a quick, low-budget oil nuke would be a bad thing. A lot of makeup artists use this on brides because it’s the most effective, long-wearing oil-control method, and they have access to all kinds of products. If you have any recommendations for a product that is closer to the skin’s natural acidity but is still as effective, I would be interested.

6. I love your blog post – “what the ever loving fuck is the milk of magnesia?” made me laugh. I’ve never heard of using it as a primer before, yuck!

7. It’s unfortunately pretty common…

8. Somehow I missed the whole milk of magnesia as a primer craze… lesson learned?

9. Be glad you missed it!

10. It’s great for an emergency I suppose (I’ve heard of fellow MUAs using it on bald heads!) but I’m not sure where you’d go to pick it up that you couldn’t also pick up a primer or oil control powder!

11. It’s probably not a tragedy to use it one time, but it’s definitely not a smart choice!

12. Interesting! I’ve never even heard of this. Guess I don’t read enough beauty blogs.

When you get a chance, can you comment about the oil cleansing method (essentially washing your face with oil) and the no shampoo adding method (baking soda and vinegar for your hair)?

13. Do you have something in particular you want commented on? There are no clinical studies of either.

14. The other adorable blogger hack is the Monistat primer. ugh….I wish these hacks would die. For a group of people who love buying and trying new products, why suddenly go cheap with milk of magnesia?!

15. I mean, I bet most of the people using milk of magnesia and Monistat are on limited budgets and don’t have the resources to spend a ton on primer, but still love makeup and want to do full faces. But there are some steps you may just want to skip, especially if it is harmful…

16. Gossmakeupartist on youtube has mentioned it several times. I tweeted him a link to this post 🙂

17. My sister mentioned that her friend who has flawless skin used this. My poor little sister does in fact have oily skin but instead of listening to me and moisturizing more because she told me that her skin still feels tight after moisturizing she wanted to use this. I like how I’m the chemist but her friend in High School knows better than the graduate student. Ahem. End rant.

18. Hmmm maybe send her some resources? Kindly and lovingly?

19. I always wondered why folks were putting something so alkaline on their faces. A co-worker of mine swears by it but in her next breathe whines about her acne exaccerbations. Our MD’s keep out of this convo as they know how touchy-touchy some women can get when you question why they put crazy shit on their faces.

20. Oof, that’s a bummer. It’s easy to intervene when it’s someone you’re close to, but for some people (like coworkers)… you can’t say much unless they invite you to do so.

21. that’s a rude thing to say from someone who isn’t even a dermatologist! If I dont use Cetaphil on my face..I won’t rag on people who do!
this site is despicable

22. Sorry for the typo’s btw

23. This may not be the appropriate place to mention this, but I think I found the Beauty Bullsh*t to end all Beauty Bullsh*t. Have you heard about the lotion that supposedly turns all ambient light into a red-light facial?

24. HA! That’s hilarious.

25. I was just telling someone about this yesterday, but not nearly as eloquently or scientifically, so it’s great to have all of the specific data. Thank you!

26. Of course!

27. I personally love Milk of Magnesia. It’s freaking awesome. For digestive problems.

When I first heard about people smearing it on their faces it both seemed like a huge waste of good medicine and like “oh god no that somehow seems like a very fucking bad idea”.

28. People put lots of bad ideas on their faces…

29. MOM broke me out like a fucking bitch, so sad as it really mattified my oily face.

30. Is there a way to lower the PH of the solution?

31.  Someone, PLEASE tell me the name of a primer that actually works for very oily skin. I’ve tried dozens and dozens and the only thing that has been effective is MOM. And I actually have fewer breakouts… Maybe because there’s significantly less oil on my face?

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34. Wow, I wasn’t going to try it just wanted to know why almost everybody on Utube was recommending it. DF LOL….I WANT BE TRYING IT THANKS 4 THE INFO!!!! VERY HELPFUL.