This will be a short post on why MOM (Milk of Magnesia) isn't safe for long-term use on the face as an oil control primer.
I'm sure this "trick" has been around for awhile, but I know it became popular once YouTube "makeup artists" suggested this as an alternative for priming the skin, especially oily/acne prone skins.
The reality is that its a short-term fix, and I mean VERY short term. In the long run, you will risk serious skin problems like cystic acne due to increasing bacterial proliferation, and much more. Here is what MOM is used for and does in the body:
MOM is an OTC antacid and laxative! Not a facial treatment!
Magnesium Hydroxide (Mg(OH)2) is the active ingredient in MOM, accompanied by water and sodium hypochlorite (NaClO)
Mg(OH)2 is an antacid. Mg(OH)2 will dissociate in water and the basic hydroxide ions (OH-) combine with acidic hydrogen ions (H+) to turn into water and then neutralize.
In the use of a laxative, Mg(OH)2 relies on the magnesium ions (Mg2+) that form upon dissociation as described. These ions aren't absorbed in the intestinal tract, but it draws water from surrounding tissue to then increase water in the intestines. This makes fecal matter more passable.
Sodium Hypochlorite (NaClO) is a buffer/pH adjuster. This compound is commonly known as bleach. The amount of NaClO in MOM is extremely low but it is just enough to act as a buffer or pH adjuster. When this compound is dissolved in water, it will slowly break into sodium, chlorine and oxygen. This decomposition isn't something serious with the release of the chlorine gas, it is in such low amounts that it won't harm the body.
MOM can absorb lipids on the skin, as well as the small bleach content to help "degrease" surface lipids. Bleach is a very strong oxidizer which causes defatting of the lipids on the skin (meaning less oil).
Why you shouldn't use MOM on the skin:
MOM has the pH of 10.5, human skin has a pH of 4.7-5
Picture from FutureDerm.com
This will completely alter your skin and its balance. When this happens, you can develop contact dermatitis, increased acne, cystic acne, and much more.
Now you may ask, "If MOM takes away oil, why will it cause more acne?"
When you have an altered skin pH that is basic, that allows bacteria to grow. The acidity of our skin is a feature we have to lessen bacterial growth. It is a defense mechanism! Also, since the contents of MOM are "degreasers" you don't have the normal desquamation (shedding of cells) occurring on your skin. Bacteria + Dead Skin Cells = Acne!!!
Now, lets talk about some great oil control products!
Nuturing Force Blot Out Offensive: I use this in my professional kit and I swear by it. Keeps oil at bay for the entire day!
BECCA Ever-Matte Poreless Priming Perfector: This is a personal favorite of mine. It is a bit thick and takes a bit getting used to, but it will make your face a smooth, oil-free canvas for foundation.
Face To Face Super Matter Antishine: Absolute favorite amongst many artists in the TV/Film industry. It is not only great for controlling oil on the face, but also on men's palms, foreheads and balding areas. It comes in 3 sheer shades in light, medium and dark.