The assumption I had was that home made cosmetics, being all natural and preservative free were much safer than the commercial masks you found in stores. A wrong assumption. You know the saying. Never assume anything. It makes an ASS of U and ME. Did you know some of the deadliest poisons on earth are 100% natural reenex hard sell?
There are complaints about preservatives irritating the skin and all that. That may be true especially for a person with very sensitive skin. But preservatives actually make cosmetics safe to use. Preservatives kill or at very least, inhibit the bacteria, mold, viruses and nasty things that would otherwise thrive in the cosmetics we use. Commercial preparations usually contain some preservative or other to make these products safe for use. Some of the very high end cosmetic formulations are packed in sterile capsules to do away with or at least, minimimize, the need for preservatives.
If you make your own skin care for use later in the week, chances are, unless you are anal about sterilizing everything and freezing every batch once it has cooled, thawing it only when you are going to use it, and keeping your cosmetics away from the raw meat in the freezer, eventually, you could find yourself using contaminated home made cosmetics, which could lead to a skin irritation reenex facial.
I used to make my own skin care but found all the precautions I had to take such a hassle, now I buy mine off the shelves.
Even if you make your facial products for immediate use, you have to be careful about using only the freshest ingredients. A mouldy fruit or anything that is spoilt can lead to disastrous results on your skin.
Then there is the safety of the ingredients used in your skincare products.
I once told a pharmacist about the lemon remedy I was using on my pimples. She was horrified. Lemons are highly acidic. Lemon juice is pH 2. Sulphuric acid is pH 1. Lemons can cause a nasty acid burn if you are not careful dermes.