SPF is essential? Absolutely.
We should be using a moisturizer at least 2x/day, every day? You bet.
...so for the sake of saving time, I can just mix these, right? Well...no.
While I see the logic behind this, and I was guilty of doing this myself years ago, it is simply.... not the move. Your moisturizer + SPF should be two staples in your skincare routine no matter what, but mixing them together detracts from the efficacy of both.
Let me explain why:
1. Mixing them makes your sunscreen easier to spread, but you're in turn reducing the amount of sunscreen that you are applying to your face & getting less coverage because of that. If spread is an issue, I recommend opting for a chemical sunscreen that rubs in a little easier than a strict mineral sunscreen.
2. Mixing the two alters the chemical makeup of the sunscreen, diluting it and decreasing the efficacy. Sunscreen formulation is NOT easy-- countless hours of research, trial & error, and strict approvals go behind each formula. Adding the chemical makeup of your lotion to that sunscreen throws it off balance and may impair the UV filters.
Suggestion: After cleansing + applying your serums, go in with your face lotion first. Allow that to dry & apply your sunscreen on top of that.
Tinted moisturizers & makeup with SPF can be good alternatives (only because they were specifically formulated to provide coverage + moisturize), but nothing beats using a true moisturizer + a true sunscreen on top of it. Add in a topical Vitamin C + Vitamin E in the mix and we are really talking full coverage!