Should you apply skin care products in the order of what it is or by texture - water-based, then gel, then oil?
I would suggest using them in order of what they are intended to do, regardless of the weight. So, remove any make-up, clean skin, exfoliate (if you do this) treat specific problems and then apply a moisturiser to ‘seal in’ the products and complete the rehydration/restore lipid balance.
Begin with cleaning the skin and if you are exfoliating, do it after an initial cleanse. If this routine is at night, you may be removing makeup; waterproof or heavy makeup might need an oil cleanser, then use a hydrosol/other preferred cleanser, then exfoliate.
Next, apply products that are doing something specific, not necessarily to the whole face, so serums for hyperpigmentation, lightening products, Vitamin A or C serums, AHAs and BHAs etc. Typically finishing with a moisturiser to improve the hydration of depleted skin.
Whilst that sounds simple enough, there are some exceptions…you may have a product that does more than one thing. We make a very hydrating moisturiser, which contains vitamin A, kojic acid, hyaluronic acid and peptides, so this lightens dark patches of skin, smooth texture and strengthens skin too. But the active ingredients doing this are in a lower concentration than our serums, designed for specific problems.
In this case, having vitamin A in a serum and also in the moisturiser wouldn’t change the order you apply them to the skin. But it is worth just confirming exactly what is in each, why you are using them and how much is necessary for the desired result. There is a current trend for using very high percentages of active ingredients, like vitamins A and C, if you also have one of these in your moisturiser or elixir, this could be too much and possibly irritate skin.
The other point worth considering is that for some serums or elixirs to work evenly, it is better that the skin is already moisturised and any flaky skin removed, to allow the active ingredients to penetrate deeply enough to do what they are there to do. If you use a hydrosol to cleanse, this will also provide some moisturising, so you can apply a serum next. If you prefer to use a cleanser and toner, then adding a small amount of moisturiser before using the serum should allow it to work better.
PH is another area where the jury is still out… your skin’s pH will be about 5 (between 4.3 and 5.8). To work optimally, some products need to be in an alkaline solution and other an acid. (Neutral is 7, but your skin will always try to return it it’s happy place, which is actually slightly acid). There is no consensus about how long you should leave an acidic product to work before adding one more alkaline. I tend to think that your skin returns to where it wants to be fairly fast. But there are those who vehemently believe that you must use alkaline products at one time of day and acids another time and not mix them. If you are using two items with very different pHs - for instance, a vitamin C serum of pH 2.8 and a vitamin A with a pH of 6, you can simply add one to the morning routine and one to the evening. Although I just give the first one ten minutes to be fully absorbed before adding the second. I have tested skin, with a pH meter, after applying an acidic product to record how long the skin’s pH is changed, and each time, the skin was wending it’s way back to 5ish within ten minutes.
It is most important to know why you are using what you’re using. Then it should make sense to apply them in an order that will ensure each one is working optimally. Applying skincare should be pleasurable and relaxing, if it’s becoming stressful, rethink the process! If you don’t know why you are applying something, stop using it and see if you notice any difference, if not, save yourself the cost of buying it again.