I'd like to know if mixing different skincare creams/lotions/gels together into one composite cream will cause a chemical interaction that will inhibit any of the active ingredients. My purpose here is to have only one cream to apply in the morning instead of several, therefore saving time getting ready and space in my dopp kit. Active ingredients include tretinoin, clindamycin, azlaic acid, hydroquinone, and benzoyl peroxide.
On the same route, would mixing skin lotions containing glycolic acid, lactic acid, and anti-fungal and anti-inflammatory ingredients cause any reactions that would disable any of them?
You not only have to be concerned if the active ingredients will be inactivated, you also need to be concerned if there will be any reactions among the ingredients that could result in adverse effects. For instance, if some of the products are acidic and some are basic then there will be an acid-base reaction that can result in the generation of gases. In a closed container this can build up pressure and release explosively when you open the container. The cream that is formulated with benzoyl peroxide uses ingredients that are compatible with the peroxide which, chemically speaking, is an oxidizing agent (a bleach). These are notoriously reactive with many other chemicals - mixing it with other formulations would not be prudent.
Without seeing ALL the ingredients in these formulations you want to mix no one can give you a definite answer. And considering the number of permutations of reactions that could take place this is just too complex to predict.
You have to consider that, if it was really possible to mix all these different ingredients to get all their different effects in one product, a professional formulator would have done it. There are probably fundamental chemical incompatibilities that do not make that possible.
In general it is a bad idea to mix commercial formulations, especially when they contain acids, bases, oxidizers, biocides, etc. It is a better strategy to examine whether you really need all these different products or if some of them are redundant. For instance, glycolic acid and lactic acid fulfill the same purpose in a formulation - they are both alpha hydroxy acids that exfoliate the skin. If you are using two products one after the other where one contains glycolic acid and the other lactic acid you're exfoliating twice - you should consider whether you need that level of wear and tear on your skin.
A very good answer by Karen. As she says, you'd want to find out the pH compatibility of each, and the interactivity of each with various compounds. You may find this from the supplier's of each, especially the 'active' compounds, as he points out. It's just outside my area of experience, so I would recommend searching out a topical skin care formulator/scientist who makes this class of products on a regular basis. They would know the ins and outs off the top of their head. you may be able to search that particular 'consultant' (one who can work on many company's products, rather than just the one they work for) at www.scconline.org, there's a resource button that leads to consultants, contract mfrs/private label mfr, and supplier's. what state are you in....firstname.lastname@example.org