One of the most important factors that makes the difference between good and great cosmetics products is pH. Even if you put the most expensive, exotic ingredients in your products, it won’t matter if your pH is not right. And while alkaline products have been the “trend” for some industry professionals, the truth is, we must consider all the factors when formulating a product.
You see, every region of our body has a different pH level which varies depending on the individual. That’s why one product can cause an allergy in one person and no reaction at all in another. And the tolerance is quite small. For example, the skin pH is between 4.5 to 5.5 on average. Someone with 5.5 skin pH might find a 4.5 product irritating. The pH of a final product must be carefully adjusted because not only can it cause irritation, it can bust your formula and spoil other ingredients completely. For example antioxidants must be kept in more acidic pH or they may be rendered ineffective. Also pH can affect the potential for growth of microorganisms in the product. And preservatives have their own pH tolerances, as do many raw materials.
These are just the basics of the basics on the subject of pH. The topic is so deep and complex, I could write an entire book about it and how it affects cosmetics products.