What is a Serum

In dermatology, if the most poorly understood and least specific diagnosis is eczema, then amongst skincare products, the most poorly understood term is “serum”. Just to make the point, which of the following do you think are serums? Vaseline pure petroleum jelly, Garnier Skin Renew Regenerating Serum, or Johnson and Johnson baby shampoo? In modern skincare, the connotation of the term serum has imparted to it an alluring aura of something high end, expensive, scientific and very effective. But today, you’ll get the real scoop on serums.

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There’s a huge disconnect between what a real serum is and the connotation of the term “serum” in modern cosmetic skincare. Technically, a serum is any product in which all the ingredients are in a single chemical phase, meaning that all the ingredients dissolve in each other without emulsifiers to hold them together, thereby forming a homogeneous mixture. So in fact, all of the products I just mentioned are serums. But there’s more to it.

Most skincare lotions and creams are either water in oil… or… oil in water emulsions in which the water and oil are held together by emulsifiers… so the water and oil don’t separate out as they do in salad dressing made of oil and vinegar. In serums, because all the ingredients dissolve in each other, THEY don’t separate out.

While technically, cosmetic serums can be either water or oil based, most are actually water based with or without some silicone. Because they boast a high concentration of their active ingredients, especially high tech actives, you only need to apply a few drops, so they tend to come in small bottles and are often more pricey than other skincare products. In line with their highly concentrated ingredients, they originally tended to be fairly specific in addressing single skincare concerns rather that being products that promise you that they treat multiple skincare conditions. So typically, individual serums were promoted for wrinkles, or moisturizing, skin lightening, and so on. But today, even this border has become blurred as some marketers try to promise more and more to increase sales.

Serums can be daytime or nighttime products. Like all other skincare actives, your face should be prepped with a cleanser and toner before application to insure optimal benefits. The order of application with your other skincare products obeys the same rules of lighter products being applied first, but because they tend to be lighter in texture to achieve a smooth and silky feel, and because they are concentrated so you only need to apply a few drops, they tend to be applied as one of the first products after cleansing.

Since the reality is that the concentrates in individual serums cannot be simultaneously used for all skin types or cure "all diseases", when buying a serum stick to products that address your specific problems, and as always, that are appropriate for your oil and water skin type.