The five types of ingredients in all skincare products

In previous posts, I’ve discussed skin anatomy, skin aging, and a few common skin conditions. This week’s post is about over-the-counter skincare products. What makes them work? What are the active ingredients you should look for?

Skincare products: Gels, creams, lotions… What’s the difference?

Is your skincare product a cream or an ointment?Wait… is that a cream or a lotion?

The first line of defense you are likely to use is some kind of cream. You’ve probably noticed that most companies make several versions of every skincare product – a lotion, a cream, an ointment, gel, or a serum. These words don’t have standard definitions, but the textures they connote are relatively consistent.

  1. Lotion: Thin liquid, usually a mix of oil and water. It’ll spread when it’s out of the container.
  2. Cream: Thicker than a lotion, about a 50-50 mixture of oil and water. It will hold its shape when it’s out of the container.
  3. Ointment: Very thick, possibly greasy, and occlusive (i.e. blocks the pores). This is about 80% oil and 20% water (e.g., Vaseline)
  4. Gel: Semi-solid like an ointment, but alcohol-based rather than oil-based.
  5. Serum: Usually contains a higher concentration of the key ingredient found in the cream or lotion version.

Active ingredients in skincare products

What makes any skincare product work is the active ingredient. Most of the ingredients in your favorite skincare don’t do much for the skin. They are preservatives, oils, fragrances – things that affect how the product feels and smells, but not what it does. The active ingredients are what act on your skin.

There are several types of active ingredients to look for in any given product: moisturizers, exfoliators, antioxidants, and cell regulators. Some of these ingredients have been shown in clinical trials to be effective anti-aging treatments.

About those skincare “clinical trials”

Be wary of study results you see in skincare advertisingBeware of advertising
Image courtesy XKCD

I should note that all clinical trials are not equally good. Just because a trial showed that a product had a “significant” effect on signs of aging, does not mean that it will work for you. Clinical trials frequently have problems. For example, they may have a very small number of patients, or a short duration of use. A lot of patients may have left the study without finishing it. Or there may not have been any randomization. Or worse, the results may be from tests done in a petri-dish. And, even if the trial was really well designed, the findings may be valid only for a very specific dose and skin-type. So the results may not apply to you or the product actually being sold! It takes some care to analyze a study, and skincare advertising usually leaves out most of the information you need to evaluate the results.

Every skincare product has a moisturizerMost skincare has moisturizers


Moisturizers make the top layer of skin (epidermis) softer, improve its barrier function, and prevent it from losing moisture. They can either form a thin layer that prevents water loss, or they can draw moisture to the skin. Well hydrated skin will have fewer fine wrinkles than dry skin. Effective moisturizers include glycerin, propylene glycol, sorbitol, urea, and hyaluronic acid. Most skincare products will have a few moisturizing ingredients in them.


Oxygen is necessary for life, but it is also the cause of a lot of our problems. A particular form of oxygen called Reactive Oxygen Species (ROS) is very harmful to cells. UV light and smoking both cause the formation of ROSs. But ROSs also occur with time and aging. ROSs tend to wreak havoc in their surroundings, damaging proteins and DNA. Antioxidants can neutralize these ROSs as soon as they form, making them useful for skincare but also in nutrition.

Antioxidants are probably the second-most common skincare ingredientAntioxidant-rich fruit

Vitamins C, B3, and E, lipoic acid , green tea extract , flavonoids, and reservatrol are all antioxidants. Most of these ingredients have multiple names. Look for these ingredients in your skincare to find the antioxidants.

  • Vitamin C – ascorbic acid, ascorbate
  • B3 – niacin, nicotinic acid, nicotinamide, niacinamide
  • Vitamin E – tocopherol
  • Lipoic acid – Alpha lipoic acid
  • Green tea – Camellia sinensis

Cell Regulators

What if we could get skin cells to behave as if they were still young? You may remember from the skin aging post that aging dermis produces less collagen and elastin. The right cell regulators might get an old dermis cell to start producing more collagen and elastin.

Some cell regulators commonly found in skincare products are: Palmitoyl pentapeptide, Argireline, Madecassoside (or Centella asiatica), and Salicyloyl-phytosphingosine.

Estrogen and progesterone have some cell-regulator effects too. They have been found to reduce the appearance of wrinkles. Estrogen can restore skin thickness, and enhances production of collagen, elastin, and hyaluronic acids. One study found that 2% progesterone improved skin elasticity in menopausal and post-menopausal women. Another study used 0.01% estradiol for 6 months and found similar results.

Skincare products that promise to rejuvenate the skin will often have chemical exfoliatorsSandpaper is an exfoliator…


Again, from the skin aging post you may recall that one sign of aging is irregular pigmentation of the epidermis. Exfoliation – removing the top, dead layers of epidermis – removes these irregularly pigmented cells and freshens your look. The two common types of exfoliators seen in over-the-counter skincare are alpha hydroxy (AHA) and beta hydroxy acids (BHA). The AHAs seen in skincare are: glycolic, lactic, citric, malic, and tartaric acid. There’s only one BHA – salicylic acid.

Interestingly, AHAs and BHAs also have some cell regulation properties. At the prescription-strength concentration, they have been shown to effectively instruct the skin to increase epidermal turnover and improve dermal thickness. There is, however, no conclusive evidence that the lower OTC concentrations do the same thing.

Carrots have a lot of retinoids, which have revolutionized skincareThat is a lot of Vitamin A


There are molecules that don’t fit neatly into the previous categories, and have multiple effects. The key ingredient here is Tretinoin (also called all-trans-retinoic acid, ATRA, and Retin-A), which is prescription only. It increases production of new cells in the epidermis and formation of new collagen in the dermis. It also improves the border between the dermis and epidermis. This reduces wrinkles and irregular pigmentation, and also decreases skin roughness. Related ingredients seen in skincare are Vitamin A, retinol, retinoic acid, and tazarotene which have similar effects, but are not quite as effective.

Tretinoin can cause birth defects, so it should not be used during pregnancy. If you are not pregnant (or likely to get pregnant), however, tretinoin is an absolutely fantastic option.

Always ask more questions, especially about skincareAlways ask questions


I hope this post helps you to interpret the ingredients in the over-the-counter skincare products you use. I encourage you to be skeptical if a product’s claims aren’t in line with its ingredient list. But ultimately, the process of finding skincare you love is going to include some trial and error. Everyone’s skin is different, so even if a study shows a product works for 75% of people, that doesn’t mean it’s definitely going to work for you. Similarly, even if it only works for 25% of people, it may be perfect for you. If you find something you love, hang onto it! But also remember that there may be something else out there with the same ingredients that’s cheaper.