Skincare Facts

Skincare Facts Backed by Research

Skincare advice changes fast, and much of it is repeated without a source. This page collects facts about skin and skincare products that are backed by published studies, dermatology organizations, or U.S. regulations, with each source listed at the end. Use them to cut through marketing claims and build a routine that does what it says.

Facts About How Skin Ages

1. Most visible facial aging is linked to the sun

In a 2013 study of 298 women aged 30 to 78, Flament and colleagues concluded that UV exposure seems to be responsible for about 80% of visible facial aging signs, including wrinkles, sagging, and uneven pigmentation. Age matters, but sun history matters more for how the face looks.

2. Daily sunscreen measurably slows visible aging

In a randomized trial of 903 adults under 55 in Australia, Hughes and colleagues found that people who used sunscreen every day showed no detectable increase in skin aging over 4.5 years, and had 24% less skin aging than people who used it only when they chose to.

3. Air pollution is associated with more dark spots

In a 2010 study of 400 women aged 70 to 80, Vierkötter and colleagues found that higher traffic-related particle exposure at home was associated with about 20% more pigment spots on the forehead and cheeks.

4. Short sleep shows on the face within a day

In a 2013 study, observers rated photos of people taken after 31 hours awake as having darker under-eye circles, more swollen eyes, paler skin, and more fine lines than photos of the same people after normal sleep.

For the full story on aging, see Why Do We Age?

Facts About How Skin Works

5. Healthy skin is naturally acidic

In a study of 330 people, Lambers and colleagues estimated the natural skin surface pH at about 4.7, below the value of 5 often quoted. The authors describe this slightly acidic surface, sometimes called the acid mantle, as beneficial for the skin's resident flora. Choosing a gentle cleanser is a simple way to respect it.

6. Drinking more water can raise skin hydration

In a 2015 study of 49 young women, adding about 2 liters of water a day for 30 days was linked to higher measured skin hydration, especially in women who normally drank less. It works alongside moisturizer, not instead of it.

7. Pure vitamin C needs a low pH to get into skin

A 2017 review by Pullar, Carr, and Vissers notes that vitamin C applied as ascorbic acid penetrates skin only when the formula pH is below 4. This is why vitamin C serums vary so much in results, and why formulators often use more stable vitamin C derivatives.

8. Antioxidants work better together

In a 2005 laboratory study on animal skin, adding ferulic acid to a solution of 15% vitamin C and 1% vitamin E roughly doubled its protection against simulated sunlight, from about 4-fold to about 8-fold. Learn more in What Are Free Radicals?

Facts About Labels and Product Claims

9. "Hypoallergenic" has no legal definition

The U.S. Food and Drug Administration (FDA) states that there are no federal standards or definitions that govern the use of the term "hypoallergenic." Each company decides what it means, so a patch test is still the best way to know how your skin will respond.

10. Ingredient lists run from most to least

U.S. cosmetic labeling rules (21 CFR 701.3) require ingredients to be listed in descending order of predominance. Ingredients at 1% or less may be listed in any order after the rest, and color additives come last. So the ingredients at the top of the list are present in the largest amounts. Our guide on how to read a skincare label walks through an example.

11. A cosmetic changes how skin looks, not how the body works

Under U.S. law, a product intended for medical use, or to affect the structure or function of the body, is regulated as a drug, even if it is sold like a cosmetic. That is why responsible cosmetic brands describe results in terms of appearance, such as "the look of fine lines," and why you should be wary of skincare that promises medical results.

Facts About Using Products

12. Sunscreen needs SPF 30 or higher and reapplication

The American Academy of Dermatology (AAD) recommends a broad-spectrum, water-resistant sunscreen with SPF 30 or higher, reapplied every two hours or after swimming or sweating.

13. More products is not better

The AAD notes that using too many products, especially several anti-aging products at once, can irritate skin. A short routine you use consistently is easier on skin and makes it simpler to see what works.

14. A real patch test takes more than one day

The AAD suggests applying a new product to a coin-sized spot on the inner forearm or the crook of the elbow twice a day for 7 to 10 days. At minimum, test on the inner arm for 24 hours before using a product on your face.

What This Means for Your Routine

  • Make broad-spectrum SPF 30 or higher your non-negotiable morning step, and reapply outdoors.
  • Choose a gentle cleanser that leaves skin comfortable rather than tight.
  • Pick one targeted serum for your main concern, and add new products one at a time after a patch test.
  • Read the top of the ingredient list to see what a product is mostly made of.
  • Look for appearance-based claims and published sources, and be cautious with promises of medical results.

For more myth-busting, read Skin Care Facts That You Should Know on the blog, and explore every topic in the Learning Library.

Frequently Asked Questions

What is the most important skincare fact to know?

Sun exposure has the biggest influence on how skin ages. A 2013 study concluded that UV seems to be responsible for about 80% of visible facial aging signs. Daily broad-spectrum SPF 30 or higher is the single most effective habit for the look of youthful skin.

What is the natural pH of skin?

Healthy skin surface pH is slightly acidic. A study of 330 people estimated the natural average at about 4.7. The study's authors describe this acidic surface as beneficial for the skin's resident flora, and a gentle cleanser helps keep skin comfortable.

Does hypoallergenic mean a product will not cause a reaction?

No. The FDA states that there is no federal standard or definition for "hypoallergenic," so the term means whatever each company decides. Always patch test a new product, especially if your skin is sensitive.

How do I read a skincare ingredient list?

In the U.S., ingredients are listed from the highest amount to the lowest. Ingredients present at 1% or less can appear in any order after the others, and color additives are listed last. The ingredients at the top of the list are present in the largest amounts.

How long should I patch test a new product?

Test on the inner arm for at least 24 hours before using a product on your face. For a fuller check, the American Academy of Dermatology suggests applying it to a small spot twice a day for 7 to 10 days. Stop if you notice redness or discomfort.

Sources

  • Flament F, Bazin R, Laquieze S, Rubert V, Simonpietri E, Piot B. Effect of the sun on visible clinical signs of aging in Caucasian skin. Clin Cosmet Investig Dermatol. 2013;6:221-232. doi:10.2147/CCID.S44686
  • Hughes MCB, Williams GM, Baker P, Green AC. Sunscreen and prevention of skin aging: a randomized trial. Ann Intern Med. 2013;158(11):781-790. doi:10.7326/0003-4819-158-11-201306040-00002
  • Vierkötter A, Schikowski T, Ranft U, et al. Airborne particle exposure and extrinsic skin aging. J Invest Dermatol. 2010;130(12):2719-2726. doi:10.1038/jid.2010.204
  • Sundelin T, Lekander M, Kecklund G, Van Someren EJW, Olsson A, Axelsson J. Cues of fatigue: effects of sleep deprivation on facial appearance. Sleep. 2013;36(9):1355-1360. doi:10.5665/sleep.2964
  • Lambers H, Piessens S, Bloem A, Pronk H, Finkel P. Natural skin surface pH is on average below 5, which is beneficial for its resident flora. Int J Cosmet Sci. 2006;28(5). doi:10.1111/j.1467-2494.2006.00344.x
  • Palma L, Marques LT, Bujan J, Rodrigues LM. Dietary water affects human skin hydration and biomechanics. Clin Cosmet Investig Dermatol. 2015;8:413-421. doi:10.2147/CCID.S86822
  • Pullar JM, Carr AC, Vissers MCM. The roles of vitamin C in skin health. Nutrients. 2017;9(8):866. doi:10.3390/nu9080866
  • Lin FH, Lin JY, Gupta RD, et al. Ferulic acid stabilizes a solution of vitamins C and E and doubles its photoprotection of skin. J Invest Dermatol. 2005;125(4):826-832. doi:10.1111/j.0022-202X.2005.23768.x
  • U.S. Food and Drug Administration. Hypoallergenic cosmetics. fda.gov
  • U.S. Food and Drug Administration. Is it a cosmetic, a drug, or both? (Or is it soap?) fda.gov
  • Code of Federal Regulations, 21 CFR 701.3, Designation of ingredients. ecfr.gov
  • American Academy of Dermatology. Skin care tips dermatologists use. aad.org
  • American Academy of Dermatology. How to test skin care products. aad.org

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

About the Author
Written by Kari Thomas, cosmetic formulator and founder of Skin Perfection.