How to Evaluate a Skin Care Study

With more and more readers subscribing (thank you!), I am always happy to hear from such well-informed, well-read men and women.  Recently, many of you have been forwarding me studies and asking me if I could report on them in-depth on the blog.  And while I am happy to oblige, I think that Chinese proverb applies best here: “Give a man a fish, and you feed him for a day; teach a man to fish, and you feed him for a lifetime.”

Always remember:  Not all studies are created equal.  Not even all published studies.  For instance, a study finding that parabens in thousands of times the concentration found in the average skin care application induce cancer formation in mice cells in vitro (i.e., in culture) is a lot less profound that a study finding that, say, the paraben content in the average skin care application induces cancer formation in human cells in vivo (i.e., in the body).  (And breathe easy, my friends: the latter study is just a fictitious example, whew!)  

So what are some criteria you should look for to determine whether a skin care study is significant, irrelevant, or just plain advertising propaganda?   Here are some signs of a significant study:

• Large study size.  The larger the study, the more likely it is that the results are applicable to the population in general, not just the few people studied.
• Randomized.  People were not “selected” to be in the treatment group and “selected” to be in the control (no treatment) group; the process was randomized.  For more on randomized clinical trials, please click here.
• Placebo-controlled.  Basically, in simplified terms, if you give a patient anything, s/he tends to feel better.  This phenomenon has been well-documented.  In a placebo-controlled study, all of the patients (even in the control group) get something, so you can measure if the treatment is efficacious, not just the giving of a treatment.  For more, please click here.
• Published in a peer-reviewed scientific journal, as opposed to a company brochure or press release.  While there surely are great studies conducted outside the realm of published scientific research, well-versed scientists tend to give more weight to the studies in the journals, and so should you, as an educated consumer.  The peer review process simply keeps science honest by subjecting researchers’ work to a well-educated, not-to-be-duped board of equally brilliant researchers.  That’s why it’s hard to find “9 of 10 women report softer skin” in the headline of a science research journal article, as opposed to seeing it frequently in some product advertisements.  
• Not affiliated with the company of interest.  This can be extremely difficult, particularly in the U.S., where FDA approval is not required for the development and release of many skin care products.  As a result, sometimes the only research available about a skin care product or ingredients is conducted by its founding company.  In an ideal world, however, the studies are from independent third-parties investigating the efficacy of the product or ingredient.
• Human subjects in vivo (in the body).  It can be difficult to obtain these gems, but they provide valuable information.  Of course, if it is believed a treatment may cause cancer (or anything else!), it is only common sense to test in culture (in vitro) and not potentially harm anyone in the study.  Again, it’s just that the ideal case is human subjects in vivo; for instance, human subjects in vivo studies have shown the benefits of niacinamide, retinoids, and sunscreen (in identical twins) over time.  
• Concentrations are feasible to the subject of interest.  I have received a surprising number of e-mails and comments from angry consumers about the FDA choosing not to outlaw parabens from skin care products.  However, one of the reasons the FDA chose not to outlaw parabens in 2004 was simply because skin care provided very low levels of parabens in comparison to the levels used in the studies:  “Based on maximum daily exposure estimates, it was implausible that parabens could increase the risk associated with exposure to estrogenic chemicals.”  Of course, I’m not stating this to open up the parabens debate, as many well-informed, well-educated people have chosen not to use paraben-containing products.  I am just saying to be aware of the concentrations of chemicals used in studies.  (Even vitamins, like A and D, can be toxic in high levels!)  
• Repeated results, especially by other authors, in other studies.  When retinol (originally an acne treatment) was touted for its anti-aging properties in one study, it was a brilliant suggestion.  When retinol’s smoothing and wrinkle-fighting abilities were verified in several studies, it was a confirmed fact that retinol was an anti-ager.  And now that retinol is validated as an anti-aging powerhouse bythousands of studies, it is considered to be a gold standard by many dermatologists.  In other words, repeatability equals reliability.  To be a well-educated consumer, don’t be willing to throw out your skin care products (or buy all new ones, for that matter) on the basis of a single study.  Be patient, and keep reading.  Some great sources include The Journal of the American Academy of Dermatology, the journal Dermatologic Therapy, the textbook Cosmetic Dermatology-Second Edition (by Dr. Leslie Baumann, one of my favorite dermatologists!), and the following blogs: The Derm Blog (by dermatologist Dr. Jeffrey Benabio), The Skin Guru (by Dr. Baumann), Truth in Skincare, The Beauty Brains (by two cosmetic chemists), and, of course, your very own FutureDerm (I had to!).  🙂

Of course, I am still a medical student, so there are better, more thorough sources out there to teach you to properly evaluate studies.  One book I highly recommend is Rational Medical Decision Making, by the University of Pittsburgh School of Medicine’s own Dr. Goutham Rao.  I took his course on medical decision making last semester, and it truly changed the way that I evaluate studies.  Another favorite resource is How to Lie With Statistics, which provides funny look at how studies can manipulate you into believing what they want, although it is far less informative than Dr. Rao’s book.