409 AI-Guided Skin Care
patterns from multiple elements, the STS algorithms synthesize numerous precisely
defined data points, generating a science-based, custom skin care regimen and personalized
educational content. This tailored approach culminates in quantifiable improvements in
skin health and reproducible positive outcomes.
IMPORTANCE OF CORRECT SKIN TYPE DIAGNOSIS
At the core of efficacious personalized skin care is accurate skin type diagnosis. In the realms
of machine learning and AI, the adage “garbage in, garbage out” holds true. Feeding an AI
system inaccurate skin type data will result in suboptimal product recommendations, lead
to incorrect advice, and possibly adversely affect skin health.2 With a live dermatologist
consult to diagnose skin type, other options to identify skin type include questionnaires,
imaging, and bioinstrumentation.
SKIN CARE QUIZ
The BSTI3,4 was developed and validated at the University of Miami between 2004 and
2010 using skin bioengineering devices such as the sebometer, tewameter, and mexameter.
This science-based skin type questionnaire is the only valid skin type test5 and is a
recognized diagnostic tool used in research studies to diagnose skin type (Figure 1).
Described in multiple medical textbooks6–11 and used by dermatologists12–14 and skin
care researchers worldwide,15–20 it is the gold standard in skin type diagnosis. The BSTI’s
accuracy is backed by various studies, confirming its reliability across different genders,
ethnicities, and geographic locations.21 This consistency is vital for researchers, cosmetic
chemists, aestheticians, medical providers, and dermatologists who rely on the BSTI for a
precise skin type diagnosis. Use of the BSTI quiz found at SkinTypeSolutions.com ensures
that the skin type data input into AI systems are accurate, enhancing the quality of
personalized skin care recommendations and educational content.
Figure 1. Author testing and perfecting the questionnaire in 2004 on dermatology patients at the University
of Miami Miller School of Medicine.

410 JOURNAL OF COSMETIC SCIENCE
Unlike most skin typing systems that focus solely on a single condition like dry or acne-
prone,22 the BST codifies an individual’s skin phenotype by considering multiple factors
simultaneously. This approach ensures that the skin care regimen is tailored to all of the
individual’s skin concerns—not just one—leading to improved and predictable outcomes.
SKIN TYPE QUIZ VALIDATION
The skin type quiz was validated using many methods and with collaboration among
dermatologists around the world. Validation studies of the latest quiz version are currently
being run in Indonesia, Portugal, and Africa. The original quiz had over 300 questions.
The next version was 64 questions. The latest version has 15 multiple response questions.
The questionnaire is constantly being tested, revalidated, and reformatted as worldwide
data are gathered, and as technology changes occur, such as the recent advances in AI
data analysis. The original validation included examination of 400 dermatology patients’
quiz data at the University of Miami, compared to their diagnostic CPT codes assigned
by a blinded dermatologist who did not have access to the quiz results. The quiz was
able to accurately predict the facial skin diagnosis. Over the years, with adoption of the
quiz by 100 dermatology practices, it has shown to accurately reflect the corresponding
dermatologic diagnosis. All of the validation studies are out of the scope of this article, but
many are listed in the references.
SKIN TYPE CATEGORIZATION COMBINING MULTIPLE PARAMETERS
The BSTI categorizes individuals into 16 distinct skin phenotypes. These are further
subdivided into four sensitive skin subtypes.
The 16-skin type classification is based on four primary parameters or “barriers to skin
health”: dehydration, inflammation, uneven pigmentation, and risk of skin aging (Figure 2).
Each skin type is represented by a combination of these parameters and is assigned to a skin
type octagon that has a corresponding color and number, making it easy for individuals
to remember their skin type. The octagons can be placed on product images, so that the
consumer can shop by skin type, and on product reviews so they will know whose advice is
applicable to their skin type (Figure 3).
Figure 2. The four barriers to skin health are dehydration, inflammation, pigmentation, and aging. An
effective skin care routine should target all relevant barriers rather than just one. The presence or absence of
the barriers in each quadrant represents the skin type visually, as seen in Figure 3.