411 AI-Guided Skin Care
THE PARAMETERS DEFINING BSTS
Oily Versus Dry. Oily skin in the Baumann Skin Typing System (BSTS) is characterized by
sebum production rates of at least 1 mg of sebum per 10 cm2 every 3 hours.23 The occlusive
properties of sebum compensate for an impaired barrier and contain antioxidants.24 In the
BSTS, oily skin is the preferable type. Normal skin falls into this category. The way that
normal, oily, and very oily skin are scored by the BSTI for skin care recommendations is
beyond the scope of this article.
Dry skin has dehydration and a defective barrier, and it lacks sufficient sebum to provide
enough occlusion to overcome this barrier.
A combination skin type is not considered a true skin type in the BSTS. People who self-
identify as combination skin types are one of two possibilities:
• Changing skin type: Some patients experience seasonal variability in their skin type,
with their BST alternating between dry and oily, depending on environmental factors
such as humidity and temperature.
• Oiliness in the T-zone: When there is excessive sebum production in the T-zone and
dryness on the cheeks, the BSTS classifies this as an oily skin type. This is considered
a “normal oily skin type,” and the skin should be treated with a skin care regimen
targeted to oily skin. The moisturizer in the skin care routine is not used in the T-zone
parts of the face that have more sebaceous glands.
Sensitive Versus Resistant. The BSTS divides sensitive skin into four subtypes based on
their propensity to inflammation from different causes. A resistant skin type, on the other
hand, does not have acne, inflammation, or a history of reacting to skincare products. An
individual can be classified as one sensitive subtype or a combination of subtypes.
Figure 3. An illustration of the16-skin type octagons and which barriers to skin health they represent. Note
that skin type 10 has no barriers to skin health. The use of these images is trademarked and cannot be used
without written permission.

412 JOURNAL OF COSMETIC SCIENCE
These are the four sensitive skin subtypes:
• Acne type (papules, pustules).
• Rosacea type (erythema).
• Stinging or burning.
• Allergic.
Pigmented Versus Nonpigmented. In the BSTS, the term “pigmented skin” is a skin type that
needs skin lightening ingredients in its skin care routine due to uneven skin pigmentation. It
does not refer to an individual’s base skin color or Fitzpatrick skin type. Instead, it specifically
denotes the presence of unwanted hyperpigmentation. It is important to note that the
designation of a nonpigmented skin type does not necessarily mean the person does not have
melasma, dark spots, or freckles. A nonpigmented type means the subject does not want to
lighten spots on the skin. This approach underscores the importance of considering patient
preferences in assigning a BST, as opposed to relying solely on camera imaging, which may not
adequately capture the nuances of an individual’s skin concerns and desired skin outcomes. The
pigmented designation does not imply that the patient has a higher risk of postinflammatory
hyperpigmentation. It just signifies that unwanted dyschromia is currently present on the face,
the subject wants to lighten it, and skin lighteners should be in the skin care routine. When
the hyperpigmentation clears, the subject changes to a nonpigmented skin type.
Wrinkle-Prone Versus Tight. Aging skin for the BSTS is defined as age over 30 or habits such
as sun exposure that increase the risk of skin aging. Wrinkle-prone skin types are assigned
ingredients in their routine to lower the risk of skin aging or to treat wrinkles, depending
on the person’s questionnaire responses to the questions about lifestyle habits. In an analysis
of more than 100,000 skin type quizzes, over 50% of individuals between the ages of 20
and 29 had lifestyle habits that warranted increasing antioxidants, DNA repair enzymes,
retinoids, and other protective and repair ingredients into the skin care routine. The tight
skin types are under the age of 30 with minimal sun exposure and healthy habits. The
tight designation indicates younger or well-maintained skin.
The 16-skin types listed in Table I are derived by combining these 4 dichotomous
parameters. The benefit of using the BSTS to build a custom skin care routine is that it
Table I
List of 16 BSTs
Skin Type 1- DSPT – Dry, sensitive, hyperpigmentation, tight
Skin Type 2- DSNT – Dry, sensitive, no hyperpigmentation, tight
Skin Type 3- DSPW – Dry, sensitive, hyperpigmentation, wrinkle-prone
Skin Type 4- DSNW – Dry, sensitive, no hyperpigmentation, wrinkle-prone
Skin Type 5- OSPT – Oily, sensitive, hyperpigmentation, tight
Skin Type 6- OSNT – Oily, sensitive, no hyperpigmentation, tight
Skin Type 7- OSPW – Oily, sensitive, hyperpigmentation, wrinkle-prone
Skin Type 8- OSNW – Oily, sensitive, no hyperpigmentation, wrinkle-prone
Skin Type 9-OPRT – Oily, resistant, hyperpigmentation, tight
Skin Type 10-ORNT – Oily, resistant, no hyperpigmentation, tight
Skin Type 11- ORPW – Oily, resistant, hyperpigmentation, wrinkle-prone
Skin Type 12- ORNW – Oily, resistant, no hyperpigmentation, wrinkle-prone
Skin Type 13- DRPT – Dry, resistant, hyperpigmentation, tight
Skin Type 14- DRNT – Dry, resistant, no hyperpigmentation, tight
Skin Type 15- DRPW – Dry, resistant, hyperpigmentation, wrinkle-prone
Skin Type 16- DRNW – Dry, resistant, no hyperpigmentation, wrinkle-prone