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Volume 37, Issue 3, Pages 16-17 (March 2006)
Helena Rubinstein is credited with classifying four different skin types during the early 1900s, and her classification has essentially gone unchallenged since that time.
Skin has thus been classified as dry, oily, combination, or sensitive, and the skin care-product market, which mushroomed into a billion-dollar industry in the past century, worked to match these skin types with increasing sophistication founded on well-funded research. Consumers are now bombarded with products and claims, some outrageous and some realistic, and, frankly, they are confused and don't know whom to believe.
I have developed a new skin typing system that will help consumers figure out what ingredients are right for them. This system will, I hope, lead to better consumer education and more educated product purchases. I also hope it will help dermatologists guide their patients toward efficacious products and save them from wasting money and time on unnecessary products.
Skin types can be best categorized on the basis of four parameters:
1. Dry or oily.
2. Sensitive or resistant.
3. Pigmented or nonpigmented.
4. Wrinkled or tight (nonwrinkled).
Combining these four parameters yields 16 possible skin types. For example, you could be a dry, sensitive, pigmented, and wrinkled type (DSPW), and would benefit from different skin care than would a dry, resistant, pigmented, and wrinkled type (DRPW).
The skin type is determined by a 64-item questionnaire that patients self-administer. It has been tested on thousands of patients and works for both genders, all age groups, and all ethnicities. The questionnaire results in a score for each of the four parameters. For example, a patient might have a high O score, which would indicate more skin oiliness than a medium O score.
This month's column will focus briefly on the basic science underlying the four parameters and the kinds of formulations best suited to particular skin types.
Skin Hydration: Dry (D) vs. Oily (O)
Skin that is dull gray-white in color, rough in texture, and characterized by an elevated number of ridges is considered xerotic or “dry” (J. Soc. Cosmet. Chem. 1976;65:376).
The stratum corneum of the skin is surrounded by a lipid bilayer composed primarily of ceramides, fatty acids, and cholesterol. When these constituents are present in the proper proportion, they form the “skin barrier,” which functions like a brick wall (keratinocytes) covered by mortar (the lipid bilayer). This barrier protects the skin and keeps it watertight.
Defects in the stratum corneum or barrier can result in transepidermal water loss, which dehydrates the skin and imparts a dry appearance. An impaired barrier may also make skin more susceptible to damage from exogenous sources such as plants, chemicals, and even water.
Although replenishing the three key components of the stratum corneum is the aim of some skin care formulations, diet also plays an important role in maintaining a healthy skin barrier, insofar as fatty acids and cholesterol are derived from the diet. Indeed, it is worth noting that individuals receiving cholesterol-reducing drugs exhibit dry skin.
Frequent eruptions of erythema and pruritus typify dry, sensitive skin (DS) and indicate a likely defect in the stratum corneum. People with such skin are at higher-than-average risk for eczema. The addition of evening primrose oil, borage oil, or omega fatty acids to the diet may contribute to ameliorating dry, sensitive skin by replenishing essential components of the stratum corneum.
Natural moisturizing factor (NMF), a substance that retains water inside keratinocytes and renders them plump, also plays an important role in the pathophysiology of dry skin.
NMF is derived from the hydrolysis of the protein filaggrin, which confers structural support to the dermal layers and breaks down as NMF in the epidermal layers, exhibiting a strong capacity to bind water and hold it inside the cell. The breakdown of filaggrin acclimates to varying environmental conditions over a course of several days, so in a low-humidity environment, more NMF is produced.
Although a deficiency of NMF can cause dry skin, it does not increase skin sensitivity. Low levels of NMF may play a role in the dryness seen in DR (dry, resistant) skin types. However, low sebum levels—as discussed later in this section—are likely to play a role as well.
Currently, there is no known method of artificially enhancing filaggrin breakdown in order to elevate NMF levels. In the 1970s, UV light was demonstrated to disrupt the enzymatic hydrolysis of filaggrin to NMF, suggesting that reduction of sun exposure might improve skin dryness.
Hyaluronic acid (HA), which can bind 1,000 times its weight in water, also helps retain water in the skin. Aged skin is characterized by reduced HA levels, which causes dryness and makes the skin appear older and less plump.
Glucosamine supplements may help increase HA production, and superficial injections of HA as mesotherapy serve to reduce wrinkles. It is important to note that HA does not penetrate the skin when applied topically (Cosm. Toil. 1998;113:35–42). HA deficiency does not increase skin sensitivity. Reduced HA levels are characteristic of DW (dry, wrinkled) skin types.
The reduced production of sebum also may play a role in dry skin. Sebum contains wax esters, triglycerides, and squalene, all of which protect the skin from the environment (Clinics Dermatol. 1995;13:307–21).
Sebum-derived fats form lipid films on the skin surface that help to prevent water loss. However, low sebaceous gland activity is not correlated with xerosis. In fact, not all people with xerosis have decreased sebum production, which is affected by diet, heredity, stress, and hormones (Br. J. Dermatol. 1988;118:393–6).
The influence of sebum on dry skin is not well understood (J. Invest. Dermatol. 1987;88:2s–6s). Most studies examining the role of sebum in dry skin have been performed on DS (dry, sensitive) skin types, such as those with atopic dermatitis, and not on DR (dry, resistant) skin types, which do not have a barrier dysfunction. More research needs to be done on DR types and the role of sebum.
Numerous products are available for treating dry skin. For DS types, I generally recommend formulations that include ceramides, fatty acids, and cholesterol, which help repair the impaired skin barrier. Available brands include Dove Sensitive Essentials, CeraVe, and Atopalm. For DR types, I recommend products containing both a humectant and an occlusive ingredient. Glycerin, safflower oil, and shea butter are some of my favorite ingredients for this skin type.
All patients with dry skin types should avoid foaming detergents and soaps—which are found in laundry cleansers, body cleansers, and face cleansers—and prolonged baths, particularly in hot or chlorinated water. They also should use humidifiers in low-humidity environments, take omega-3 fatty acid supplements, spray a facial water prior to applying moisturizer, and moisturize two or three times daily.
Individuals with slightly oily skin who straddle the threshold between sensitive and resistant have an ideal skin hydration scenario, insofar as such skin is typically characterized by an intact skin barrier, good NMF levels, and balanced sebum secretion. Such people rarely have acne; however, stress or hormonal fluctuations can lead to eruptions of acne in skin of this type. Slightly or very oily skin that is also sensitive is the type most prone to develop acne.
OS types fortunately can tolerate many of the products that DS types cannot. When elubiol—the only topical ingredient proved to reduce sebum production—was on the market, I recommended it to such patients. Now that it is no longer available, I suggest oil-hiding products, such as the polymer found in OC Eight by Ferndale Laboratories Inc. For women, foundation and powders that contain talc and other oil-absorbing ingredients can be helpful.
Skin Sensitivity: Sensitive (S) vs. Resistant (R)
Resistant skin rarely develops burning, stinging, rosacea, acne, or—unless the skin is sunburned—erythema. Individuals with resistant skin can typically use any kind of skin care product without incurring adverse reactions, but they may not benefit from them because many products are not potent enough to penetrate the stratum corneum and help conditions such as melasma, solar lentigines, and wrinkles.
More than 40% of people claim to have sensitive skin (Am. J. Contact Dermatitis 1993;4:108), a phenomenon that is self-reported most often by healthy premenopausal women and that appears to decline with age.
Sensitive skin is challenging to skin care-product manufacturers because there are four distinct types of sensitive skin: acned, rosaceous, stinging, and allergic. Before a patient with S-type skin can be adequately guided toward the appropriate skin care regimen, the specific type of sensitive skin must be ascertained. Inflammation is the common denominator among all sensitive skin types, however, and treatment focuses on lessening the inflammation and eliminating its cause.
Acne. Dermatologists know that this condition is associated with three primary pathophysiologic factors: elevated sebum production (O-type skin), clogged pores, and the presence of Propionibacterium acnes.
OS types are the ones most likely to develop acne. For patients with OS skin of the acne subtype, I recommend salicylic acid and benzoyl peroxide. If a patient also exhibits erythema, however, I suggest only the anti-inflammatory salicylic acid. Of course, many efficacious prescription antibiotic products and retinoids can also be used.
Rosacea. OS types with light skin—particularly those with the W (wrinkled) skin type who have a strong history of sun damage—have a greater likelihood of developing rosacea.
For OS patients with rosacea, I recommend products that contain feverfew (such as the Aveeno Ultra-Calming line), the anti-inflammatory quadrinone (such as in the Cutanix products), the licorice extract licochalcone (such as in the Eucerin Redness Relief products), or selenium (such as in Thermal Spring Water by La Roche-Posay).
For rosacea patients of the DS type who experience erythema and stinging, I recommend products containing sulfacetamide (such as Rosanil, Rosac, Rosula, and Avar). For patients with erythema and flushing, but no history of stinging on application of various products, I recommend azelaic acid (such as Azelex and Finacea).
Stinging. This subtype of sensitive skin is acknowledged less often than the acne and rosacea subtypes. Stinging, which is not an allergic phenomenon, is thought to result from increased neural sensitivity. Some people, known as “stingers,” respond to particular ingredients that other people cannot “feel.”
The lactic-acid stinging test assesses individuals who report invisible and subjective cutaneous irritation.
Both 5% and 10% lactic-acid preparations have been used to show that a subset of patients experience unpleasant or stinging sensations to the nasolabial fold (J. Soc. Cosmet. Chem. 1977;28:197; Contact Dermatitis 1998;38:311).
Although many rosacea patients who exhibit facial flushing are more likely to experience stinging to lactic acid (Acta Derm. Venereol. 1999;79:460–1), many patients who are stingers do not experience redness or visible skin irritation (Contact Dermatitis 1993;29:185–8).
I recommend that patients with S-type skin who are stingers avoid the following ingredients: benzoic acid, bronopol, cinnamic-acid compounds, Dowicel 200, formaldehyde, lactic acid, propylene glycol, quaternary ammonium compounds, sodium lauryl sulfate, sorbic acid, urea, vitamin C, and a-hydroxyl acids (particularly glycolic acid).
Allergic. Like the stinging-skin subtype, this category is acknowledged less often than the acne and rosacea subtypes. Patch testing can determine a patient's allergic responses to cosmetic ingredients. Studies have demonstrated that up to 10% of dermatologic patients who are patch tested are allergic to at least one cosmetic product ingredient (Am. J. Clin. Dermatol. 2004;5:327–37). This finding likely underrepresents allergic response, given that most patients who experience reactions to newly purchased cosmetics rarely consult a physician. Patients between 20 and 60 years old account for roughly 80% of reactions, with a majority reported by women (Int. J. Dermatology 2003;42:533–42).
Fragrances and preservatives are the two most common of the allergens. The greater the exposure to ingredients, in number and over time, the greater the likelihood that an individual will display or develop an allergy to the ingredients.
Patients with an impaired stratum corneum, manifested by dry skin, are more likely to experience allergic reactions to topically placed allergens (Med. Pregl. 2004;57:209–18). Therefore, most patients with S-type skin who complain of frequent skin allergies also fall into the D-type skin category. DS types are more prone to develop eczema and allergic reactions to topical products.
In addition to the anti-inflammatory ingredients mentioned above for acne and rosacea, I recommend nonfoaming cleansers and barrier-repair moisturizers to these patients.
Skin Pigmentation: Pigmented (P) vs. Nonpigmented (N)
This parameter refers to the tendency to develop unwanted dark spots on the face or chest (for example, melasma, solar lentigines, and ephelides). This parameter does not refer to ethnicity. A red-haired white person with freckles is considered to be a pigmented type, as is an African American person with melasma or other unwanted dark spots.
The removal of hyperpigmentation is believed to represent the purpose of 21% of visits to the dermatologist, and more than 80,000 people annually buy over-the-counter skin care products to reduce or eliminate facial dyspigmentation.
P-type skin is often associated with the W (wrinkled) type in lighter-skinned individuals because of the association of solar exposure with wrinkling and solar lentigines. However, patients with darker skin often have PT (pigmented, tight) skin types because they have less of a tendency to wrinkle.
For P-type skin, I recommend products that contain hydroquinone, kojic acid, arbutin, Tyrostat, and mulberry extract. Patients with ORPW- and DRPW- type skin can also use vitamin C and retinoids.
To prevent recurrence of the dark spots, I recommend products containing soy (such as the Aveeno Positively Radiant line and Neutrogena Visibly Even products) or products with niacinamide (such as Olay Regenerist, Olay Total Effects, and Niadyne products).
Skin Aging: Wrinkled (W) vs. Tight (T)
Although an individual's behavior can influence the development of hyperpigmentation, the wrinkled/tight parameter is the only skin-type parameter within a person's control.
That is to say, whereas the genetic component of skin aging is apparently unalterable, individuals can reduce their risk of inducing or accelerating extrinsic aging, which results from factors such as smoking, poor nutrition, and, primarily, exposure to the sun. Indeed, 80% of facial aging is attributed to solar exposure (N. Engl. J. Med. 1997;337:1463–5).
Few skin products can penetrate deeply enough into the dermal layers, where wrinkles originate, to ameliorate the wrinkled appearance. However, several studies have demonstrated effectiveness in improving wrinkles, with two (Renova and Avage) receiving Food and Drug Administration approval for this indication. Antiwrinkle formulations aim to reduce inflammation and to slow or stop the loss of the skin's primary structural components (collagen, elastin, and hyaluronic acid).
For W types, I recommend antioxidants such as idebenone (found in Prevage), ferulic acid (found in SkinCeuticals CE Ferulic), vitamin C (such as the La Roche-Posay product Active C), or mushroom extract (found in Dr. Andrew Weil for Origins Plantidote Mega-Mushroom Face Serum).
I also recommend the use of an oral antioxidant such as Polypodium leucotomos extract (found in Heliocare) or pomegranate (found in Murad Pomphenol Sunguard Supplement).
In addition to that, all W types should be using a prescription retinoid.
For SW (sensitive wrinkled) skin types, I suggest Differin, which may be better suited to sensitive skin. For OW skin types, I suggest a gel retinoid, and for DW types, a cream retinoid.
Tailor the Treatment
When choosing skin care products for a patient, consider the 16 skin-type permutations. For example, an OSPW would do well with salicyli c acid because it would help clear sebum-clogged pores, decrease acne and inflammation, help exfoliate to speed removal of dark spots, and aid in retexturizing the fine wrinkles. A DRPW and ORPW would do very well with high concentrations of retinoids, which help ameliorate pigments and wrinkles; however, the DRPW would need a barrier-repair moisturizer, whereas the O type would not. I recommend glycolic acid for DRPW types, but I prefer salicylic acid for ORPW types.
When we consider the various manifestations of skin proclivities and are able to classify them in a more systematic manner than was allowed by previously established methods, we come closer to matching skin care recommendations to particular patient skin profiles.
To get more information, see my book “The Skin Type Solution” (New York: Bantam Dell, 2006).
DR. BAUMANN is director of cosmetic dermatology at the University of Miami. To respond to this column, or to suggest topics for future columns, write to Dr. Baumann at our editorial offices via e-mail at firstname.lastname@example.org.
© 2006 Elsevier Inc. All rights reserved.