Nonsurgical skin care and rejuvenation
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| Plastic Surgery Volume2 - Aesthetic Surgery |
SYNOPSIS
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Acne
Determining skin type
Fitzpatrick skin phototype
Dr. Thomas B Fitzpatrick first introduced his approach to categorizing skin type, now known as the Fitzpatrick skin phototype (SPT) system, in 1975 in order to evaluate a patient’s response to ultraviolet (UV) exposure in preparation for treating psoriasis with light.1 In this system, patients are assigned a skin type based on their reported ability to tan or burn. A minimum erythema dose (MED) is identified for each skin type, which the practitioner then uses as a guide for selecting doses of UV therapy for various skin conditions. Of note, this skin-typing system has evolved into a method for characterizing a patient’s skin color. Currently, dermatologists may assign an SPT to a patient based on a clinical assessment of skin color and not necessarily after questions regarding the patient’s history of sun tanning or burning (Table 2.1). The Fitzpatrick SPT system originally included skin types I–IV and categorized only white skin. Naturally dark pigmented skin is typically labeled as SPT IV–VI. When category V was first added, it was used to describe all skin of color (brown or dark-brown skin). The SPT VI designation was later added to classify further skin of color.2 The correct use of the Fitzpatrick SPT is not an indicator of a patient’s ethnicity or interpretation of an individual’s skin color and complexion, but a measure of the skin’s potential to burn or to tan.
Although the Fitzpatrick SPT is widely accepted and used in dermatology, the system does not fully address certain issues related to individuals with darker skin types. For instance, some authors have questioned the potential to predict a patient’s MED based on reported ability to tan and burn. In fact, a poor correlation was observed between SPT, as obtained by self-reported tanning history, and MED in a study involving white patients. This study did reveal a better correlation between MED and skin complexion traits such as eye and hair color, freckling tendency, and number of moles.3 A poor correlation between SPT, based on self-reported tanning history, and MED has also been found in various studies in Asian and Arab skin.4–7 The authors of these studies have suggested that the SPT system is not applicable to nonwhite patients or the full range of ethnic backgrounds.
Another issue with the SPT system pertains to the correlation of visually assessed skin color with MED. Many dermatologists assign a Fitzpatrick SPT to a patient based on a clinical assessment of skin color, and rarely question a patient on skin-tanning history. Further, some authors have contended that SPT (as determined by observed skin color) does not correlate with the MED in ethnic skin. Specifically, they have suggested that, in skin of color, the constitutive pigment does not correlate with MED, as implied by the current conventional application of SPT.
For example, patients of African descent are typically labeled as having Fitzpatrick SPT V (brown) or VI (dark brown). However, it has been discovered through questioning that some of these patients have reported that they do frequently burn. If categorized based on self-reported tanning history, a subset of such patients likely would be classified as having SPT III or IV. In a study that compared skin pigmentation as measured by diffuse reflectance spectroscopy of MEDs, investigators found that epidermal pigmentation was not an accurate predictor of skin sensitivity to UVB radiation.9 These data illustrate some of the limitations of the SPT, which was originally designed to assess lighter skin types. Although the Fitzpatrick SPT remains in wide use, several other systems have been created in an attempt to depict skin type more accurately.
Baumann skin-typing system
The author has developed the Baumann skin-typing system (BSTS) in order to recognize a wider range of cutaneous variables. Four skin parameters are assessed: (1) oily versus dry; (2) sensitive versus resistant; (3) pigmented versus nonpigmented; and (4) wrinkled versus tight (unwrinkled). These four spectra are not mutually exclusive; therefore, assessing the skin using all four parameters yields 16 potential skintype permutations (Table 2.2).
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| Baumann skin-typing system |
The BSTS provides specific guidance to identify the most suitable skin products for individuals, and also to help standardize the discussion of skin care science. The BST is easily determined by a scientifically validated questionnaire known as the Baumann skin type indicator (BSTI), which is used to identify baseline skin type10 (questionnaire available at no charge at www.skintypesolutions.com). Doctors and aestheticians can use this information to help identify the products and procedures most suitable for their patients. The remainder of this chapter will discuss skin care science following the format of the BSTS.
Dry skin, or xerosis, is characterized by an impaired barrier, lack of natural moisturizing factor (NMF), or reduced sebum production. Conversely, oily skin is characterized by elevated sebum production. In the BSTS, a higher score indicates increased sebum production, while a low score corresponds to diminished skin hydration. A person with a BSTI score in the middle of this parameter is considered to have “normal” skin. It is possible for a person to vacillate between oily and dry skin with climate change. These skin types are known as “combination.”
Characterized by inflammation, sensitive skin manifests as acne, rosacea, burning and stinging sensations, or skin rashes. Higher scores in the “S” portion of the BSTI suggest a greater likelihood that the patient exhibits several types of sensitive skin. For instance, a patient who has symptoms of burning and stinging as well as rosacea would have a higher “S” score than a patient with rosacea only. A robust stratum corneum (SC) is typical of someone with resistant skin, which protects the skin from allergens, other environmental irritants, and water loss. Erythema and acne are rare in people with resistant skin. Stronger skin care products and in-office procedures such as chemical peels can be more safely used on patients with resistant skin than on those with sensitive skin.
The pigmented/nonpigmented parameter refers to neither skin color nor ethnicity. Rather, this designation focuses on the propensity for skin to develop hyperpigmentation under certain stresses. Examples include a history of solar lentigines, melasma, and freckles. In this system, individuals with darker skin types are more likely to be categorized as having the pigmented skin type, while individuals with light skin who do not tan easily are often categorized as the nonpigmented skin type. Knowing a patient’s “P” score can alert the physician to a patient’s pigmentary changes and provides helpful data for the practitioner to consider when adjusting chemical peel strengths and laser settings to prevent the development of postinflammatory hyperpigmentation.
Skin aging
The manifestation of cutaneous aging is a result of the complex interplay between intrinsic and extrinsic factors. Intrinsic aging is attributed to individual heredity and the natural effects of the passage of time and, as such, is considered inevitable and beyond voluntary control. Extrinsic aging occurs as the result of exogenous insults, such as exposure to UV radiation, cigarette smoke, other pollution, as well as poor nutrition, and, by definition, can be avoided. Premature skin aging is evidence of extrinsic aging. In fact, 80% of facial aging is attributed to solar exposure alone.11
At a cellular level, UV exposure leads to skin damage through numerous mechanisms, including sunburn cell formation, thymine dimer development, collagenase production, and engendering an inflammatory response. These lead to photoaging, photocarcinogenesis, and photoimmunosuppression. 12 Interestingly, a recent paper suggests that the photoaging and melanogenesis provoked by UV exposure are linked to telomere-based DNA damage signaling that may represent a cancer avoidance protective response.13 Telomeres, specialized chromosomal components, shorten with age; telomeric loss or erosion has thus become an important measure of cellular aging, a veritable internal aging clock.14 The enzyme telomerase, which stabilizes or lengthens telomeres, is expressed in about 90% of all tumors but absent in many somatic tissues.15 One of the few regenerative tissues to express telomerase, however, is the epidermis.16 Telomerase is
believed to act against excessive telomere loss in human epidermis throughout the lifelong regeneration process.17 Interestingly, exposure to UV radiation, due to its deleterious effect on DNA and its acceleration of telomere shortening, can be characterized as influential in intrinsic as well as extrinsic aging. Signaling through p53 after telomere disruption is also typically observed in skin aging and photodamage.18 Currently, there are no skin care products available that target telomerase.
At the macroscopic level, the development of rhytides, caused by alterations in the dermal layer of skin, is the most prominent manifestation of cutaneous aging. Because few skin care product ingredients can sufficiently penetrate the dermis to ameliorate deep wrinkles, the prevention of rhytides is the focus of dermatologic antiaging skin care.19 Specifically, dermatologists aim to slow the degradation of or replenish the three main dermal constituents (collagen, elastin, and hyaluronic acid), all of which are known to decline with age. Reducing inflammation is key here, as inflammation can contribute to the breakdown of these structural components of the skin. Skin inflammation itself can result from the formation of free radicals, which can act directly on growth factor and cytokine receptors in keratinocytes and dermal cells. While the exact mechanisms of growth factors and cytokines in skin aging have not been fully understood, it has been established that they function together in a complex interplay involving several types of growth factors and cytokines.20 Better understood, however, is the influence of free radicals on the aging process. The activation of the mitogen-activated protein kinase pathways induced by free radicals has been shown to result in collagenase synthesis, paving the way for collagen degradation.21 Using antioxidants to inhibit this pathway is believed to prevent photoaging by thwarting collagenase production. In a study on human skin, Kang et al. demonstrated that pretreatment with the antioxidants genistein and N-acetyl cysteine hindered the UV induction of the cJun-driven enzyme collagenase.22 Vitamins C and E, ferulic acid, coenzyme Q10, green tea, pycnogenol, silymarin, and idebenone are among the various antioxidants featured in multiple skin care products.
Dry skin
The relative lack of moisture in the SC is indicative of xerosis, or dry skin, which is characterized by cracks and fissures when the level of water, the primary plasticizer of the skin, is low.23 Water content in the SC must be at least 10% in order for the skin to appear and feel normal.24 The elevation in transepidermal water loss (TEWL) that progresses to xerosis occurs when a defect in the permeability barrier permits the loss of excess water to the atmosphere. The etiology of the barrier perturbation itself is generally multifactorial and includes variables such as harsh detergents, acetone, and other contactants, as well as frequent bathing (Box 2.1).
Dry skin can also be engendered by changes in the epidermal
lipid component of the skin. The incidence of dry skin
is suspected by some dermatologists to have increased in
recent years, a phenomenon that has been attributed to
increased bathing and showering using hot water, foaming
cleansers, fragranced bubble baths, and bath salts, all ofwhich can denude the skin of lipids, thus impairing barrier
function. In fact, soap, detergents, and hard water all have
the capacity to wash off the healthy and normal barrier of
the skin.
Underlying disease is not the root cause of the majority of
dry-skin complaints. Most patients simply lack the ability to
cope with environmental elements that adversely affect the
water-binding capacity of the SC (see Box 2.1 for environmental
factors that can cause dry skin). Dry skin is more likely to
occur during the fall and winter months due to lower humidity
as well as excessive bathing in hot water. The condition
also increases with age, as skin tends to become less oily.
Indeed, xerosis has been referred to as “winter itch” because
it is at its worst during that season. The areas of the body most
often affected are those with comparatively few sebaceous
glands, such as the arms, legs, and torso.
Clinical signs
Initial clinical signs of xerosis include a dull gray-white color
and increased topographical skin markings.25 With increased
dryness, TEWL spurs a degradation in the cohesiveness
between the corneocytes, while resulting in an abnormal
retention of desmosomes. The loss of cohesiveness in entire
sheets of corneocytes manifests in scaling, flaking, and an
overall rough cutaneous texture. The resultant appearance of
the skin is dull because a rough surface is less able to refract
light than a smooth surface. The skin is then less pliable with
stretching and bending; diminished elasticity can then yield
visible cracks and fissures.
Basic skin care formulations
Xerotic symptoms can be treated by increasing the hydration
state of the SC with occlusive or humectant ingredients and
by smoothing the rough surface with an emollient. Moisturizers
are designed to increase cutaneous hydration. Most moisturizers
are oil-in-water emulsions, such as creams and lotions,
or water-in-oil emulsions such as hand creams. While moisturizers
are intended to enhance the hydration state of the
SC, moisturizing ingredients operate in discrete ways.
Occlusives coat the SC and retard TEWL; humectants draw
water from the atmosphere as well as the underlying epidermis,
thus hydrating the skin; and emollients soften and
smooth the skin. Practitioners should understand the distinct
categories of moisturizing ingredients and how various individual
and combination products work. Toners were invented
to remove the soap scum of cleansers. Modern cleansers do
not leave this film in most cases (and when they do, it is disastrous)
so toners are not really necessary in a skin care line.
Cleansing agents are used by people of all skin types. Brief
primers on cleansing agents and moisturizing agents follow.
Cleansers
Surfactants are the main active ingredients in cleanser products.
They regulate the degree of mildness or irritancy of a
formulation. Most surfactants in cleansers are anionic, because
of their ideal foam and lather qualities.
Bar surfactants
Soap (alkyl carboxylate), the primary surfactant in most
cleansing bars, is usually produced by saponification, involving
a reaction of a triglyceride oil/fat with an alkali. Vegetable
oils (e.g., palm oil, palm oil derivatives, rice bran oil, ground
nut oil, and castor oil combined with coconut oil or palm
kernel oil) are typical.26 Nonvegetable ingredients in soap
typically come from animal fat (e.g., tallow). Despite their
effectiveness as cleansers, soaps can irritate the skin, causing
erythema, xerosis, and pruritus, especially in cold weather.27
Newer classes of soaps (i.e., superfatted soaps, transparent
soaps, and combination bars) have been developed to provoke
less irritancy.
Superfatted soaps
Superfatting is intended to enhance the mildness, moisturization,
lather, mush value, and wear rate of a soap.28–30 This is
achieved through incomplete saponification (neutralization)
by leaving unreacted fatty acids or oils in the soap or
by adding fatty alcohols, fatty acids, or esters during
production.
Transparent soaps
Manufacturing with a high level of humectants intended to
solubilize the soap renders a transparent, clear appearance.
Transparent soaps contain high levels of active soap and an
alkaline pH, qualities that typically cause irritancy. These
products are usually mild, however, due to the presence of
the humectant glycerin and low levels of fatty acids.31
Combination bars
Combination bars (combars) combine natural soaps with
milder synthetic surfactants. The pH of these products is in
the high range (9.0–9.5), but the synthetic surfactants seem to
inhibit irritancy, leaving these products less likely to cause
irritation as compared to average soaps.32
Synthetic detergent bars
Unlike soaps, synthetic detergent bars (syndet bars) are
created through esterification, ethoxylation, and sulfonation
of oils, fats, or petroleum products, and are formulated in the
neutral-pH range. Alkyl glyceryl ether sulfonate, alpha olefin
sulfonates, betaines, sulfosuccinates, sodium cocoyl monoglyceride
sulfate, and sodium cocoyl isethionate are among the
synthetic surfactants used in such bars.33 The most commonly
used synthetic surfactant is sodium cocoyl isethionate, which
confers mildness on these products.
Liquid surfactants
Anionic and amphoteric surfactants are often combined in
liquid cleansers. Soaps (salts of fatty acids) and synthetic surfactants
such as alkyl ether sulfate, alkyl acyl isethionates,
alkyl phosphates, alkyl sulfosuccinates, and alkyl sulfonates
are the anionic surfactants regularly used in these products.
The common amphoteric or zwitterionic surfactants used are
cocoamido propyl betaine and cocoamphoacetate. Nonionic
surfactants (e.g., alkyl polyglucoside) and amino acid-based
surfactants (e.g., acyl glycinates, alkyl glutamates, and sarcosinates)
are increasingly used as the main surfactants in
liquid cleansers because they enhance mildness. Most liquid
cleansers have a pH in the neutral to acidic range; however,
the products that contain soap (alkyl carboxylate) as the chief
active ingredient usually have an alkaline pH (Box 2.2).
Moisturizers
Moisturizers increase water content in the SC by preventing
water evaporation (TEWL) from the skin with the use of
occlusive ingredients or by increasing the integrity of the skin
barrier. The primary method of increasing the integrity of the
skin barrier is delivering fatty acids, ceramides, and cholesterol
to the skin and controlling the calcium gradient. Assisting
the skin to hold on to water is another moisturization
approach, achieved by increasing levels of NMF, glycerol
(glycerin), and other humectants such as hyaluronic acid.
Enhancing the ability of the epidermis to absorb important
components for the circulation, such as glycerol and water
through aquaporin channels, also augments skin hydration
(Box 2.3).
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| Plastic Surgery Volume2 - Aesthetic Surgery |
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