Cosmetics



Cosmetics


John S. Barbieri, MD, MBA

Caroline A. Nelson, MD,

Sherry H. Yu, MD



Cosmetics and Cosmeceuticals


Basic Concepts



  • Chronologic aging and photoaging each contribute to change in human physical appearance over time. A simple systematic tool is the Glogau photoaging classification— wrinkle scale (Table 9.1).


  • Cosmetics and cosmeceuticals are topicals with desirable aesthetic effects. Cosmeceuticals are scientifically designed and meet rigid chemical, physical, and medical standards.


Clinical Applications


Cosmetics



  • Cleansers, moisturizers, and astringents are the three primary categories of skin care products.


  • Cleansers remove sebum, desquamating corneocytes, pathogens, and dirt while leaving the intercellular lipid barrier intact.



    • Soap: long-chain fatty acid alkali salts in a bar that alkalinize the skin, leading to disruption of the stratum corneum and the feeling of tightness after washing.


    • Syndet (synthetic detergent): “beauty cleanser” in a bar or liquid that contains <10% soap and has a pH of 5.5 to 7.0.


    • Combar: combination of soap and syndet in a bar.


    • Body wash: combination of syndet and moisturizer in an emulsion system applied with a puff.


    • Lipid-free cleanser: may contain cetyl alcohol, glycerin, propylene glycol, sodium lauryl sulfate, or stearyl alcohol.


    • Cleansing cream: waxes and mineral oil with detergent action from borax.


    • Exfoliant cleanser: contains glycolic acid or salicylic acid.


    • Abrasive cleanser: syndet with small particles (eg, polyethylene beads).









  • Gentle cleansers (eg, syndets, lipid-free cleansers, and cleansing creams) that are fragrance-free may be preferred by patients with eczematous dermatitis or xerosis. Exfoliant cleansers may be preferred by patients with acne.


  • Moisturizers retard TEWL and facilitate restoration of the stratum corneum barrier through occlusion and humectancy. Petrolatum, the most effective occlusive moisturizer, reduces TEWL by 99%. Other types of moisturizers include cream, polymer-based, vegetable oil and wax, glycerin-rich, dimethicone and ceramides. Humectants (eg, glycerin, HA, propylene glycol, urea) attract moisture. Urea is a keratolytic FDA-approved for hyperkeratotic conditions.



    • Occlusion and humectancy work hand in hand, since water drawn by a humectant to the stratum corneum will be lost to the atmosphere unless trapped by an occlusive.


  • Astringents (toners) are applied after cleanser and before moisturizer. Oily complexion astringents are formulated to remove sebum or deliver keratolytics. Dry complexion astringents are formulated to deliver humectants or skinsoothing agents.



    • Toners “tone down” deficiencies in cleansers and moisturizers.



  • Facial foundations can add or blend color, camouflage pigmentation irregularities, normalize facial skin tone, provide photoprotection, and act as a treatment product.


  • Facial powders can be used to prevent migration of foundation, add photoprotection, and absorb oil. Facial blushes and eye shadow can be used to add color.


  • Mascaras are designed to color, camouflage, elongate, and thicken the eyelashes.


  • Lipsticks are designed to add color. “Lip plumpers” cause transient edema due to irritants (eg, capsaicin).


  • Pigmentation defects can be camouflaged with a cosmetic that is opaque or complementary in color (eg, green undercover foundation for patients with rosacea).


  • Contour defects can be camouflaged with artistic shading based on the principle that dark colors make protuberances appear to recede and light colors make depressions appear more shallow.


  • Hair care products include shampoos that cleanse the hair and conditioners that reverse hair damage.


  • Nail care products include nail polish and nail sculptures (artificial nails).


Cosmeceuticals



  • α-Hydroxy acids include monocarboxylic acids (glycolic, lactic, mandelic), dicarboxylic acids (malic, tartaric), and tricarboxylic acids (citric). These acids thin the stratum corneum and decrease melanogenesis in the epidermis as well as stimulate synthesis of GAGs and collagen in the dermis. They are commonly used in the management of acne and photodamage.


  • β-Hydroxy acids include salicylic acid, which enters the pilosebaceous unit and is comedolytic and keratolytic (possibly by disrupting desmosomes). Salicylic acid is FDAapproved for acne, calluses and corns, dermatitis, hyperkeratotic skin disorders, psoriasis, seborrheic dermatitis, and warts.


  • Antioxidants include carotenoids (eg, retinol), flavonoids (eg, silymarin), polyphenols (eg, green tea), and endogenous antioxidants (eg, vitamins B3, C, and E). Epigallocatechin gallate, a green tea polyphenol, is the major ingredient of sinecatechins, which are FDA-approved for condyloma acuminata.


  • Anti-inflammatories include aloe vera.


  • Pigment lighteners include kojic acid (inhibits tyrosinase activity) and vitamin C.


  • Cosmeceuticals used to diminish ecchymoses include arnica, bromelain, and vitamin K.


Safety Considerations



  • Cosmetics and cosmeceuticals (eg, urea, propylene glycol, α-hydroxy acids, β-hydroxy acids, sinecatechins) may cause ICD.



    • Salicylism has been reported after topical salicylic acid use in infants.


  • Cosmetics and cosmeceuticals may also cause ACD. Common culprits include triclosan, a previously popular antiseptic in cleansers now banned by the FDA, paraphenylenediamine (PPD) in permanent hair dyes, and tosylamide formaldehyde resin in nail polish.


  • Polyethylene beads in abrasive cleansers may contribute to the microplastics detected in human stool and, ultimately, to environmental pollution.



    • Globally, humans ingest ˜5 g of plastic every week, the equivalent of a credit card.


  • Facial powders typically contain predominantly talc. Application of talc to the genital area has been associated with ovarian cancer; however, data are inconclusive.


  • Liquid mascara contaminated with bacteria can lead to infection. Tubes should be discarded after 3 months and should not be shared. Mascara may also cause conjunctival pigmentation.


Chemical and Mechanical Skin Resurfacing


Basic Concepts



  • Ablative skin resurfacing involves controlled injury of the skin to a specific depth to promote the growth of new skin with improved surface characteristics. The three primary categories are chemical, mechanical, and laser resurfacing. For laser resurfacing, see Chapter 9: Lasers.


  • Chemical resurfacing is accomplished with chemical peels (Table 9.2). The degree of frosting correlates with depth:



    • Level I: Erythema with blotchy frosting;


    • Level II: White-coated frosting with patchy erythema showing through;


    • Level III: Solid white enamel frosting.


  • Mechanical resurfacing may be superficial (eg, microdermabrasion, microneedling), medium-depth (eg, conservative manual dermasanding), or deep (eg, aggressive manual dermasanding, wire-brush or diamond-fraise dermabrasion). Microdermabrasion propels a rough substance (eg, aluminum oxide crystals) at the skin while simultaneously removing it with suction. Microneedling uses multiple fine needles to cause a superficial injury to the skin.


  • Cleaning and degreasing the face is important prior to resurfacing to create a smoother and more regular surface that will enable better control over depth of the procedure.


Clinical Applications



  • Indications for skin resurfacing include melasma, acne (limited evidence), multiple pre-neoplastic or neoplastic epidermal lesions, scarring, and photoaging.


  • Skin resurfacing for melasma is more effective for epidermal than dermal melanin and is often combined with hydroquinone.


  • Medium but particularly deep peels can stimulate new collagen production.


  • While TCA concentrations ≥40% are not recommended, high TCA concentrations (>70%) can be used for focal chemical reconstruction of acne scars via the TCA Chemical Reconstruction Of Skin Scars (TCA CROSS) technique.










Safety Considerations



  • Complications from chemical peels include:



    • Ocular exposure: Sodium bicarbonate is used to neutralize glycolic acid, saline is used to dilute TCA, and mineral oil is used to dilute Baker-Gordon phenol solutions.


    • Pigmentary changes: Postoperative photoprotection is critical. Salicylic acid has the lowest risk of postinflammatory hyperpigmentation and is safe in all skin phototypes. Phenol may cause permanent hypopigmentation.



      • Phenol peels may result in an “alabaster” or “plastic” appearance.


    • Persistent erythema (>2 months): Consider massage, corticosteroids, silicone gel sheeting, and PDL therapy.


    • Delayed wound healing: Postoperative tobacco avoidance is critical. Abnormal healing may also occur in patients without intact pilosebaceous units (eg, history of radiation therapy). Pretreatment with topical tretinoin (2-4 weeks prior to resurfacing) improves penetration and decreases healing time; however, tretinoin should be held in the postoperative period until re-epithelialization is complete and erythema is diminished.


    • Scarring: Mechanical and laser resurfacing may be delayed for patients exposed to isotretinoin during the prior 6 months due to risk of abnormal scarring (controversial).


    • Infection: HSV prophylaxis for 10 to 14 days starting on the day of the procedure should be considered for superficial resurfacing in patients with a history of HSV and is required for medium-depth or deep resurfacing. Acetic acid soaks can decrease bacterial infections.



  • Phenol peels may cause cardiotoxicity (7% of patients will exhibit transient arrhythmias). History of cardiac arrhythmias or taking a medication known to precipitate arrhythmias are absolute contraindications; hepatic or renal disease are relative contraindications. IV hydration and monitoring (continuous ECG, pulse oximetry, blood pressure) are required.


Lasers


Basic Concepts



  • LASERs (Light Amplification by Stimulated Emission of Radiation) emit light that is monochromatic (single wavelength), spatially coherent (wavelengths are aligned in phase), and collimated (moves in parallel fashion).



    • The 3Cs of lasers are monochromatic, coherent, and collimated.


  • Laser parameters include:



    • Fluence: How much energy is delivered (typical units: J/cm2).


    • Spot size: Over what area is the energy delivered.


    • Pulse duration: How quickly is the energy delivered.







  • The wavelength of a laser is determined by the lasing medium: liquid (dye), gas (for example argon, krypton, carbon dioxide [CO2]), solid (eg, alexandrite crystal).


  • Major interactions between laser light and skin include absorption, reflection, scatter, and transmission.



    • Radiation is NOT a major interaction between laser light and skin.


  • At the interface between air and the stratum corneum (skin surface), 4% to 7% of light is reflected because of the difference in the refractive index between air (n = 0) and the stratum corneum (n = 1.45): Fresnel reflectance.


  • Between 308 nm (excimer) and 1064 nm (long-pulsed [Nd:YAG]), the depth of penetration increases as the wavelength increases. However, for longer wavelengths (for example 10,600 nm [CO2]), energy is absorbed primarily by the epidermis.


  • Larger spot sizes result in deeper energy penetration due to decreased scattering.


  • By targeting specific chromophores in the skin that absorb the energy (Figure 9.1), it is possible to selectively damage structures of interest while minimizing damage to surrounding tissue (selective photothermolysis). It is important
    for the chromophore to have high absorption relative to other chromophores at that particular wavelength to prevent off-target damage. For example, melanin has a strong absorption at 595 nm, but so does oxyhemoglobin. The PDL is therefore not ideal for hair removal because it will also target blood vessels. In contrast, melanin has strong relative absorption at 755 and 810 nm, which is why the alexandrite and diode lasers are preferable for hair removal.


  • The pulse duration should be less than or equal to the target chromophore’s thermal relaxation time (cooling time to lose 50% of heat), which is proportional to the square of the diameter of the target. Large targets such as a leg vein or hair follicle require a long pulse duration (ms), while small targets such as tattoo pigment granules are best targeted with a short pulse duration (ns, ps).







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Apr 2, 2025 | Posted by in Dermatology | Comments Off on Cosmetics

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