exfoliating

Exfoliating in skin care

Skin is an omnipotent barrier between the human body and the outer world.  The largest organ of the human body, skin covers the entire body surface and is responsible for several vital functions: protection (chemical & physical), sensation, thermoregulation, excretion and storage. Skin structures protect not only the outer body but also the internal organs through a specific tissue called epithelia. The skin major layers are epidermis – the external layer mainly composed out of keratinocytes that produce keratin and melanocytes that produce melanin – the skin pigment, dermis – mainly composed of fibroblasts, collagen and elastin acting as connective tissue and the skin supporting tissue called hypodermis – a fat cells and blood vessel base. Epidermis, the outermost skin layer, plays the most important role in the barrier function, acting against physical and chemical aggressions, and keratinocytes (90% out of the epidermis composition) are the main actors [1][2][3].
 
Keratinocytes are vital players in maintaining the barrier function against various environmental factors such as UVR, pathogens, chemicals, parasites and other environmental aggressors.  To successfully exercise all their function keratinocytes develop – via keratin production – a hard cellular wall that creates a physical protection shield against any invasion (stratum corneum, SC). Furthermore, once the shield is penetrated keratinocytes trigger a pre-inflammatory response and alerts the immune function. In order to successfully perform all their function and meet their responsibilities keratinocytes are constantly renewed by migration and differentiation of stem cells located in the basal (deep) epidermis. When a skin cell dies (apoptotic phase) it sheds from the skin surface in a process called desquamation and a new cell is already taking its spot. In humans, the complete keratinocytes turnover cycle takes about 40-50 days so in translation, every 40 days or so our skin’s outer layer is completely renewed [4][5].
 
Usually keratinocytes shedding, exfoliation or desquamation is a natural process that should take place without intervention. However, due to various environmental and intrinsic factors the fine balance of this process gets lost and the renewal rate and implicitly the barrier function are affected. Usually the phenomenon takes place in the most exposed body parts – face, neck, shoulders and back. Dead skin cell accumulation modifies the appearance of the natural, healthy skin into a dry, flaky, scale-like surface. To prevent this, from the oldest times, man turned to cosmetic procedures called exfoliations meant to remove apoptotic keratinocytes and make room for the new, freshly differentiated ones that migrate from the basal layer.
                                 
Exfoliation can be done mechanically – by topically scrubbing the area with an abrasive substance or chemically – and by using active ingredients that promotes and support the natural desquamation. Mechanical exfoliation is not suitable for sensitive or problematic skin, where its effects can be harmful and inflammatory. Commercial Chemical exfoliation products are usually aggressive and although they perform their task – removing the dead skin cells – they also leave behind an excessively dry surface that in time can lead to sebum imbalance and acne. However, through the means of DIY cosmetic a perfectly tailored exfoliating solution can be attained, one that will take care of all the skin particularities. Due to its active properties, the chemical exfoliate or peel performs beyond restoring the skin barrier. It also maintains healthy pores, eliminates blackheads, alleviates hyperpigmentation and acne scarring and last but not least it rejuvenates by reducing fine lines and wrinkles [6].
 
The chemically active ingredients are gentle, natural acids that work on removing the dry, inactive skin superficial layer without harming the epidermis.
 
Allantoin, a naturally occurring molecule both in animals and plants, is the final product of the nitrogen metabolism. Its acidity combined with the keratolytic activity (fight against abnormal keratinocytes proliferation) makes it a perfect exfoliating agent. When topically applied, allantoin exerts a mild aggression that will only involved the dead skin cells, aiding the desquamation process and helping the new cells migration and conserve the skin barrier. Even more, due to its antibacterial and anti-inflammatory properties mixtures containing allantoin also prevent against bacterial aggression and implicitly acne development [7].
 
Carnitine (L-carnitine, CA) is an active substance involved in cellular metabolism of glucose, fat and related compounds primarily used in cosmetic for its glycation inhibitor properties. L-carnitine is not only a mild yet potent chemical peel but also an effective sebum regulator and a cell proliferation promoter, helping the skin renewal process. This makes CA an excellent ingredient in topical chemical exfoliating mixtures, with multiple great benefits for the treated skin, especially in the diabetics, immuno-suppressed or other immune impaired conditions [8].
 
Creatine is an important substance synthesized in the human body, end vital in the energy metabolism, more precisely in energy regulation and flow. It is also an extensively used active for cosmetic treatments due to its high compatibility and excellent skin penetration, being associated with cell proliferation and migration, sebaceous gland regulation and wound healing support. Creatine’s more stable form, creatine pyruvate is an effective exfoliating agent, boosting natural kerationcytes shedding without being aggressive to the newly formed layer. Due to its multiple active actions it’s beneficial especially for sensitive, acne-prone and photodamaged skin [9].
 
Lactic Acid, the most potent of the alpha hydroxyl acids is another natural active extensively used in dermatology. Its acid ph as well as its other skin beneficial properties makes it a great candidate for DIY chemical peels. Topically use of lactic acid efficiently exfoliates the epidermal cells in the outermost layer of the skin, the stratus corneum (SC). Rough, scaled, tern and dull skin of the epidermis is peeled off and renewal of the SC is stimulated to refresh with a new layer of new keratin producing cells. Clinical studies have shown that lactic acid treatment can stimulate synthesis of lipids and ceramides in the skin which reinforce the skin resulting in more hydrated, supple, and bright skin [10].
 
Pumpkin bioferment is a potent enzyme exfoliating agent which aids the natural skin desquamation while nourishing the epidermis. Enzyme peels are superior to acid peels because they don’t modify the skin Ph, hence are even less aggressive than the acidic peels. The pumpkin peel has multiple positive effects on the treated skin: it stimulate cell dissemination and migration and implicitly boosts the skin renewal process, it cleans pores and eliminates blackheads and moisturizes the skin layers [11].
 
Salicylic Acid (Beta Hydroxy Acid) - a botanical active extracted from the seeds white willow bark - and the white willow bark extract (salicin) are famous for its benefits for the whole human body, from the omnipotent aspirin to topical salicin mixtures - efficient anti-inflammatory, antioxidant, and also great in regulating sebum production and maintaining clean, healthy pores. Both compounds are suitable for topical treatments for exfoliating, with positive impact on skin. Salicylic acid is lipid soluble and it mixes well with oily, greasy substances being excellent in exfoliating and moisturizing mixtures. This characteristic allows it to penetrate deep into pores and eliminate sebum blockages. This prevents the formation of blackheads, blemishes caused by dirt and oil becoming trapped under the skin. Because of its lipid solubility, salicylic acid is particularly useful for oily skin. As a natural source of salicylic acid, salicin extracted from the white willow bark is a natural and gentle exfoliation option for acne treatments that will cause no irritation [12][13].
 
Mild and gentle chemical exfoliation, especially for the face and acne-prone areas should be a part of a regular routine. Using the appropriate delivery vehicle – preferably moisturizing base creams and the best available active ingredients should improve the overall aspect of the skin. However, since most of the peels are acid it is important to start refining the best DIY exfoliating cream or gel from recommended recipes and then gradually modify quantities and add actives, in order to avoid any overdosing (improbable, with very mild second effects  such as temporary irritations, redness). Concluding, the best chemical peels are the ones that use top quality actives, delivered by top quality base products in a custom solution, perfect for each skin.
 

References:

[1] E. Proksch, J.M. Brandner, J.M. Jensen, "The skin: an indispensable barrier" a Dermatology, 17 (12): pp:1063–1072, 2008
[2] K.C. Madison, “Barrier function of the skin: “la raison d’etre of the epidermis””, Journal of Investigative Dermatology, 121 (2), pp: 231–241, 2003
[3] P. F. Millington,R. Wilkinson, “Skin”,  Cambridge University Press, pp:1-18, 1983
[4] S.F. Gilbert, "The Epidermis and the Origin of Cutaneous Structures", Developmental biology, 2000
[5] K.M. Halprin , "Epidermal "turnover time"--a re-examination". The British Journal of Dermatology, 86, pp: 14–9, 1972
[6] L. Bauman, “Cosmetic Dermatology – Principles and Pactice”, second edition, ISBN: 978-0-07-164128-9
[7]  L. C. Becker, W. F. Bergfeld, D. V. Belsito, C. D. Klaassen, J. G. Marks, R. C. Shank, T. J. Slaga, P. W. Snyder, F. Alan Andersen, “Final report of the safety assessment of allantoin and its related complexes,” Int. J. Toxicol., vol. 29, no. 3 Suppl, p. 84S–97S, May 2010.
[8] R. I. Peirano, T. Hamann, H.-J. Düsing, M. Akhiani, U. Koop, T. Schmidt-Rose, and H. Wenck, “Topically applied L-carnitine effectively reduces sebum secretion in human skin,” J. Cosmet. Dermatol., vol. 11, no. 1, pp. 30–36, Mar. 2012.
[9] A. Knott, U. Koop, H. Mielke, K. Reuschlein, N. Peters, G.-M. Muhr, H. Lenz, U. Wensorra, S. Jaspers, L. Kolbe, T. Raschke, F. Stäb, H. Wenck, and S. Gallinat, “A novel treatment option for photoaged skin,” J. Cosmet. Dermatol., vol. 7, no. 1, pp. 15–22, Mar. 2008.
[10] A. Rawlings , A. Davies , M. Carlomusto , S. Pillai, K. Zhang , R. Kosturko , “Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function”, Arch Dermatol Res,288, pp:383-90, 1996
[11] J. Linder, “The role of oils in topical treatment of Acne”, Cosmetic Dermatology, 21, pp:211-214, 2008
[12]  S. Quinta, P.C. Pinto, and L.M. Rodrigues, “Short-Term Impact of Low Concentration Salicylic Acid on the Cleansing Care of Normal Healthy Skin,” Journal of Applied Cosmetology, vol. 19, pp.37-50, April 2001.
[13]  L.L. Levy and J.L. Emer, “Emotional benefit of cosmetic camouflage in the treatment of facial skin conditions: personal experience and review,” Clin Cosmet Investig Dermatol., vol. 5, pp. 173-182, 2012.