Chemical Peeling

By Peter Roberts / 13 Feb 2017

Biochemist and clinical trial co-ordinator Peter Roberts explains how different chemical peel ingredients can effectively treat common facial skin concerns

Chemical peels have made somewhat of a comeback in the past few years. There used to be more concern amongst practitioners about the effects of harsh ingredients in the peels, leading many to err on the side of caution. Around the same time, a variety of lasers started to come on to the market and peels were seen as less favourable.

However, more recently, rather than being predominantly utilised for their exfoliating properties and influence on collagen matrix turnover, peels are being used to achieve significant results in common skin concerns.

There are many chemical agents available for skin peeling due to the advent of new ‘carrier’ systems,1,2,3,4,5 which vary in impact from exfoliators to deep skin re-modellers, through to treatments for acne, rosacea, lines and wrinkles, pigmentation and stretch marks. Used properly, I believe they can have substantial effects comparable to lasers and radiofrequency, and are far less likely to cause post-inflammatory hyperpigmentation (PIH).

In this article, I shall discuss the different types of peeling agents and the results that can be achieved.

Treating the skin with peeling agents

The newly developed carrier solutions take the acids and associated treatment ingredients (protected from degradation by the acid by the carrier solution) across the stratum corneum and deep into the skin before being released to target skin concerns. I recommend all peels are used in conjunction with creams – pre, post and in between peel treatments – which contain the same ingredients as those held in the peels. The peels will therefore boost activity of the creams.1,2,3,4,5

Below are some case study examples of multiple skin conditions that patients may present with and the appropriate peel treatments:

Case study 1: Patient A

  • Sun damage
  • Dark and puffy under eye
  • Reddening prone to rosacea
  • Spots and acne

Patient A has sun damage on the forehead, is prone to reddening and has some intermittent or permanent redness/vascularity in the central portion of the face. She also has recurrent outbreaks of spots around the chin and has dark and puffy areas under the eye – a delicate area of skin that needs a different approach. I would use specific solutions best suited to each of the above indications, rather than a ‘cocktail’ peel or glycolic acid. 

Glycolic acid is a general-purpose acid, it’s not lipophilic, and I believe other acids have better properties for specific skin issues. One might argue, if a patient had various skin issues in different areas of the face, that a ‘cocktail’ peel, i.e. a peel with multiple acid or peeling ingredients, may be ideal; but each acid in the cocktail will be applied to all areas of the face and some may have a negative effect on some of the skin issues mentioned, while being positive in others. The ‘cocktail’ combination could cause increased pigmentation on the forehead as well as exacerbate the central area and increase erythema and redness.

The diagram above represents a preferred choice of peels for Patient A. Please note that this is for a patient whereby we have assessed them for risk issues, such as skin ethnicities, dehydration and trans epidermal water loss (TEWL) issues, and found them to be low risk.

Mandelic acid is better for erythema control, salicylic better for oil reduction, Jessner’s (resorcinol, lactic and salicylic acid), is better for sun damage. Glycolic would not be my choice for any of these.9,10

Case study 2: Patient B (Fitzpatrick 2)

  • Wrinkles
  • Dark and puffy under eyes
  • Poor skin tone and sagging jaw line
  • Sallow skin and open pores

These indications are commonly presented and would all respond to a variety of different individual solutions. My preferred choice would be to use pyruvic acid, which is an alpha keto acid, on all facial areas, whereby the pyruvic acid is applied for one to three minutes, and depending on skin type and discomfort scores, I would consider a second layer for a further two minutes and then neutralise.

Around the eye I would suggest a lactic acid (tyrosinase inhibitor) and a resorcinol (preferential substrate for tyrosinase)-based multi layered gel. The number of layers applied would depend on skin sensitivity and PIH risk. Each layer would be applied for one to two minutes before the next one, and the last layer would be applied for up to five minutes, before the gel is wiped away and the area neutralised.

Both of these substances are tyrosinase-influencing and support a reduction in pigmentation manufacture.1,2 It is important to maintain levels of resorcinol containing creams going forward to continue to divert the tyrosinase away from melanin manufacture.

Patient B (Fitzpatrick IV-VI/skin problems)

Although you may see many patients with the exact same skin problems, it is not possible to treat everyone with the same solution. The patient’s skin sensitivity, Fitzpatrick skin type, ethnicity, and the severity of photo damage and wrinkles, should all be taken into consideration. The choice of agent will also vary depending on whether the patient has good skin moisture levels; for example, a high rate of TEWL coupled with low hydration may indicate poor lipid density, and this may lead to a higher sensitivity to the remodelling agent and increase risk of adverse events such as erythema and PIH. In this situation, I may revert to using a sequence of mandelic acid peels. The results may take longer to achieve but I would be mitigating for increased PIH risks.

Skin considerations

As mentioned, certain aspects should be taken into consideration before using any chemical peel.

Skin ethnicity

Patients with a mixed race background, who, for example, have a Celtic mother and an Arab father, where the patient may be a Fitzpatrick type 1, 2, 3 or 4, are traditionally assessed and treated as the darker parent would have been regardless of their Fitzpatrick type. This is because of concern about the level of inflammation the peel may cause and the risk of post treatment pigmentation increase. However, there is good data to suggest this may not be the most appropriate course of action. Fabil Fanous defined that facial features were more important than skin colour in determining PIH risk in mixed race patients. In simple terms, PIH risk is based on which parent the patient looked most like, irrespective of skin colour.7

For example, Celtic skin has high erythema sensitivity whereas Arab skin has a high PIH risk. The offspring and patient with this mixed ethnic background may have the same Fitzpatrick skin type as a southern European; but the patient would be treated differently and the choice would be based on facial features not just Fitzpatrick type. If their features looked like the Celtic parent, then their PIH risk would be lower. Ultimately, one size does not fit all. You need to ensure you do not cause long-term damage when treating the various skin types with peels, as you would with lasers.

Fitzpatrick skin type

The Fitzpatrick classification categorises skin type according to its reactivity to the sun without UV protection rather than the degree of photodamage. This classification helps identify patients who have a propensity for photodamage. This relates to their likely risk level and response when exposed to skin challenging procedures.11

For facial chemical peels, this classification can also be used to define the risk of pigmentary changes (e.g. dyschromia, post inflammatory hyperpigmentation, permanent hypopigmentation) and erythema when using resurfacing procedures. 


Figure 1: Fitzpatrick skin type classification

Glogau scale

The Glogau scale of photoageing consists of four age-range levels where each level is defined by describing how a typical person’s skin would appear in that age range and what visible symptoms they would typically manifest. Depending on the level of ageing, the depth and degree of treatment to the skin may need to be modified. More challenging skin concerns would traditionally need more of the same agent and also possibly for a longer exposure time; this would result in more trauma. An alternative approach is to expose the patient’s skin to either a lower level of treatment and/or a shorter exposure time but to spread out the treatments over five to eight sessions instead of the usual four. So it may be necessary to offer a different number of treatments, where the exposure time can be modified and the results will become prominent over a longer time period. 

Figure 2: The Glogau scale


Important considerations

  • If patients present with a poor skin condition, such as low hydration, TEWL, pigmentation issues and damaged blood vessels, then consider no peel, but use creams for boosting skin structure, repair processes, priming and preparation, regardless of skin type. Then, an appropriate sequence of peels may be considered, interspersed with creams and serums to boost their response but also to limit complication development, such as pigmentation increase.
  • Peels need water to move through the skin, therefore, skin with poor hydration is more likely to react to the acid component of the peel (hydrogen ions) and experience localised damage to the surface, is more irritating and more likely to lead to complications. This is because poor hydration causes less mobility for the hydrogen ions.13
  • The periorbital skin is much thinner than the rest of the face; hence this needs to be taken into consideration. The type of agent used can be similar, but the strength and surface activity needs to be lower. Phenols and high strength TCAs or pyruvic acid would not be appropriate. In my opinion, it is better to use lighter concentrations and add more layers. The number of layers used would vary depending on the patient’s skin type and sensitivity.
Figure 3: This graph combines the Fitzpatrick skin types with the Glogau scale 


Length of peel time

Due to the ability to transport remodelling agents into the skin using specialised patented carrier technology,1,2,3,4 this can reduce surface trauma normally seen with traditional peel solutions by up to 50%. Exposure time is set prior to application and the peel is neutralised or removed regardless of visible erythema or frosting. However, the visible symptoms of the peel and also patient response in terms of pain are still taken heed of, if trauma becomes apparent.

Exposure for mandelic is traditionally ten minutes, for pyruvic it is one to three and then if considered appropriate a second layer for up to a further two minutes, depending on layers and patient response, and for trichloroacetic acid (TCA) it is one to three minutes, before being neutralised. All other peels have varying exposure times.

Ideally, practitioners should use a neutraliser that can not only neutralise any surface acid, but also neutralise acid released in the skin. I use alkaline amino acids as a neutraliser as they can be attached to the same carrier molecules as used with the acids; in other words, wherever the carrier has taken the acid in the skin, the neutraliser can follow and neutralise both on and in the skin. Something like sodium bicarbonate is too big a molecule to carry into the skin and hence only neutralises on the surface.12

Mandelic usage has become more varied from a traditional ten-minute exposure and then neutralised, to also include now a partially extended or fully extended peel like a Jessner’s, whereby the solutions are left active in the skin and only any remaining unabsorbed solution is removed at ten minutes. The mandelate attached to the carrier is allowed to be released in the skin and convert to mandelic acid and is still active post the patient leaving the clinic, thereby extending the peels activity and boosting the results.1,2,3,4 With Jessner’s, the peel is not neutralised and only the salicylate white powder is removed that forms on the surface; as the salicylic acid deactivates and converts to this analgesic powder leaving the lactic acid and resorcinol components active to continue to target the tyrosinase enzyme to help reduce excess pigmentation.

The value of bespoke treatment protocols

When you have a range of different peels rather than one type of peel solution, such as glycolic, you have the opportunity to change the focus of the treatment to target other issues during a course of treatment, should the patient’s initial skin condition be resolved during the course of treatment, allowing you to focus on other skin issues. Bespoke peels allow the practitioner to switch and change peel choice during a course of treatment, depending on the patient’s skin journey and what changes take place during the treatment programme.

The correct patient assessment, prescription for the right areas and using the right exposure time leads to optimum outcomes for all patients.

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