Additionally, many studies that have investigated the response of photoaging attributes to products have been limited to lighter skin types as defined by Fitzpatrick types I, II, or III. This holds true for previous studies conducted with the polyhydroxy acid (PHA), gluconolactone.  Gluconolactone is the lactone form of gluconic acid that is found naturally occurring in the skin¹.  Studies with gluconolactone have demonstrated efficacy in reducing the signs of photoaging, as well as demonstrating compatibility with sensitive skin as defined by self-assessment² and by atopic and rosacea skin conditions³.  Gluconolactone has also been shown to provide a conditioning effect to skin barrier function as evidenced by reduced damage from a surfactant challenge⁴.  These studies utilized lighter skin types in their assessments, and a direct comparison of the response to some of these parameters by darker skin types is lacking.

The present study was conducted to gain some understanding of the inherent differences between African-American, Hispanic / Asian, and Caucasian skin as well as their response to a PHA containing regimen.

1. To assess if differences exist among measured skin surface parameters of three different ethnic groups (i.e. African-American, Hispanic / Asian, and Caucasian); and
2. To determine the response of these ethnic groups to a polyhydroxy acid containing regimen.

Specifically, these objectives were assessed through visual evaluation, self assessment, and / or instrumental measurements.

• Healthy females, 35-65 years of age with moderate photodamage
  • African-American, n=18
  • Caucasian, n=19
  • Hispanic / Asian, n=15 (9 Hispanic, 6 Asian)

• Conditioning Phase: Discontinue use of any topical products other than normal cleansers or non-medicated makeup, to the face and forearms for 2 days prior to study initiation 
• Participants must not have used topical AHAs or retinoids for 3 months prior to study initiation, or systemic retinoids for 12 months prior to study initiation
• Dermatologist visual assessments utilized a 5 point scale (none, mild, moderate, marked, severe)

Assessment of Inherent Differences

Assessments conducted at baseline visit using Courage-Khazaka instrumentation

• Face
  • Dermatologist visual assessment of photodamage including: roughness, uneven skin tone, hyperpigmentation, laxity, fine lines, deep wrinkles, overall photodamage severity
  • Dermatologist visual assessment of oiliness, objective irritation (erythema, peeling / dryness, inflammation, overall irritation), and inquiry of subjective irritation (burning / stinging and itching)
  • Sebumeter SM810 - measurement of amount of sebum (gu / cm²) assessed on midline of forehead
  • Skin pH Meter PH900 - measurement of skin pH assessed above left eyebrow
• Forearm
  • Dermatologist visual assessment of irritation including: erythema and peeling / dryness
  • Corneometer CM 825 - measurement of skin moisture (arbitrary units)
  • Tewameter TM 210 - measurement of barrier function by means of transepidermal water loss (TEWL) (g / hm²)
  • Chemical Challenge - a subgroup of subjects participated in an optional 6 hour 5% sodium lauryl sulfate (SLS) occlusive patch challenge with above measurements at 0, 24, and 48 hours post patch removal to determine resistance of skin to chemical insult (assessment of barrier integrity)

Assessment of Response to PHA Containing Regimen

• Study Duration: 12 weeks with visits at baseline, 2, 6, and 12 weeks
• Subject blinded, comparison to baseline
• Dermatologist visual assessment of photodamage as above
• Dermatologist visual assessment of oiliness, objective irritation, and inquiry of subjective irritation as above
• Self-assessment questionnaires

Test Materials

Twice daily application of cleanser and appropriate moisturizer to face

• Foaming Cleansing Gel: < 1% gluconolactone, pH 4.0
• Daytime Lotion, SPF 15: 4% gluconolactone, pH 3.7
• Nighttime Creme: 8% gluconolactone, pH 3.7

• Uneven skin tone and hyperpigmentation are more severe in darker skin
• Fine Lines, wrinkles, laxity and overall photodamage are more severe in lighter skin

• Erythema on the face was significantly higher in the Caucasian group compared to the other ethnicities
• There were no significant differences in inflammation, overall irritation, or subjective irritation (burning / stinging, itching)

• Caucasian has an increase in water loss immediately after patch removal and recovers similarly compared to the other ethnicities after 24 hours

• Differences exist among the ethnicities in the following areas:
  • Uneven skin tone is more apparent in darker skin types, perhaps due to light reflectance, optical properties, and post inflammatory hyperpigmentation of darker skin tones
  • Textural aging parameters such as fine lines, wrinkles, and laxity are more apparent in lighter skin most likely as a direct result of increased sun damage due to decreased inherent melanin protection
  • Chemical (SLS) Challenge data may indicate that Caucasian skin is initially more sensitive to chemical insult
• When using objective instrumentation, no differences were observed between the ethnicities for sebum production, or pH measured on the face, or moisture content (corneometry), or barrier function (TEWL) measured on the arm.
• No differences were seen upon visual assessment on the face for inflammation, overall irritation, or subjective irritation (burning / stinging, itching), or on the arm for objective irritation.

Response to PHA Containing Regimen

• All three ethnicities exhibited significant improvements in photoaging parameters after 12 weeks of use with the gluconolactone containing regimen.
• The PHA containing regimen was well tolerated by all three populations as evidenced by low objective irritation and no subjective irritation after 12 weeks of use.This is further supported by subject self assessment.
• African-American and Hispanic / Asian groups saw greater improvements in dermatologist assessment and self assessment for most parameters.
  • The lower severity of the parameters at baseline for these groups may provide a greater chance for improvement, especially in the textural aging parameters such as fine lines.
  • Alternatively, for more surface changes such as uneven skin tone and hyperpigmentation, a more severe condition may lend itself to showing greater improvements. 

1. Devlin TM, editor. Textbook of Biochemistry with Clinical Correlations. New York: Wiley-Liss, third edition; chapter 8.
2. Green B, Tseng C, Wildnauer R, Herndon J, Rizer R: Safety and Efficacy of a Gluconolactone (Poly Hydroxyacid) Containing Regimen on Sensitive Skin and Photodamage Following Controlled Consumer Use. Amer Acad of Derm Poster Exhibit: New Orleans, March, 1999.
3. Bergfeld WF, Remzi BK, Green B, Patel P, Ravas R: An Evaluation of the Gluconolactone Sensitive Skin Care Products. Amer Acad of Derm Poster Exhibit: Orlando, February, 1998.
4. Berardesca E, Distante F, Vignoli GP, Oresajo C, Green B: Alpha hydroxyacids modulate stratum corneum barrier function. British J Dermatol 1997;137:934-938.