A comparative study of sebum secretion rates and skin types in individuals with and without acne

 

Ajay Govindrao Ovhal^1*, Jerajani H R², Dhurat R S³

 

Abstract              Background: Sebum is always listed as one of the important factors involved in the pathogenesis of acne.The activity of sebaceous gland has been evaluated by measuring the Sebum Excretion Rate (SER). The facial SER depends upon the topography of the face. Aim: To compare sebum secretion rates and skin types in individuals with and without acne. Material and Methods: In this prospective clinical study, a total of 100 individuals 60 patients (Study group) and 40 (Control group) were enrolled. Facial sebum secretions were measured using a Sebumeter from five different facial sites. Results: Despite of having oily skin type in more number of acne patients, there were no statistically significant differences of sebum secretion between the acne and control groups in any facial region. Contrary to finding in oily skin type, in the normal skin type, the patient group showed more sebum secretion than the control group in all facial regions. The non-inflammatory lesions were significantly more in oily skin than normal skin type, whereas mean inflammatory lesions were not significantly more in oily skin type. Conclusion: In patients with acne, sebummay be the one of the factors in pathogenesis of acne. Sebum secretion correlated with inflammatory and non-inflammatory lesions in T-zone but not in U-zone. Thus, other factors responsible for pathogenesis of acne, as a whole should also be considered

Key Word: Acne, sebum, oily skin, Sebumeter,Sebum Excretion Rate

 

INTRODUCTION

Over the last three decades, scientific understanding of the pathogenesis of acne vulgaris has increased considerably. In response to this growth in knowledge, the clinical focus of acne therapy has shifted from resolution of advanced lesions to inhibition of multiple processes underlying the earliest stages of the disease. Excessive oiliness or dryness affects cosmetic appearance of the skin. Hence, estimation of oiliness is important to decide on the correct regimen to achieve cosmesis. The activity of sebaceous gland has been evaluated by measuring the Sebum Excretion Rate (SER) on large surfaces.¹ The facial SER depends upon the topography of the face. It is said that T- zone (area including forehead, nose and chin) is greasier then U-zone (area involving both cheek).² However, in most studies the methods used for measuring SER were inconvenient and not standardized, and topographical difference of SER, of facial skin was not considered. The present study was conducted to compare sebum secretion rates and skin types in individuals with and without acne.

 

MATERIAL AND METHODS

In this prospective clinical study, a total of 100 individuals 60 patients (Study group) and 40 (Control group) were enrolled and studied over a period of 6 weeks. Control group involved the age matched normal healthy subjects. As it is difficult to find individual who never had experienced an acne lesion, we included controls, who never had more than 5 acne lesions, together at any point of time and no visible acne at the time of measurement.

Inclusion criteria

• Individuals between age group of 13 to 30 years
• Both sexes
• Fresh, untreated patients with acne vulgaris.

Exclusion criteria

• Patients who have received topical acne treatment within previous 2 weeks
• Patients who have received oral antibiotics or systemic or topical anti-inflammatory drugs within the previous 4 weeks, or oral isotretinoin within previous 6 months
• Pregnant, nursing mothers
• Females in reproductive age group not ready to use birth control.
• History of hypersensitivity to topical retinoids

Sebum was collected from each site on a plastic strip using a constant pressure for 30s (Fig.3). Participants were asked not to use any cosmetics and not to wash face within two hrs of measurement. Amounts of sebum secretion were recorded and mean facial sebum excretion (MFSE) was calculated. Measurement areas were classified as follows: high sebum secreting zone (T- zone; forehead, nose and chin) and low sebum secreting zone (U- zone; both cheeks).All procedures were performed by same investigator in a room at constant temperature (22-25⁰C). The patient facial skin types were determined using the sebum secretion guidelines supplied with the Sebumeter. However, because these guidelines list reference values for individual measurement sites only, they could not be used directly for determining the skin types of the T- Zone, the U- Zone or the whole face (MFSE). Thus, we obtained new sebum secretion reference values for these areas by calculating the mean value for each location (Table 1).

 

 

Table 1: Reference values for the evaluation of facial skin types by sebum secretion measured with the Sebumeter^® (µg cm^-2) (control group)

        MFSE = mean facial sebum excretion.

 

The reference values were calculated by the following equations using regional reference values for sebum secretion suggested by the manufacturers:

1. Whole face = [sum of reference values for the forehead, nose, chin and both cheeks]/5;

2. T-zone = [sum of reference values for the forehead, nose and chin]/3;

3. U-zone = [sum of reference values for both cheeks]/2.

Clinical Digital Photographs and Lesion Counting

Four clinical photographs were taken of the patients with acne: en face, forehead and right and left lateral profiles. All photographs were taken using a digital camera (DSC-F717; Sony, Tokyo, Japan). We divided the surface of the face into forehead, right cheek, left cheek, nose and chin areas. The boundaries of these areas were determined based on regional variations in sebum secretion. Acne lesions were classified as non-inflammatory (non-inflammatorycomedonal papules) or inflammatory lesions (including inflammatory papules, pustules, nodules and cysts). Forehead, nose and chin acne lesions were counted using magnifying glass in good illumination. This work was done by single dermatologist, to minimize individual error with respect to lesion classification. Global assessment was done 2 weekly by single dermatologist depending upon his impression of reduction in lesions. The scoring was done as excellent if improvement was >90%, good if between 75-90%, fair if 50-70% and poor if <50% or exacerbation.

Statistical Analysis

Comparisons between patients and controls with respect to amounts of sebum secreted and of acne lesion counts for oily and normal skin types were done using Student's t-test. The strength of the association between sebum secretion and acne lesion number was evaluated using Pearson's correlation coefficients. P<0.05 was considered to be statistically significant.

 

RESULTS

In the present study, 60 patients with acne (35 males, 25 females) and 39 controls (25 males, 15 females) were enrolled in the study. The mean age of the control and cases group was 20.03 years and 20.34 years respectively, which was statistically similar (P > 0.05). Mild acne (Grade I) was seen in 22.5%, moderate acne (Grade II) in 42.5% and moderately severe acne (Grade III) in 27.5%. Sebum secretion was elevated in the acne group.The MFSE ± SD of controls and patients with acne was 52.86 ±28.54 µg cm^-2 and 79.12 ± 40.68 µg cm^-2, respectively. Sebum excretion at T- zone in control group was: 65.29 ± 33.29 µg cm^-2 and U-zone: 40.41 ± 27.5 µg cm^-2. Whereas sebum excretion in patients with acne at T-zone was: 93.57 ± 45.6 µg cm^-2, and U-zone: 64.68 ± 46.33 µg cm^-2. Thus, sebum excretion in patient group at both T and U zones was statistically significantly higher than that in control group. Hence, there was statistically significant difference in sebum secretion between two groups in every facial zone (P<0.01).

 

Table 2: Classification of Facial Skin Type According to Mean Facial Sebum Excretion

 

 

Table 3: Classification of Skin Type According to the Sebum Secretion of T-Zone

 

Table 4: Classification of Skin Type According to the Sebum Secretion of U-Zone

Also, MFSE in males was 87.78 ± 45.83, which was significantly higher than that in females 79.12 ± 40.68 (P < 0.05). A normal skin type was found in most controls (68.42%), and oily skin type in most acne patients (58.33%). The oily skin type was higher in the T-zone in acne group than control group: 58.33% in the acne patient group and 18.42% in the control group. The U-zone had normal skin type as a most common type in acne (68.33%) as well as control group (71.05%). When sebum secretion was calculated on the oily skin types, there were no statistically significant differences of sebum secretion rate between the acne and control groups in any facial region. However, for the normal skin type, the patient group showed more sebum secretion than the control group in all facial regions. Statistical analysis was not done on the dry skin type because of none of the patients had this type of skin. By facial skin type, a statistically significant difference was found between the mean numbers of inflammatory lesions between oily and normal skin types in the patient group. Also, in terms of total acne lesions, statistically significant difference was found between oily and normal skin type (Table 5).

 

 

Table 5: Numbers of Acne Lesions According to Skin Type in patient group

The mean SER of T zone (93.57±45.60) was more than that in U zone (64.68±46.33) in patients with acne. The total number of non-inflammatory as well as inflammatory lesions was more in the U zone (41.63±21.94) than the T zone (30.71±16.33). The mean number of different types of acne lesions in different facial regions is shown in Table 6 for the patient group. The mean±SD number of total acne lesions (T+U zone), non-inflammatory and inflammatory acne lesions was 72.35±32.35, 49.02±26.63and 23.33±13.83, respectively.

A correlation analysis using logistic regression was performed to establish the relation between regional facial sebum secretion and number of acne lesions by type (Table 6). Significant relations were found between MFSE and mean inflammatory lesions of the whole face (γ = 0.3724, P < 0.01), MFSE and total lesions of whole face (γ = 0.3232, P < 0.01), inflammatory lesions of the T-zone (γ = 0.3930, P < 0.01), non inflammatory lesions of the T-zone (γ = 0.3582, P < 0.01) and total acne lesions of the T-zone (γ = 0.4579, P < 0.001). However, in U-zone the numbers of acne lesions, regardless of type, were not found to be significantly associated with sebum secretion (Table 6).

 

Table 6: Correlations between Facial Sebum Excretion and Acne Lesion Counts

MFSE = mean facial sebum excretion; γ = Pearson's correlation coefficient. *P< 0.05.

 

DISCUSSION

In this study, we categorized the patients into: dry, normal and oily skin types based on the reference values derived from the control group (Table 1). In addition, we measured sebum secretion at five locations on the face to consider regional variations in sebum secretion. The patients with acne had mostly oily skin type (58.33%) as compared to the controls, who mainly had normal skin type (68.42%). Further stratifying the skin type according to T and U zone, T-zone: 58.33% of acne patients had oily skin type as compared to 68.42% of controls with normal skin type and U zone: 68% acne patients had normal skin type as compared to 71.05% controls with normal skin type.

The study done by Youn et al,³ found normal skin in most of the acne patients (80%) and dry skin in most of the controls(61%). At T-zone 65% patients with acne and 80%controls, had normal skin. U- zone had mostly (76%) dry skin in patients and normal skin (80%) in controls. However, they did not have enough patients with oily skin type for analysis. Our findings are different from this study but correlate with the previous studies which state that acne patients have oily skin. Also our findings in T area are according to the expectation of oiliness of the T area as compared to those in U area. The non-inflammatory lesions were significantly more in oily skin type than normal skin type. Despite most of the acne patients having oily skin type, surprisingly, mean inflammatory lesions were not significantly more in this skin type. For inflammatory acne lesions there was no statistical difference between oily and normal skin type. Youn et al,³ found significantly higher number of inflammatory lesions in normal skin type as compared to the dry skin type. For non-inflammatory acne lesions there was no statistical difference between oily and normal skin type. Our findings were opposite to above mentioned study but may be explained by comedogenic property of sebum. Reported studies have blamed free fatty acids and squalene present in sebum, for inducing comedones.^4,5 While in case of inflammatory lesions, oiliness may be an associated finding as seen in present study where inflammatory lesions were not significantly higher in oily skin than normal skin type.

The absence of correlation between sebum secretion and lesion counts in some regions (U- zone) suggests that secreted facial sebum cannot be the sole factor inciting the development of acne lesions. The increased sebum secretion is considered a major component in the pathogenesis of acne, but increased sebum secretion simply increases the likelihood of developing acne lesions, and does not constitute a direct and unique cause of lesion development. The scalp secretes high levels of sebum, but comedogenesis is rarely observed even in patients with severe acne.⁶ The present study shows that, total and non-inflammatory comedones on the U zone, as well as inflammatory and total acne lesions in the U-zone, were not significantly associated with local sebum secretion. Also, their correlation coefficients did not show strong associations, which imply that other factors play an important role in the development of acne in these regions.

 

CONCLUSION

In conclusion, increased facial sebum secretion was found in acne patients as compared to the controls. In patients with acne, sebummay be the one of the factors in pathogenesis of acne. Sebum secretion correlated with inflammatory and non-inflammatory lesions in T zone but not in U zone. Thus other factors responsible for pathogenesis of acne, as a whole should also be considered.

 

 

 

 

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2. Park SG, Kim YD, Kim JJ, Kang SH. Two possible classifications of facial skin type by two parameters in Korean women: sebum excretion rate (SER) and skin surface relief (SSR). Skin Res Technol 1999; 5:189–94.
3. Youn SW, E‐S. Park ES, Lee DH, Huh CH, Park KC. Does facial sebum excretion really affect the development of acne? Br J Dermatol 2005; 153: 919-924.
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