- Journal List
- Indian J Dermatol
- v.59(5); Sep-Oct 2014
- PMC4171909
As a library, NLM provides access to scientific literature. Inclusion in an NLM database does not imply endorsem*nt of, or agreement with, the contents by NLM or the National Institutes of Health.
Learn more: PMC Disclaimer | PMC Copyright Notice
Indian J Dermatol. 2014 Sep-Oct; 59(5): 442–444.
PMCID: PMC4171909
PMID: 25284846
Jose Tarun, Jose Susan, Jacob Suria, Veronica John Susan, and Sebastian Criton
Author information Article notes Copyright and License information PMC Disclaimer
Abstract
Background:
Normal healthy skin has potential of hydrogen (pH) range of 5.4-5.9 and a normal bacterial flora. Use of soap with high pH causes an increase in skin pH, which in turn causes an increase in dehydrative effect, irritability and alteration in bacterial flora. The majority of soaps and shampoos available in the market do not disclose their pH.
Aims and Objectives:
The aim of this study was to assess the pH of different brands of bathing soaps and shampoos available in the market.
Materials and Methods:
The samples of soaps and shampoos were collected from shops in the locality. The samples of different brands are coded before the analysis of the pH. Solution of each sample was made and pH was measured using pH meter.
Results:
Majority of the soaps have a pH within the range of 9-10. Majority of the shampoos have a pH within the range of 6-7.
Conclusions:
The soaps and shampoos commonly used by the population at large have a pH outside the range of normal skin and hair pH values. Therefore, it is hoped that before recommending soap to patient especially those who have sensitive and acne prone skin, due consideration is given to the pH factor and also that manufacturers will give a thought to pH of soaps and shampoos manufactured by them, so that their products will be more skin and hair friendly.
Keywords: Acne vulgaris, propionibacterium, shampoo, skin potential of hydrogen, soap
What was known?
Many researches have been conducted on the measurement of potential of hydrogen (pH) of skin and effects of soaps on skin pH. However, there are not many studies on the pH of soaps and shampoos that are commonly available in the market and those used by the majority of the population.
Introduction
The surface of the skin is slightly acidic, giving rise to the concept of the acid mantle.[1] Studies have shown that potential of hydrogen (pH) of skin increases in proportion to the pH of cleanser used. Increase in pH causes an increase in dehydrative effect, irritability and propionibacterial count.[2,3,4] Changes in the pH are reported to play a role in the pathogenesis of some skin diseases. Therefore, the use of skin cleansing agents with a pH of about 5.5 may be of relevance in the prevention and treatment of those skin diseases.[5,6]
Unfortunately, pH is not mentioned in the labels of many products.
Objective
The objective of this study was to assess the pH of different brands of bathing soaps and shampoos available in the market.
Materials and Methods
Sample collection
Samples of branded soaps and shampoos were collected from shops in the locality. They included bathing soaps, Anti-acne soaps, ayurvedic soaps and those promoted for dermatological conditions. A sample of homemade soap was also collected. We also collected a sample of imported soap to compare with the same brand in the Indian market.
Determination of pH
Readings of pH were taken using ELICO L1613 pH meter after calibrating with the standard solution supplied by NICE Chemicals Pvt. Ltd., Kochi, Kerala (pH = 7). The samples were coded before the analysis of the pH. Procedure was divided so that one person was involved in measuring the sample, another in coding, then another in mixing and the last person in the measurement of pH, so that the person involved in measurement of pH does not know the identity of the sample being tested. The pH of distilled water used ranged from 6.24 to 6.88.
Procedure used for soap
Soap sample weighing 150 mg was mixed in 15 ml distilled water without producing much lather. It was kept undisturbed for 24 h for maximum dissolution of soap. Then the pH of each sample was measured.
Procedure used for shampoo
Sample of shampoo of 1.5 ml is taken in a glass beaker and water is added to the sample to make its volume to 15 ml. Mixing is done well without producing lather. The solution is kept undisturbed for 30 min. Then the pH of each sample was measured.
Results
Of the 64 samples of soaps tested, 53 had a pH within the range of 9.01 to 10. Only two samples were in the range of skin pH [Table 1].
Table 1
Total number of soap samples in the various pH range
Open in a separate window
Five of the 64 samples analyzed were promoted as anti-acne soaps. Of these, three were within the range of 9.01 to 10 and two in the range of 10.01 to 11 [Table 2].
Table 2
Various types of soap samples in the various pH range
Open in a separate window
Nine of the 64 samples, which were marked as ayurvedic soaps had a pH in the range of 9.01 to 10 [Table 2].
Three of the 64 samples were promoted for dermatological purpose. Two out of three had a pH in the range of 9.01 to 10 [Table 2].
Homemade soap had a pH range in 9.01 to 10.00. The sample of imported soap had a pH in the range of 9.01 to 10, which is same as that of the same brand in Indian market. Different varieties of the same brand were also tested. The difference in the pH between varieties of the same brand was within 0.35. The pH of various varieties of Brand coded A was within 9.62 ± 0.08, Brand B was within 7.445 ± 0.125, Brand C was within 9.79 ± 0.16 and Brand D was within 9.88 ± 0.10.
Of the 38 samples of shampoos tested, 24 had a pH within the range of 6.01 to 7. Seven of the 38 samples had pH in the range of 7.01 to 8, six in the range of 5.01 to 6 and only one in the range of 4.01 to 5 [Table 3].
Table 3
All the shampoo samples in the various pH range
Open in a separate window
Discussion
The results of our study revealed that only 3.125% of the soap samples tested had a pH corresponding to that of skin pH and another 3.125% had a neutral pH. Upon reviewing these products, it was found that these products have mentioned their pH and the findings of our study were consistent in the pH claimed by them. The rest of the products with alkaline pH have not mentioned anything regarding their product's pH value. Even those products, which were promoted as anti-acne soaps had a pH above nine. Since studies have proved that propionibacterium is implicated as one of the factors of pathogenesis of acne and that their count increases on the use of alkaline soap, it is very important that at least these products have a pH consistent with that of skin pH. Even, the products prescribed for dermatological purposes had an alkaline pH. Ayurvedic soaps, which claimed to be better than other soaps were not skin friendly in the aspect of their pH.
In a study done by Tyebkhan G, in which pH paper was used for measuring the pH of soaps/cleansers, it was found that the soaps commonly used by the population at large have a pH ranging between 7 and 9. Also, only 3 samples of those tested had a pH in keeping with the normal skin.[7] But in our study, we have found that majority of the samples had a pH ranging between 9.01 and 11. Also, only 2 samples of those tested had a pH corresponding to that of the skin pH. The difference may be due to greater accuracy of the pH meter used in our study when compared to the pH paper.
Acid balanced shampoos are recommended generally by experts and in our study we found that 81.58% of shampoos had an acidic pH. When compared to soaps, shampoos are better in respect to their pH.
The soaps and shampoos commonly used by the population at large have a pH outside the range of normal skin and hair pH values. Therefore, it is hoped that before recommending soap to patient especially those who have sensitive and acne prone skin, due consideration is given to the pH factor and also that manufacturers will give a thought to pH of soaps and shampoos manufactured by them, so that their products will be more skin and hair friendly.
What is new?
This is the first study in India, which used a pH meter to measure the pH of commonly used soaps and shampoos instead of pH paper. Hence, it is more accurate.
Footnotes
Source of Support: Amala Institute of Medical Sciences, Thrissur, Kerala
Conflict of Interest: Nil.
References
1. Braun-Falco O, Korting HC. Normal pH value of human skin. Hautarzt. 1986;37:126–9. [PubMed] [Google Scholar]
2. Gehring W, Gehsen M, Zimmerman V, Gloor M. Effects of pH changes in a specific detergent multicomponent emulsion on the water content of stratum corneum. J Soc Cosmet Chem. 1991;42:327–33. [Google Scholar]
3. Baranda L, González-Amaro R, Torres-Alvarez B, Alvarez C, Ramírez V. Correlation between pH and irritant effect of cleansers marketed for dry skin. Int J Dermatol. 2002;41:494–9. [PubMed] [Google Scholar]
4. Korting HC, Kober M, Mueller M, Braun-Falco O. Influence of repeated washings with soap and synthetic detergents on pH and resident flora of the skin of forehead and forearm. Results of a cross-over trial in health probationers. Acta Derm Venereol. 1987;67:41–7. [PubMed] [Google Scholar]
5. Schmid-Wendtner MH, Korting HC. The pH of the skin surface and its impact on the barrier function. Skin Pharmacol Physiol. 2006;19:296–302. [PubMed] [Google Scholar]
6. Mukhopadhyay P. Cleansers and their role in various dermatological disorders. Indian J Dermatol. 2011;56:2–6. [PMC free article] [PubMed] [Google Scholar]
7. Tyebkhan G. A study on the pH of commonly used soaps/cleansers available in the Indian market. Indian J Dermatol Venereol Leprol. 2001;67:290–1. [PubMed] [Google Scholar]
Articles from Indian Journal of Dermatology are provided here courtesy of Wolters Kluwer -- Medknow Publications
