Comparative quality, efficacy, heavy metal content and safety of selected african black soaps for skincare

Background: There is an upsurge in the utilization of African black soaps. Hence, there is a need for evaluation of their quality and safety.

Objectives: The aim of this study was to evaluate the quality, efficacy, heavy metal content and safety of selected African black soaps. 

Methods: The physicochemical properties of twelve black soaps were evaluated. Microbial load was analyzed and anti-microbial activity was evaluated. Heavy metal content was analyzed using atomic absorption spectrophotometer, environmental toxicity was analyzed using Allium cepa test, and skin irritation tests were also evaluated.

Results: The black soaps showed fair physicochemical properties. The soaps showed the absence of microbial colonies. All the soap samples showed antimicrobial efficacy against all the organisms tested except sample UPS2 which exhibited no anti-microbial activity against Pseudomonas aeruginosa. The study revealed the presence of 3+ heavy metals (Pb, Cd, As, Hg and Cr ) which were within acceptable limits; none of the soaps posed a carcinogenic or non-carcinogenic risk. The Allium cepa test showed that African black soaps tested retarded onion root growth. The skin irritation test (wash-off test) showed that the post-wash pH was between 4.95- 5.76. There was an increase in the post-wash trans-epidermal water loss in 87.5 % of the subjects and decrease in postwash sebum content in 62.5 % of the subjects.

Conclusion: This study has shown that there is a great prospect in the utilization of black soaps; however, there is 
a need for regulation of raw materials, standardization of manufacturing processes and proper disposal of black soaps in order to safeguard public health.