Formulation of Bar Soap Containing Neem and Sulfur as Active Ingredients and Antibacterial Testing Against Propionibacterium acnes

Propionibacterium acnes is one of the main bacterial contributors to acne vulgaris, a prevalent dermatological condition. The prolonged use of topical antibiotics often leads to bacterial resistance, highlighting the need for safe and effective natural alternatives. Neem and sulfur are known for their antibacterial, anti-inflammatory, and keratolytic properties, but studies on their combined application in herbal soap formulations remain limited. This study aimed to formulate an antibacterial herbal bar soap combining neem extract and sulfur and to evaluate its physicochemical characteristics and antibacterial activity against P. acnes. The soap was prepared through saponification of coconut, palm, and olive oils (25%:35%:40%) producing four formulations: base soap (H1), neem soap (H2), sulfur soap (H3), and combined neem–sulfur soap (H4). Each formulation was assessed for organoleptic properties, pH, moisture content, free alkali and antibacterial activity against P. acnes with a commercial sulfur soap as positive control.All formulations met the reference standard of solid soap with pH 8.67–9.22,  moisture content 7.76–8.46 %, and free alkali <0.1%. The H4 formula showed the highest antibacterial activity with a 9.00 mm inhibition zone, surpassing the positive control (8.4 mm). The combination of neem extract and sulfur can be effectively formulated into a stable herbal antibacterial soap with significant inhibitory activity against P. acnes. This product shows promising potential as a natural therapeutic for acne-prone skin.