Background Skin and soft tissue infections are frequent. Candidiasis and Aspergillosis are the most common cutaneous fungal infections. Yemeni alum (Aluminium Potassium Sulphate) is a natural mineral with antifungal and antibacterial properties. Objective This study aimed to confirm Yemeni alum's antifungal effectiveness against selected fungal strains and develop useful topical formulations. Methods Using different alum concentrations, we prepared twenty-three formulations, including four non-adjusted aqueous solutions, eight adjusted pH aqueous solutions, eight glycerite solutions, and three Oil/Water cream formulations. Then, we examined the antifungal activity against the suggested fungus. The animal skin irritation test evaluated the local skin sensitivity reactions that might happen upon using the formulations we prepared on the intact animal's skin. Additionally, this study also included six weeks of stability testing to estimate the expected shelf life (t90) of the selected formulations. Results Alum exerted antifungal effect against Candida albicans, Aspergillus niger, and Aspergillus flavus. The animal's skin was not irritated by any of the formulations examined. The 5% alum aqueous solution and the 10% alum Oil/Water cream exhibited promising results among all tested formulations. The approximate formulation's shelf-lives (t90) were 2 and 1.52 years with alum content (%) ranging between 105.75% to 106.02%, respectively. Conclusion Based on the results we found, 10% alum Oil/Water cream is a promising formulation for large-scale manufacture.