<p>Stringent humidity control is required in the pharmaceutical industry to maintain product stability and prevent adverse impact on drug quality. Exposure to extreme humidity conditions can cause microbial contamination and loss of therapeutic properties of drug products. Various regulations have been established by organizations such as the World Health Organization (WHO), the Food and Drug Administration (FDA), and the US Pharmacopeia (USP) to ensure humidity control stays within defined ranges. Humidity sensing is crucial for maintaining optimal conditions in healthcare facilities, production lines, and sterile storage. Conventional humidity sensing is facing limitations in sensitivity, stability, and measurement range. The hygroscopic materials improve the humidity sensing performance with increased surface area, providing more active sites for water molecule adsorption. This paper explores the synthesis of a novel metal oxide sensing material using hexamethylenetetramine (HMT) and examines the hygroscopicity of the synthesized sensing material. In the study, tin dioxide (SnO₂) and zinc oxide (ZnO) were synthesized via the low-temperature hydrothermal method with and without additive-enhanced technique. The sensing materials were evaluated for its potential in humidity sensing improvement by conducting a hygroscopicity test and the linear equation was analyzed to compare the slope of mass uptake ratio under incremental and decremental relative humidity (RH). The result demonstrated humidity sensing enhancement can be achieved with the presence of HMT due to the porous structure and hydrophilic nature. From the hygroscopicity test result, the slope of ZnO-HMT was ~ 2x higher compared to ZnO, while SnO₂-HMT was ~ 3x higher compared to the SnO₂ counterpart. This result suggests that the additive-enhanced sensing material has the potential for improving humidity sensing in pharmaceutical applications, offering a promising solution for humidity optimization across the industry.</p>