Why might bacteria be present on hands after washing with soap and water?

The assertion that soap does not remove all bacteria is a valid explanation for why bacteria may still be present on hands after washing. While soap is effective in breaking down oils and lifting dirt, grime, and microbes off the skin, it does not guarantee the complete removal of all bacteria. Factors such as the thoroughness of washing, the duration of the wash, and the effectiveness of the rinsing process can influence how well bacteria are eliminated. Some bacteria may adhere more tenaciously to the skin or may be sheltered in areas that are difficult to clean thoroughly, such as under fingernails or between fingers.

Washing with soap and water is an important practice in hygiene, reducing the number of pathogens significantly, but it may not achieve total sterility. Total sterility is an unrealistic expectation for handwashing in everyday life. Thus, while soap is a critical component in reducing bacteria, it does not completely eradicate them from the hands.