Hydrogen ion in pH

Why is hydrogen ion concentration checked in liquid orals and ointment creams?

The negative log of Hydrogen ion concentration is pH. As you must be aware that the stability of active ingredients in oral liquid formulations, creams, and ointments largely depends on the pH of that formulation. Therefore, it is very important to maintain the pH of such formulations throughout their shelf life. Hence during the conduct of stability studies and also at the time of the release of freshly manufactured batches of such formulations pH is very important. It must be within the established specifications.

Generally, different types of buffers are used in the formulations to ensure that pH will not change significantly throughout the shelf life of such products.