What is a small white pill with the number 223?

A small white pill marked with the number "223" is identified as Diphenhydramine hydrochloride 25 mg, an over-the-counter antihistamine. It is commonly used to relieve symptoms of Allergies, hay fever, and colds, such as runny nose, sneezing, and itching. Additionally, it is often used as a sleep aid due to its sedative properties. Always consult a healthcare professional before taking any medication.