Which condition is defined as pain persisting for at least one month after rash healing?

Postherpetic neuralgia is defined as pain that continues for at least one month after the rash associated with herpes zoster (shingles) has healed. This condition occurs due to nerve damage from the varicella-zoster virus, leading to ongoing pain even after the visible symptoms have resolved. Individuals with postherpetic neuralgia often experience sharp, burning, or throbbing pain in the area where the rash occurred, which can significantly impact their quality of life.

In contrast, acute herpes zoster refers to the active phase of the infection when the rash and pain are present, while herpes simplex refers to a different virus that causes oral or genital herpes. Chronic pain syndrome involves long-term pain that can arise from various conditions but does not specifically pertain to the aftermath of herpes zoster. Thus, postherpetic neuralgia is uniquely characterized by its timing in relation to the healing of the herpes zoster rash, making it the correct answer.