Benadryl (diphenhydramine) typically starts working within 15 to 30 minutes after oral administration, reaching peak effects around 1 to 2 hours
. The primary effects usually last about 4 to 6 hours, although some sources note effects can extend up to 7 hours
. The half-life of Benadryl-the time it takes for half of the drug to be eliminated from the body-varies between approximately 2.4 to 9.4 hours depending on individual factors such as age, metabolism, and health
. This means it can take roughly 13 to 49 hours for the drug to be fully cleared from the system
. While the noticeable effects wear off within 4 to 6 hours, Benadryl can remain detectable in the body for up to 24 to 60 hours, depending on factors like dosage, age, and organ function
. Side effects such as drowsiness or dry mouth may linger beyond the main effect period, especially in children, seniors, or those with slower metabolism
. In summary:
- Onset: 15–30 minutes
- Peak effect: 1–2 hours
- Duration of main effects: 4–6 hours (up to 7 hours)
- Half-life: 2.4–9.4 hours
- Time to clear from body: 13–49 hours (up to 60 hours detectable)
These durations can vary based on individual physiology and dosage
