Benadryl (diphenhydramine) typically takes about 15 to 30 minutes to start working after oral intake. It reaches its peak effects within 1 to 2 hours. The relief from allergy symptoms or other indications usually lasts for about 4 to 6 hours. Injectable forms of Benadryl work faster, and topical forms may take much longer to have an effect. The sedative effects also appear within this time frame. This timeline can vary based on factors like the form of the medication (liquid may work faster than tablets), individual metabolism, age, weight, and other health conditions. It is advised to follow dosing instructions carefully and avoid taking an extra dose too soon even if symptoms persist. In summary:
- Start of effect: 15 to 30 minutes
- Peak effect: 1 to 2 hours
- Duration: 4 to 6 hours
These findings are consistent across multiple reliable sources.
