The lethal dose of diphenhydramine, the active ingredient in Benadryl, can vary widely depending on the individual, including factors like age, weight, overall health, and specific medical conditions. While there isn't a universally accepted "lethal dose," significant toxicity can occur at doses much higher than the recommended therapeutic doses.
For adults, the typical therapeutic dose for allergic reactions is 25-50 mg every 4-6 hours as