Most adults take 25–50 mg of diphenhydramine every 4–6 hours for itching, hives, or sneezing, staying within the label’s daily limit.

Too much diphenhydramine begins when you exceed the label’s 24-hour limit, then can escalate into confusion, seizures, and dangerous heart effects.

Too much diphenhydramine can trigger agitation, heart rhythm changes, seizures, or collapse in dogs, with risk rising fast as dose climbs.

For many adults, a common label dose is 25–50 mg every 4–6 hours, with a 24-hour cap of 300 mg unless a clinician sets a different plan.

Most dogs are dosed at 1–2 mg per pound per dose, given every 8–12 hours, using plain diphenhydramine only.

Most Tylenol PM caplets contain 25 mg diphenhydramine HCl per caplet, paired with 500 mg acetaminophen.

Typical adult diphenhydramine is 25–50 mg every 4–6 hours, with label limits and a high chance of drowsiness.

Most dogs start at 1 mg of diphenhydramine per pound per dose, given every 8–12 hours, unless your veterinarian sets a different plan.

A common diphenhydramine dose for dogs is 1 mg per lb (2–4 mg/kg), given every 8–12 hours, using plain diphenhydramine only.

For many dogs, diphenhydramine is dosed at 1 mg per pound (2–4 mg/kg) every 8–12 hours, after a vet says it fits your dog.