A typical diphenhydramine starting dose for many dogs is about 1 mg per pound, so a 15-lb dog often lands near 15 mg per dose.

A typical single dose for a 12-pound dog lands around 11–22 mg of diphenhydramine, which often means a 12.5 mg half-tablet or a 10 mg chew.

An 8-year-old can usually take 12.5–25 mg of diphenhydramine per dose, based on weight and the package label, spaced 4–6 hours apart.

A common canine dose is 1 mg diphenhydramine per lb, so an 8-lb dog often takes 8 mg per dose, after a veterinarian says it fits your dog.

No, a toddler this young shouldn’t get diphenhydramine unless a clinician has told you to use it and given a weight-based dose.

For most kids this age, the safest amount depends on weight, the product’s strength, and a clinician’s direction.

Many vets dose plain diphenhydramine at 1 mg per pound, so a 70-lb dog may be given 70 mg per dose with veterinarian approval.

A common vet dosing rule for diphenhydramine is 1 mg per pound, so a 75-lb dog lands near 75 mg per dose, based on the exact product.

For a 7-year-old, diphenhydramine dosing is weight-based, so the right amount comes from the Drug Facts label using your child’s current weight.

For most 6-month-olds, the right amount is none unless a clinician gives a weight-based dose for a clear allergic reason.