I already gave him 50mg should I go to 75mg? He has an appt tomorrow with his vet for his terrible hot spots but I can tell he is so itching and in a lot of discomfort. How long does it take for the Benadryl to kick in? Please help! He is crying/whining and its breaking my heart 
Also, he is a large male dog
lap* sorry
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Typical dosage for Benadryl is between .5 mgs and 2 mgs per pound, every 8-12 hours.
So you could go up to 75mg safely, yes, as long as he has no other health problems and is not taking any other CNS depressants.
Be sure you keep meticulous records of what you gave him and when, in case you vet wants to administer any meds tomorrow. He needs to know what is already in your dog’s system to do anything else safely!
I wouldn’t give him anymore benadryl.
Yea, my dog is the same way it IS heartbreaking to watch then scratch like crazy. My dog has seasonal allergies and she is excited for autumn to come
Have you looked into Cream of Tarter, an all natural antihistamine blocker I don’t really ever give my dog benadryl anymore as the cream of tarter seems to be stopping the histamines. I also bathe her with soothing aloe and oatmeal shampoo frequently.
The vet always give my dog prednisone, but I hate giving it to her because its taxing to her liver or kidneys..sorry I can’t remember exactly which organ.
I never take benadryl, but had to the other day cuz I was stung by an Asps Caterpillar…and with in 45min. it knocked me out.
Administer 200mg of Morphine. Works for humans too !!!!