Give 1mg of Benadryl per pound such that if your dog weighs 30 pounds, you should give it 30 mg of Benadryl. Talk your veterinarian - while antihistamines are generally safe, there are the potential for side effects particularly if your dog has chronic organ failure (renal failure, liver failure, congestive heart failure, etc.).
1 Encephalitis is inflammation of the brain.  Meningitis is inflammation of the membranes (called meninges) that surround the brain and spinal cord.
Encephalitis is a condition where the brain becomes inflamed due to a virus or other types of infections. One kind of virus that can cause encephalitis is Herpes simplex type 1 (HSV-1).Although Herpes simplex type 1 most often causes mild symptoms like cold sores and fever blisters, it can occasionally travel to the brain and cause encephalitis.ne kind of virus that can cause encephalitis is Herpes simplex type 1 (HSV-1). Although Herpes simplex type 1 most often causes mild symptoms like cold sores and fever blisters, it can occasionally travel to the brain and cause encephalitis.