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.
From Wikipedia, the free encyclopedia. Acute disseminated encephalomyelitis (ADEM) (or acute demyelinating encephalomyelitis) is a rare autoimmune disease marked by a sudden, widespread attack of inflammation in the brain and spinal cord.rom Wikipedia, the free encyclopedia. Acute disseminated encephalomyelitis (ADEM) (or acute demyelinating encephalomyelitis) is a rare autoimmune disease marked by a sudden, widespread attack of inflammation in the brain and spinal cord.