My Male Friend, 58 Years Old, Has Had A Very

My male friend, 58 years old, has had a very bad headache for 3-4 days. It is behind his right eye. It is continuous and sharp - shooting straight back and down the back of his ear. He has no other symptoms, nor fever. History of Parkinson's. Stage 2\3. He also drinks beer pretty much daily. What could be causing this headache?