I had a flu shot yesterday. 4 hours later struck with extreme dizziness and sweating. is that normal?

Maybe: Dizziness and sweating are very vague symptoms with many causes. You should check with your doctor. Flu shots have many proteins (antigens) so that your body will produce antibodies and protect you from the flu. This response includes cytokines, a chemical messenger that can cause symptoms in sensitive people. However, they still should get the vaccine because influenza is much worse.