Hello, Thanks for writing to us with your health concern. Some persons may have an excessive emotional upset and autonomic response like fall in blood pressure, sweating, loss of consciouness etc. Another reason may be postural hypotension if a person has adopted upright posture suddenly from sitting or supine position. The last but not the least possibility is of hypoglycemia. In either case he should be evaluated by a local physician thoroughly and decide on definitive diagnosis. Looking forward to hearing from you. Take care.