Hi.
Noted the history about your 20 year old son having headache on getting up and now his lower body is cold, works at airport, take too much fast foods and plenty of water orally.
The commonest cause of morning headache are one of the following:
Hypertension causing headache is more once the blood pressure rises on getting up.
Additional
stress and
anxiety and as the age is 20 this is possible although he may not tell everything to the parents and thus gets entangled into more problems.
Neck muscle spasm.
Tension
headaches.
I would advise him the following:
Stop fast-food as these contain many preservative or taste enhancers that can be cause of allergic headache.
Regular check up at your Doctor for clinical evaluation, examination and get necessary investigations like
CT scan of brain and so on.
Once a proper diagnosis has been made then a specific treatment can be started and continued till he get results.
Hope I have answered your query. Let me know if I can assist you further.
Regards,
Dr. T. Chandrakant, General Surgeon