The views expressed by me are for educational purposes only and do not establish a doctor patient relationship.
Thanks for your question.
Cold or wet feeling can be due to the nerve problem.
Nerves from the scalp carry the sensation to the brain.
If the nerve is transmitting abnormal sensation, then this will be perceived like this.
This is also known as sensory abnormality.
This can be seen with any nerve impingement at the cervical spine ( back of neck).
Stroke or TIA can also present like this.
Underlying medical conditions like diabetes, hypertension, thyroid problem, vitamin B12 deficiency are other causes.
This should be checked out by his GP.
If he develops any other symptoms like weakness, dizziness, slurred speech, then urgent evaluation is necessary in the hospital.
Otherwise, this can be addressed by his GP in regular hours.