Thanks for the query,
You might be suffering from cholinergic urticaria
or solar urticaria,
As you complain of itch and prick only in exposed parts of body.
Treatment can be oral antihistamines and topical steroids
Please meet a dermatologist
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.