Thanks for using Healthcaremagic,
After going through your available details it seems that you have allergy
to something it may be any food item like fish or egg.
Even it can be something else it is difficult to pinpoint one thing, as you said it disappears with antihistamine treatment which works well in allergy.
You should consult Physician/Dermatologist
and if necessary complete blood count
and serum IgE level and Allergy testing can be done to find out exact source of allergy.
If found specific it can be avoided and you will improve if not then also it can be treated with good medicine to give symptomatic relief.
One more thing if you have any bedbugs,pet animal please get rid of them.
Please keep your blood pressure well controlled and make sure it is not drug
which is causing allergy.
Hope this helps.
Wish you good health.
Dr.Akhilesh Dubey M.D.