Hello and welcome to healthcaremagic
I would keep a possibility of Dermographism. It presents as itching and skin welts/swellings along scratch lines.
Urticaria OR hives can occur due to various causes like(to name a few):
--Infections(bacterial , viral, fungal)
--Drugs(Pain killers/ antibiotics etc)
--Certain foods and food additives/preservatives
--Physical Urticaria: Cold temperature, Heat, Pressure(Prolonged Standing, Sitting), Dermaographism etc.
--Cholinergic Urticaria: in response to strong emotions, exercise, spicy food etc --
Autoimmune disorders like SLE, RA etc.
--A few cases have no underlying cause and are known as idiopathic urticaria.
I would advice you to get few basic lab tests like Hemogram, stool for ova/cyst, Urine routine, Chest X-Ray.
An oral antihistamine like
Fexofenadine (Allegra 180 mg tab) OR
Loratadine (Alaspan 10mg tablet) once or twice daily for a week would be suitable. They are non-sedating and wont affect your alertness level.
A topical soothing lotion like
calamine would help you symptomatically.
take care
regards