Your condition could be described as an acute urticarial eruption if the lesions are red, itchy with central clearing and disappear in a few hours. Individual lesions do not last for more than 12 hours and new ones appear, and it seems they are always there.
is only plausible if this was after a new medication, food you have taken and happens within a few hours. Pain killers are notorious to cause these reactions, but if you have not taken before an outbreak it is unlikely to be an allergy
. However, medications can have a secondary effect on skin so do get your mdications reviewed if you are on any.
Urticaria is mostly non-alergic, although blood tests such as CBC, LFT, thyroid
are necessary at some stage especially if lond-acting antihistamines over 3-4 weeks taken daily do not help.