Your condition is called urticaria
and most people (80%) do NOT have allergies although the raised IgE level would suggest an underlying allergy.
Stress compounds the problem and causes the lesions to last longer but is not the cause.
You will need tests such as full blood count, iron levels, CRP, ANA, TSH fT4, TPO antibodies
to exclude a secondary cause.
Long acting antihistamines such as Allegra 180mg plus cetirizine
10mg in the evening for 4 weeks is recommended. For an acute generalised eruption that does not respond to antihistamines, you will need a short course of steroids (Omnacortil
40 or Prednisolone
40mg once daily after food for 5 days) as the last resort.
I hope this helps.