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Yes ,its a kind of allergy
called "urticaria" .And when you scratch and get red raised lesion that is called "symptomatic dermographism".Along with allergy it can be triggered by any infection in the body like infestation of worms in the stomach,bacterial infection in teeth or any fungal infection
on body.Even food items which you are allergic to can cause such kind of lesions.Stool examination is to see if you have any worms in the stool. In such cases better is to de-worm the patient by giving him albendazole
tablets.Along with this you would also require a long course of anti allergic medicines ,since it is difficult to find the exact cause of allergy.You should also rule any tooth decay and thyroid problem.It is at times associated with thyroid disease
. Couple ways to find out the allergen is - PRICK TEST & secondly immunological testing where in all food items are tested .
So,consult your dermatologist
with this back ground .I hope this would help you to understand your disease better.