can occur due to number of reasons. It could be cosmetic, soap, detergent, chemical, clothing, plant, metal etc induced. To rule out the cause site of lesion, occupation, hobbies etc of the patient should be known. To pin point specific allergen a patch testing needs to be done with suspected allergens and the same can only be done by a dermatologist
or an allergy
The mainstay of treatment is oral and topical steroids
along with emollients and oral anti histaminics.
Unless the underlying cause is ruled out, treatment can only be offered to treat the existing lesions.
Hope that helps.