There are several cases of hives that are referred to as “idiopathic,” due to the cause could not be determined.  Some outbreaks are caused by a viral infection, while others are caused by certain medications that the person has never been taken before. 

Certain medications such as aspirin, morphine, codeine, and other non-steroid anti-inflammatory medications, allow your body to release the histamine that produces urticaria with this non-allergic mechanism. 

Hives is a common skin disorder among several children and adults.  Even though hives have a reputation as being an allergen, when a person has no connection of using or have exposure to anything new, and they have a case of hives, the allergy tests are not helpful.

Some patients find it very frustrating not being able to determine what the leading cause is.  Therefore, it is not necessary to change your soap, diet, make up, nor detergent.