[Suspected allergic reaction during anesthesia requires thorough postoperative investigation]. / Allergisk reaktion i forbindelse med anæstesi kræver grundig postoperativ udredning.

Allergic reactions during anaesthesia are rare and the cause is seldom immediately obvious. Incorrect guesses for the offending substance can lead to suboptimal management. Furthermore there is a risk of a serious reaction on subsequent exposure to the real allergen. We present a case of suspected allergy to fentanyl investigated at the Danish Anaesthesia Allergy Centre. Allergy to this drug could not be demonstrated by skin tests or challenge. The reaction was due to unspecific histamine release induced by several opioids given at the same time. Future pretreatment with antihistamine was recommended.