Flushing and pruritus secondary to prescription fish oil ingestion in a patient with allergy to fish

Background A brand of fish oil capsules contains omega-3 fatty acids obtained from several fish sources. Although the manufacturer calls for caution in patients with fish hypersensitivity, insufficient data is available to make a definitive recommendation regarding its use in this population. Case presentation A patient with documented seafood allergy presented to the emergency department 4 days after the initiation of prescription brand name fish oil capsules complaining of chest tightness, shortness of breath, tingling of upper extremities, flushing, and pruritus that was minimally relieved by excessive nonprescription diphenhydramine administration. During subsequent follow-up, the patient reported that all symptoms had resolved within 5 days of discontinuing the medication and 3 days of disposing of her pillbox and all medications that had come in contact with the fish oil capsules. Conclusion Due to the patient’s allergic history, timing of onset/offset of the reaction, laboratory evidence, and the use of the Naranjo probability scale, prescription fish oil capsules were deemed the probable cause of this patient’s pruritus and flushing of the face and trunk. Practitioners and patients should always ensure they have an updated list of allergies within the patient’s medical record that includes medications as well as foods and food additives.