Anaphylaxis in which no triggering cause can be demonstrated is called idiopathic anaphylaxis (IA). Idiopathic anaphylaxis is a lifethreatening disease with symptoms similar to other forms of anaphylaxis. Although rare, it is clinically important due to the risk of morbidity and mortality. There is currently no standard long-term prophylaxis regimen for IA. The use of omalizumab was beneficial in some patients who did not respond to treatment.

We report a 16-year-old girl with chronic spontaneous urticaria who was later diagnosed with IA and was successfully treated with omalizumab. Subcutaneous omalizumab treatment was started in our patient who did not respond to antihistamines and mast cell stabilizers. Omalizumab treatment was initially started at 150 mg/month and the dose was increased to 300 mg/month when the attack recurred.

Allergists should keep in mind that patients with chronic spontaneous urticaria might develop IA, which is responsive to omalizumab.