Woman with pruritic rash and dermatographism.

CASE PRESENTATION

A healthy 34‐year‐old female presented with 1 day of diffuse urticaria and dermatographism unresponsive to loratadine and diphenhydramine. The patient reported no apparent allergic exposures and denied dyspnea, wheezing, emesis, or angioedema. Recent history was notable only for Moderna COVID‐19 vaccine booster administered 10 days prior. Vital signs were normal. Examination revealed mild periorbital edema, dermatographism, and diffuse urticaria of extremities and trunk (Figure 1).

FIGURE 1

Spontaneous urticaria and dermatographism of the trunk on the day of presentation

DIAGNOSIS

Chronic spontaneous urticaria following mRNA COVID‐19 vaccination

The patient was prescribed diphenhydramine 50 mg every 6 hours and prednisone 40 mg daily. After allergist follow‐up 3 days later, the patient was prescribed an extended steroid taper, cetirizine, famotidine, and diphenhydramine. At day 23 follow‐up, the patient reported persistent symptoms on low‐dose prednisone (5 mg daily) and antihistamines (Figure 2). At day 42 (Figure 3), the patient was diagnosed with chronic spontaneous urticaria and her allergist prescribed omalizumab.

FIGURE 2

Urticaria and dermatographism of the back following 23 days of optimized pharmacotherapy

FIGURE 3

Pruritic dermatographism on day 42 of symptoms. At 6 weeks, the patient was diagnosed with chronic spontaneous urticaria and prescribed omalizumab

Up to 10.5% of patients experience cutaneous adverse reactions following COVID‐19 vaccination. , , Cutaneous manifestations are variable in appearance and time to presentation and may include urticarial, morbilliform, and vasculitic eruptions, as well as delayed localized injection site reactions and chronic spontaneous urticaria. , , , Chronic spontaneous urticaria is characterized by urticaria occurring on most days of the week over 6 weeks or longer. Therapy includes second‐generation antihistamines and avoidance of known triggers (eg, medications, stress). Refractory cases may require monoclonal antibodies and/or immunosuppressants. As mRNA vaccination campaigns expand, clinicians should be prepared to recognize and treat cutaneous adverse reactions, including chronic urticaria and dermatographism.