Transient Pruritic Erythema as a Forme Fruste of Solar Urticaria

Solar urticaria (SU) is a rare and disabling photodermatosis. SU typically manifests as urticarial wheals and erythema appearing shortly after sun exposure. SU is often initially diagnosed clinically with subsequent confirmation through photoprovocation tests. Early diagnosis is important for correct management of patients.

To present the clinical features of three cases of atypical presentation of SU and to discuss possible underlying mechanisms.

We report a series of three patients who presented with transient pruritic erythema without wheals after sun exposure. All patients had photoprovocation tests conducted to confirm SU diagnosis and to determine their action spectra. Treatment outcomes were recorded.

All three patients developed classical manifestations of SU during photoprovocation tests within the UVA1 spectrum. Two patients required high-dose irradiation to provoke urticaria.

Erythema without urticaria can be the primary manifestation of SU, especially in countries with sunny climates where natural skin hardening is common. Such cases require a high index of suspicion for SU and highlight the importance of photoprovocation testing to confirm the diagnosis.