Solar urticaria (SU) is a rare and very disabling photodermatosis and generally demonstrates as urticarial wheals and erythema which appears soon after sun exposure. Often, SU is primarily diagnosed clinically with successive confirmation through photo-provocation tests. Primary diagnosis is essential for correct management of patients.

The assessment was done to display the clinical features of three cases of atypical presentation of SU and to review the possible underlying mechanisms.

A series of three patients who had presented with transient pruritic erythema without wheals were reported after sun exposure. All patients had undergone photoprovocation tests that were conducted to confirm SU diagnosis and also to define their action spectra. The results of treatment were recorded.

Within the UVA1 spectrum, all three patients developed classical manifestations of SU in the duration of photo-provocation tests. Two of them required high-dose irradiation to aggravate urticaria.

Thus, it is concluded that erythema without urticaria can be the initial and important manifestation of SU, especially in countries with sunny climates as natural skin hardening is very common. A high index of suspicion for SU cases is required and the importance of photo-provocation testing should also be highlighted to confirm the diagnosis.

Source: Azrielant S, Khanimov I, Sprecher E, Ellenbogen E. Transient Pruritic Erythema as a Forme Fruste of Solar Urticaria. Isr Med Assoc J. 2020; 22(4):227‐231.