Unilateral rosacea is a rare type of rosacea that affects only one side of the face. Limited literature exists on this condition which resembles classic rosacea with persistent erythema, papules, or pustules but shows an unusual asymmetric pattern. The cause is unclear though localized triggers or vascular differences may be involved, complicating diagnosis due to similarities with other conditions.

This is a case of a 42-year-old male who presented with a 4-year history of few ill-defined erythematous patches topped with yellowish papules on the right side of his face and neck. On initial consult, he was noted to have a history of prolonged esun exposure. A skin punch biopsy was done and revealed basal layer hyperpigmentation, pigment incontinence and lymphohistiocytic cell aggregates in the dermis, consistent with granulomatous dermatitis. There was no Demodex infestation. Based on clinical and histopathological data, the diagnosis was unilateral rosacea. Treatment in this case included topical Azelaic Acid cream and frequent sunscreen application along with physical photoprotection, avoidance of unnecessary and prolonged sun exposure.

First reported in 1989 by Shelley et al., unilateral rosacea is underreported, making it challenging to estimate its prevalence. It affects middle-aged adults and can be confused with other unilateral skin conditions. However, no specific data or large-scale studies have been dedicated solely to unilateral cases and it may be mistaken for other unilateral skin conditions making the diagnosis challenging. Treatment generally follows the rosacea protocols like topical therapies, oral medications and lifestyle modification.