A 30-year-old female patient developed a butterfly-shaped rash on her face after prolonged sun exposure.

A 30-year-old female developed butterfly-shaped facial erythema after prolonged sun exposure, which may be related to physiological or pathological factors. Pathological causes include solar dermatitis and systemic lupus erythematosus, among others. Treatment should be tailored according to the underlying cause. Detailed analysis is as follows:

I. Physiological Factors

Infrared radiation in sunlight produces a thermal effect. Long-term exposure can lead to facial skin capillary dilation and redness due to congestion, which is a normal physiological response. This typically resolves spontaneously once sun exposure is avoided.

II. Pathological Factors

1. Solar Dermatitis: Also known as sunburn, this is an acute skin injury caused by intense sunlight and excessive ultraviolet (UV) radiation beyond the skin's tolerance. Under medical guidance, topical treatments such as tacrolimus ointment or vitamin E ointment may be used to reduce inflammation and promote skin recovery.

2. Systemic Lupus Erythematosus (SLE): Patients with SLE are photosensitive, and UV exposure can exacerbate immune dysfunction and worsen facial rashes. The characteristic skin lesion is a butterfly-shaped malar rash, typically starting on both cheeks and the bridge of the nose. Under professional medical supervision, patients may take glucocorticoids such as methylprednisolone tablets, and appropriate immunosuppressants such as hydroxychloroquine tablets or cyclophosphamide combination tablets based on disease severity.

In addition, other possible causes include seborrheic dermatitis, contact dermatitis, and skin tumors. Patients are advised to seek timely medical evaluation and treatment.