Background: Arsenical keratosis is a precancerous dermatosis which could be induced by long‐term exposure to arsenic poisoning. Arsenic is often added to traditional Chinese medicine in a non‐compliant manner to increase the effectiveness of psoriasis treatment, which is often the main cause of arsenic poisoning in Chinese patients with psoriasis. Objectives: We performed a systemic review of arsenic keratosis during the past 32 years to better understand the sources, treatment, and prognosis of arsenic keratosis in China. Methods: We searched Medline/PubMed, Embase, CNKI, and Wanfang databases for research studies published between 1992 and 2024. A total of 64 papers with 78 individual Chinese of arsenical keratosis were included in this analysis. Results: Of the patients included in the analysis, 92.21% of arsenic poisoning was due to iatrogenic factors: Chinese traditional medicine. Seventy‐six patients (98.70%) had skin manifestation of hyperkeratotic papules and plaques, 68 patients (88.31%) had hyperpigmentation, 43 cases (55.84%) had hypopigmentation, and only 4 had a clear indication of Mees' lines in nails. A total of 52.63% of patients presented with tumors, including squamous cell carcinoma, Bowen's disease, and basal cell carcinoma. For patients with tumors, 20 opted for surgery, 6 for radiotherapy, and 3 for PDT. All patients with only cutaneous tumors are currently well‐controlled. Death occurred in one patient with metastatic squamous cell carcinoma. Keratinizing papules improved significantly in 70.59% of patients treated with Acitretin Capsules. Conclusions: In this study, arsenic sources in Chinese patients were mainly from traditional Chinese medicine, and there were no reports of exposure to water sources or occupational sources in the past 32 years. Most of the patients showed keratinizing papules and pigmentation, and more than 1/2 of the patients showed skin tumors, mainly squamous cell carcinoma. The treatments of tumors are mainly surgical treatment, PDT and radiotherapy can also be selected. The improvement in keratinizing rash was greater than 70% with acitretin capsules. Patients with this disease should be regularly followed up for early detection and timely treatment of potential malignant tumors.

Background: Scalp seborrheic dermatitis (SSD) is a chronic inflammatory skin disorder characterized by impaired barrier function and intolerance to topical products. However, the relationship between contact sensitization and scalp microbiota in SSD remains unclear. Methods: A total of 63 participants underwent patch testing with 62 allergens and were grouped according to the presence or absence of scalp involvement. Clinical assessments included symptom severity, transepidermal water loss, and stratum corneum hydration. Bacterial 16S rRNA V3–V4 sequencing and fungal ITS1 sequencing were performed in a subset of 36 patients with SSD to evaluate associations between allergen sensitization and scalp microbiota. Results: The most frequent sensitizers in patients with SSD were cobalt chloride, cetrimonium bromide, p-methylaminophenol, nickel sulfate, decyl glucoside, and minoxidil, although overall sensitization rates did not differ significantly between SSD and control groups. Specific allergens were associated with age, sex, disease duration, and disease severity. Increased transepidermal water loss was correlated with fragrance and preservative allergens. Minoxidil sensitization was negatively associated with Malassezia , whereas several fragrance and preservative allergens were correlated with Candida , Staphylococcus , and Corynebacterium . Conclusion: Patients with SSD showed distinct sensitization patterns associated with clinical characteristics, barrier dysfunction, and scalp microbiota alterations. These findings suggest that patch test reactivity in SSD should be interpreted in the broader context of allergen exposure, skin barrier status, and microbial imbalance.