Actinic keratosis (AK) is the main risk factor for the development of cutaneous invasive squamous cell carcinoma (SCC). It represents the first sign of severe chronic ultraviolet radiation exposure, which has a clear significant effect. Nevertheless, the skin is exposed to many other exposome factors which should be thoroughly considered. Our aim was to assess the impact of exposome factors other than ultraviolet radiation (UVR) on the etiopathology of AK and Bowen's disease (BD) and progression of AK to SCC and to design tailored prevention strategies. We performed an exhaustive literature search in September 2021 through PubMed on the impact of exposome factors other than UVR on AK, BD and SCC. We conducted several parallel searches combining terms of the following topics: AK, BD, SCC and microbiome, hormones, nutrition, alcohol, tobacco, viral infections, chemical contaminants and air pollution. Notably, skin microbiome studies have shown how Staphylococcus aureus infections are associated with AK and AK-to-SCC progression by the production of chronic inflammation. Nutritional studies have demonstrated how a caloric restriction in fat intake, oral nicotinamide and moderate consumption of wine significantly reduce the number of premalignant keratoses and SCC. Regarding lifestyle factors, both alcohol and smoking are associated with the development of SCC in a dosedependent manner. Relevant environmental factors are viral infections and chemical contaminants. Human papillomavirus infections induce deregulation of cellular proliferation and are associated with AK, BD and SCC. In addition to outdoor jobs, occupations such as industrial processing and farming also increase the risk of developing keratoses and SCC. The exposome of AK will undoubtedly help the understanding of its etiopathology and possible progression to

Introduction: Most skin disorders, such as atopic dermatitis, psoriasis, skin cancer or age-related skin issues, are the result of a complex interaction between genetic and environmental factors over time. As an external organ, the skin provides the opportunity to study the link between exposure to the environment and several specific biological responses using an exposome approach. The aim of this review was to identify the state of the art of exposome approaches and elucidate the impact of the new era of exposomics on dermatology. Methods: Two parallel and independent bibliometric analyses were conducted based on documents extracted from the Core Collection and the Science Citation Index Expanded (SCI-Expanded) databases from the Clarivate Analytics' Web of Science (WOS) platform by using the following search terms ''exposome'' and ''skin exposome''. In both searches, we used the topic field that includes title, abstract, author keywords and keywords plus terms and the following filters: ''English language'' and all documents published up to 30 September 2021. We further analysed and interpreted documents extracted in plain text format. Results: Based on the defined searches, 910 documents were identified as being related to ''exposome'' and 45 as being related to ''skin exposome''. Environmental sciences and toxicology were the most impacted research areas, and aging, cancer and respiratory allergies were the most documented diseases while, surprisingly, dermatology was much less impacted. Krutmann et al. were the pioneers in implementing this new concept in dermatology with publication of ''The skin aging exposome'' in 2017 (