4-Methylbenzylidene camphor (4-MBC) is a photo-absorbing UV filter, which can be absorbed into the circulation and cause systemic effects. 4-MBC is found extensively in the environment and measurements suggest bioaccumulation in human tissues. 4-MBC is continued to be released in the environment despite the growing knowledge about its potential endocrine and reproductive disrupting effects. 4-MBC interfers with various processes, such as placental development, spermatogenesis, and inflammatory cascades. Previous reviews mention 4-MBC as one of the several UV filters but here we focus on 4-MBC only. We cover the potential effects on human health regarding systemic and molecular effects, with the focus on reproduction. We also cover the potential bioaccumulation and interactions with receptor systems, such as the estrogen receptors β and α, and progesterone receptor, and analyze 4-MBC´s effects on mRNA expression and protein expression. Furthermore, 4-MBC is reported to act with inflammatory pathways by activating p38 MAPK and NF-κB, leading to the production of inflammatory TNF-α and IL-6. In conclusion, 4-MBC has wide ranging effects in different models while there is more research warranted to detail the mechanism of action, long-term effects at low doses and the potential interaction with many pathways and other pollutants.

4‐Methylbenzylidene camphor (4‐MBC) is a photo‐absorbing UV filter prevalently used in cosmetics, which can be absorbed into circulation and cause systemic effects. 4‐MBC is continued to be released in the environment despite the growing knowledge about its bioaccumulation and endocrine disrupting effects. Previous reviews have mentioned UV‐filter together but this review considers 4‐MBC alone, due to its prevalence and concerning health effects. This review considers 4‐MBC's potential effects on human health regarding systemic and molecular effects, with the main focus on reproduction. Also, the potential bioaccumulation and interactions with receptor systems such as the oestrogen receptors β and α, and progesterone receptor are covered. Additionally, previous studies about 4‐MBC's effects on mRNA and protein expression, especially in the prostate and the brain are analysed. Furthermore, 4‐MBC is reported to act with inflammatory pathways by activating p38 MAPK and NF‐κB, leading to the production of inflammatory TNF‐α and IL‐6. 4‐MBC was also found to induce apoptosis and inhibit cell proliferation and DNA repair. In conclusion, 4‐MBC has wide‐ranging effects in many different models interacting with multiple pathways causing long‐term effects even at low doses and this knowledge can guide governmental risk assessment, regulation divisions and chemical industries.