The research objective: Reactive skin induces cutaneous manifestations such as stinging, redness, dryness, and burning sensation in connection with the exposome. Its pathogenesis is mainly related to the dysfunction of neurosensory and also immune activity. Experimental methods: We evaluated the effect of polysaccharides extracted from Halymenia durvillei (Hd) on reactive skin, using an ex vivo model on inflammation and neurosensory discomfort. An in vivo study was also conducted on 25 selected volunteers with reactive skin. Clinical grading of facial skin including dryness, roughness, and erythema was assessed (SS-scale). Subject self-assessment questionnaires, photography, erythrosis were also included. Main observations: Hd extract was able to reduce the expression of TRPV-1 and NK1-R as well as to decrease TNF-α, and VEGF suggesting that this active extract may provide protection for sensitive and reactive skin from daily environmental agressions, named exposome. The in vivo study shows that Hd extract calms feelings of discomfort and redness, and controls the microvascularization. Volunteer’s questionnaire revealed self-perceived benefits consistent with expert visual grading. Conclusion: we show the efficacy of a new antireactive red marine algae rich in polysaccharides extract to protect the skin against the exposome. It will be interesting to evaluate whether this Hd extract can modulate skin microbiota, the relationship between skin microbiota and reactive skin having been recently reported.