Acetyl tetrapeptide-40 is a synthetic peptide that has the ability to reduce the activity of pro-inflammatory cytokines IL-6 and IL-8, inhibit the release of inflammatory mediators and the activity of tyrosinase, thereby reducing pigmentation, capillary dilation and erythema caused by inflammation. In addition, it also has photoprotection function and can prevent skin inflammation caused by ultraviolet rays. Therefore, acetyl tetrapeptide-40 is suitable for the cosmetics field and plays an important role in after-sun repair, skin soothing and anti-aging products.