Generally, the shelf life of an unopened lipstick is three years, though this varies by brand. Once opened, the shelf life may be shortened due to factors such as environmental conditions and temperature. Most lipstick packaging features an icon of a small open jar, accompanied by a marking such as "12M," "18M," or "24M" (where "M" stands for "month"), indicating the product's shelf life after opening-12, 18, or 24 months, respectively.
It is recommended not to use expired lipstick. Lipsticks typically contain waxes, oils, and pigments that easily attract dust, viruses, bacteria, and other contaminants, potentially causing ingredients to degrade. Continued use can damage the skin cells of the lips, lead to oral or lip-related conditions, or pose health risks if ingested.