The age at which it is safe to use lash serums can vary depending on the specific product and its ingredients. Generally, lash serums are designed for adults and are not recommended for use by children or teenagers. It is always advisable to carefully read the product instructions and consult with a dermatologist or healthcare professional before using any skincare or cosmetic product, including lash serums. They can provide personalized advice based on your age, skin type, and any specific concerns you may have.