A tube of mascara lasts no more than 4 months after it is first opened. Compared to other beauty products, mascara is the most prone to bacteria growth, so an individual should pay close attention to the amount of time that has passed since the tube was used.
To remember when a tube was opened, users can write the date on a piece of tape and stick it to the tube. Using mascara for longer than 3 to 4 months allows potentially dangerous bacteria to grow inside the tube. If the bacteria comes in contact with eyes, it can cause itching, burning and even conjunctivitis.