Using expired makeup is not advisable, and here's why.

Every cosmetic product has a shelf life, which is typically indicated on the packaging by a symbol that looks like an open jar with a number, followed by the letter 'M'. This symbol represents the 'Period After Opening' (PAO) and indicates the number of months the product is safe to use after it has been opened.

When makeup expires, the preservatives that prevent the growth of bacteria and fungi start to break down. This can lead to contamination of the product, which can cause skin irritation, infections, or allergic reactions.

Moreover, expired makeup may not perform as intended. The color may change, the texture may become clumpy or dry, and the product may not spread evenly on the skin. In the case of sunscreen-containing products, the efficacy of the sun protection factor (SPF) can decrease over time, leaving your skin vulnerable to harmful UV rays.

Here's a general guide to the shelf life of various makeup products:

1. Mascara and Eyeliner: These products have the shortest shelf life, typically 3-6 months. This is because the risk of transferring bacteria from your eye to the product and back is high.

2. Foundation and Concealer: These can last for up to a year. If you notice any change in smell, color, or texture, it's time to replace them.

3. Lipstick and Lip Gloss: These products can last for up to 2 years. However, if you notice any changes in smell or texture, or if the lipstick becomes dry and hard to apply, it's time to throw it away.

4. Powder-Based Products (Blush, Bronzer, Eyeshadow): These products can last for up to 2 years. Since they don't contain water, they are less likely to grow bacteria. However, if the product becomes hard or changes color, it's time to replace it.

5. Brushes and Sponges: Brushes should be cleaned at least once a month, and sponges should be replaced every 3 months. Regular cleaning can prevent the buildup of bacteria and extend the life of these tools.

Remember, these are general guidelines and individual products may vary. Always check the PAO symbol on the packaging and pay attention to any changes in the product's smell, color, or texture. When in doubt, it's always safer to replace the product.