When buying makeup, it's crucial to ensure that the products are not expired to protect your skin from potential harm. Here are some key things to look for:

1. **Manufacturing Date**: Most products have a manufacturing date printed on the packaging. This date can help you determine the product's age. However, remember that the shelf life of a product starts from the day you open it, not from its manufacturing date.

2. **Period After Opening (PAO) Symbol**: Look for a small open jar symbol on the product packaging. This symbol usually has a number followed by 'M' (e.g., 12M, 24M), which indicates the number of months the product is safe to use after opening.

3. **Batch Code**: This is a series of numbers and/or letters printed on the packaging. You can enter this code on cosmetic batch code checkers available online to find out when the product was manufactured.

4. **Consistency and Smell**: If you notice any changes in the product's consistency, color, or smell, it might be expired. For example, if a cream has separated into layers or a lipstick smells rancid, it's best not to use them.

5. **Packaging**: If the packaging is damaged, it might have exposed the product to bacteria, compromising its shelf life.

6. **Storage Conditions**: Products stored in hot or humid conditions tend to expire faster. So, if you're buying from a physical store, consider the store's storage conditions.

7. **Brand Reputation**: Reputable brands are more likely to follow strict manufacturing and storage guidelines, reducing the chance of selling expired products.

Remember, using expired makeup can lead to skin irritation, breakouts, and infections. So, it's always better to be safe than sorry when it comes to skincare and makeup products.