Checking if your makeup has expired is a crucial step in maintaining healthy skin. Using expired makeup can lead to skin irritation, breakouts, eye infections, and more. Here are some steps to check if your makeup has expired:

1. Check the Packaging: Most cosmetics have a symbol on their packaging that indicates their shelf life. This is usually a small open jar icon, followed by a number and the letter 'M'. The number represents the number of months the product is good for once it has been opened. For example, '12M' means the product is good for 12 months after opening.

2. Note the Color, Smell, and Texture: If your makeup changes color, develops an odd smell, or the texture becomes clumpy or oily, it's likely expired. For example, mascaras tend to dry out and get clumpy, lipsticks can become hard and dry, and foundations can separate or change color.

3. Monitor Your Skin's Reaction: If you notice any irritation, redness, or breakouts after using a product, it may be expired.

Here are some general guidelines for the shelf life of various makeup products:

- Mascara: 3-6 months
- Eyeliner and Eye Shadow: 6-12 months
- Foundation: 1-2 years
- Lipstick & Lip Liner: 1-2 years
- Blush, Bronzer, and Powder: 1-2 years

Remember, these are just guidelines. Always check the packaging and monitor the product's consistency and your skin's reaction. Also, it's important to store your makeup in a cool, dry place away from sunlight to help it last longer.