Expired eyeshadow, like any other expired cosmetic product, can have several negative effects on your eyes.

1. Infection: The most concerning issue with expired eyeshadow is the risk of infection. Over time, bacteria and fungi can grow in the product, especially if it has been exposed to the skin and air. When applied to the eyes, these microbes can cause infections such as conjunctivitis (pink eye) or styes.

2. Allergic Reactions: Expired eyeshadow can also lead to allergic reactions. As the product ages, the ingredients can break down and change, potentially becoming irritants or allergens. This can result in redness, itching, swelling, or a rash on the eyelid or around the eye.

3. Reduced Efficacy: The pigments and binders in the eyeshadow can degrade over time, leading to a product that doesn't apply as smoothly or have the same color payoff. This may not harm your health, but it can certainly affect your look.

4. Dryness and Irritation: Expired products can lose their emollient properties, which can lead to dryness and irritation when applied to the skin. This can be particularly problematic for the delicate skin around the eyes.

5. Potential Chemical Changes: Over time, the chemical structure of the ingredients in the eyeshadow can change. This can lead to unexpected reactions when applied to the skin, such as burns or discoloration.

To avoid these issues, it's best to follow the product's expiration date and to store your cosmetics properly. Keep them in a cool, dry place, away from direct sunlight, and make sure to close the containers tightly after use. Also, avoid sharing your makeup to prevent the spread of bacteria and other microbes.