Yes, using expired makeup can potentially cause skin infections. The reason behind this is that over time, makeup can degrade and become contaminated with bacteria, fungi, and other microorganisms. These contaminants can lead to skin infections or irritations when applied to the skin.

The process of degradation is accelerated when makeup is stored in warm, humid environments or when it comes into contact with the skin or mucous membranes. This is because these conditions are conducive to microbial growth.

In addition, the preservatives in makeup, which are added to prevent microbial growth, can also degrade over time, reducing their effectiveness.

Symptoms of a skin infection caused by expired makeup can include redness, swelling, itching, and in severe cases, pus-filled blisters.

Therefore, it's always a good idea to follow the expiration dates on your makeup products and to store them in a cool, dry place. Also, avoid sharing makeup as this can increase the risk of contamination.