Sanitizing your blush stick is an essential routine to maintain good hygiene and prevent the spread of bacteria. Here's a simple step-by-step guide:

1. Start by washing your hands thoroughly. This is to ensure that you don't transfer any bacteria from your hands to the blush stick.

2. Next, you'll need a high-quality cosmetic sanitizer spray. These sprays are specifically designed to kill bacteria on makeup products without affecting their performance.

3. Hold the blush stick and spray the sanitizer directly onto the product. Make sure you cover the entire surface area.

4. Let the blush stick air dry. This usually takes a few minutes. Do not wipe it dry as this can spread bacteria and also remove the sanitizer before it has had a chance to work effectively.

5. Once dry, you can close the blush stick and store it in a clean, dry place.

6. It's also important to clean the cap and the outer surface of the blush stick. Wipe them down with a cloth sprayed with the same cosmetic sanitizer.

Remember, it's recommended to sanitize your blush stick at least once a week if you use it regularly. If you're using it less frequently, sanitizing it after every few uses should suffice.

It's also worth noting that makeup products do have a shelf life. If your blush stick is past its expiration date, it's best to replace it. Old makeup can harbor bacteria and may not perform as well.