Preventing mascara from smudging, especially brown mascara that can leave noticeable marks, involves a few key steps:

1. **Prep Your Eyelashes**: Before applying mascara, make sure your lashes are clean and free of any oils. You can do this by using a gentle cleanser or makeup remover.

2. **Use a Primer**: Using a lash primer before applying your mascara can help to create a barrier that prevents smudging. The primer also helps to lengthen and volumize your lashes.

3. **Choose the Right Mascara**: Opt for a smudge-proof or waterproof mascara. These formulas are designed to resist smudging and stay put throughout the day.

4. **Apply Mascara Correctly**: When applying your mascara, start at the base of your lashes and wiggle the wand up to the tips. This helps to evenly distribute the product and reduce the chance of smudging.

5. **Set Your Mascara**: After applying your mascara, you can set it with a setting spray or a translucent powder. This helps to lock the mascara in place and prevent it from smudging.

6. **Avoid Touching Your Eyes**: Throughout the day, try to avoid touching or rubbing your eyes. This can cause your mascara to smudge.

7. **Remove Mascara Properly**: At the end of the day, make sure to properly remove your mascara with a gentle makeup remover. Leaving mascara on overnight can lead to smudging and potential eye irritation.

By following these steps, you can help to prevent your brown mascara from smudging and keep your makeup looking fresh and flawless all day.