Absolutely, you can use brown mascara with black eyeliner. This combination can create a softer, more natural look compared to using black for both. The contrast between the two colors can also help to make your eyes stand out more.

The black eyeliner will define your eyes, while the brown mascara will give your lashes a softer, more natural look. This is especially beneficial for those with lighter skin tones or hair colors, as it can provide a more balanced look.

However, it's important to remember that everyone's skin tone and personal style are different. What works for one person may not work for another. It's always best to experiment with different combinations to see what works best for you.

In terms of ingredients, both mascara and eyeliner, regardless of color, should be chosen with care. Look for products that are free from harmful chemicals and are enriched with nourishing ingredients. For instance, mascaras with natural oils like castor or almond oil can help to nourish and strengthen your lashes. Similarly, eyeliners with ingredients like jojoba oil or vitamin E can be gentle on the sensitive skin around your eyes.

Remember, the key to great makeup is not just about the colors you choose, but also about the quality and safety of the products you use.