Yes, moisturizer with vitamin C is generally considered beneficial. Vitamin C is an antioxidant that can help brighten skin, protect against environmental damage, and boost collagen production, leading to a more youthful and radiant complexion.

The 'best' vitamin C face moisturizer depends on individual skin type and concerns. Look for formulations with a stable form of vitamin C (like L-Ascorbic Acid or Sodium Ascorbyl Phosphate) and consider factors like hydration level, added ingredients (like hyaluronic acid), and user reviews to find the optimal product.

While vitamin C is an antioxidant and plays a role in collagen synthesis, its direct impact on knee pain is limited. Some studies suggest it may help reduce inflammation, but it's not a primary treatment for knee pain; consult a doctor for appropriate treatment options.

Avoid mixing vitamin C with benzoyl peroxide or retinol in the same application, as these combinations can destabilize the vitamin C and reduce its effectiveness, potentially causing irritation. It's generally recommended to use these ingredients at different times of the day (e.g., vitamin C in the morning and retinol at night).