Vitamin C (L-Ascorbic Acid) in skincare can help with dark under eyes in several ways:

1. Brightening: Vitamin C is a natural brightening agent that can help reduce the appearance of dark circles by inhibiting the production of melanin, the pigment responsible for skin colour.
2. Antioxidant properties: Vitamin C neutralises free radicals that can cause oxidative stress, which can lead to dark circles and puffiness under the eyes.
3. Collagen production: Vitamin C is essential for collagen production, which can help improve skin elasticity and reduce the appearance of fine lines and wrinkles that can contribute to dark circles.
4. Hydration: Vitamin C can help improve skin hydration, which can reduce the appearance of dark circles and puffiness.
5. Inflammation reduction: Vitamin C has anti-inflammatory properties that can help reduce puffiness and discoloration under the eyes.