White vinegar and nicotinamide are considered to have certain freckle removing effects for the following reasons: the acidity of white vinegar and the antioxidant effect of nicotinamide.

1. Acidity of white vinegar: White vinegar contains acetic acid, which makes it acidic. Acidic components can help remove dead skin cells on the skin surface and reduce the exposure of pigmentation. In addition, acidic components can also promote skin metabolism and cell regeneration, which helps to dilute pigmentation.

2. Antioxidant effect of nicotinamide: Nicotinamide has antioxidant effect, which can help reduce the damage of free radicals to the skin. Free radicals are one of the main causes of skin aging and pigmentation. Through antioxidation, nicotinamide can reduce pigmentation and improve uneven skin color.