Vitamin A (retinoid)
What it does: Fades brown spots and smooths roughness.
How to use it: Apply retinoids lotions or creams only at night, since sunlight inactivates most forms of vitamin A. Prescription retinoids work fastest, within four to eight weeks.

Vitamin B3 (niamcinamide)
What it does: Helps increase skin hydration, makes skin less irritable and reduces dark spots.
How to use it: For maximum results, apply B3 vitamins twice a day. To reduce irritation from your retinoid, use the lotions, creams or serums in conjunction with niacinamide by mixing them together in the palm of your hand before applying.

Vitamin C
What it does: Helps smooth the skin and fades dark spots. It also destroys the free radicals that trigger sagging and other aging changes.
How to use it: Apply vitamin C serums and moisturizers in the morning before applying sunscreen.

Vitamin E
What it does: Prevents dryness by helping skin retain its natural moisture, neutralizes damaging free radicals, and boosts the skins’s UV defenses.
How to use it: Follow the instructions for the particular product you’re using, and be sure to apply before sun exposure.

Vitamin K
What it does: Reduces dark circles under eyes
How to use it: Apply the eye cream at night.