To understand why combination therapies are your best bet in reducing hyperpigmentation, it's important to know what's going on under the surface of your skin. Special skin cells called melanocytes produce melanin, the natural pigment found in skin. Melanocytes do this by housing cellular vehicles called melanosomes, which are responsible for the first step in melanin production. When inflammation occurs (caused by the sun's powerful rays or a pimple-popping gone awry, for example), melanin production is triggered within melanocytes. This all starts with the enzyme tyrosinase, which turns the amino acid tyrosine into melanin inside melanosomes.

Once melanin is synthesized, melanosomes pass through the outer tips of melanocytes to transfer melanin (a process known as melanogenisis) into the other skin cells. The end result: more melanin, aka hyperpigmentation, which you might refer to as an age spot or acne scar.

We all have the same number of melanocytes, but the size and distribution of melanosomes vary from person to person; the larger and more clustered these melanosomes are, the darker the resulting spot will be.

According to Woolery-Lloyd, combination therapies are more effective because they attack melanosomes from a variety of angles. To give melanosomes that one-two-three punch, a successful combination therapy product typically contains:

1. A tyrosinase inhibitor (like hydroquinone) that suppresses the enzyme tyrosinase and keeps it from turning tyrosine into melanin.

2. An exfoliator that increases cell turnover to reveal newer, and thus more lightly pigmented, skin. Examples include retinol, glycolic acid and salicylic acid.

3. A melanogenesis inhibitor that stops melanosomes from transferring newly produced melanin to other skin cells in the body.

Woolery-Lloyd notes that some combination therapies also contain penetration enhancers such as kojic acid, which help topical treatments penetrate more deeply into skin. Combining this three-part formula with botanical ingredients and penetration enhancers is a more recent approach to targeting hyperpigmentation.

Best for: uneven skin tone and dark spots

Licorice: The extract from licorice root is naturally high in glabridin, a chemical compound that inhibits tyrosinase, the enzyme that kick-starts the discoloration process.

Glycolic acid: This chemical exfoliator removes the outer layer of dead skin cells, bringing fresh, new skin to the surface. Most over-the-counter skin care treatments usually have six to 10 percent glycolic acid. Chemical peels, which should be applied by professionals, have concentrations ranging from 20 to 70 percent.

Vitamin E: An antioxidant well known for its soothing properties, vitamin E protects against the sun's damaging rays while moisturizing and healing skin cells.

Best for: sensitive skin and sun damage

Licorice: This tyrosinase inhibitor is known for its soothing qualities, making it a good choice for women with sensitive skin.

Vitamin C: This antioxidant combats free radicals that can contribute to hyperpigmentation, such as UV rays, pollution and heat, and stimulates collagen production, which reduces the appearance of scars.

Niacinamide: This ingredient stops melanosomes from transferring melanin to surrounding skin cells while increasing skin's moisture and enhancing its barrier function.

Best for: dark spots from acne and oily skin

Kojic acid: It not only suppresses tyrosinase activity, kojic acide also helps topical treatments penetrate more deeply into the skin.

Arbutin: Extracted from the bearberry plant, arbutin is a natural alternative to hydroquinone. It curbs melanocyte activity and helps break down extra melanin in the skin.

Green tea: This natural, soothing antioxidant blocks free radicals.

Vitamin C: Also referred to as ascorbic acid, this antioxidant not only inhibits tyrosinase, it also treats oily skin by blocking pore-clogging debris.