There are many women as well as men who have melasma or dark spots from chronic sun exposure. Whether a slight case or one that is more severe, wearing a sunscreen everyday is a must. Even if you think you are "inside all day" or "it's raining today, so I don't need sunscreen". Ultravoilet light is present even if it's raining or snowing..... and goes through window glass.
When you read on a product, "SPF 20", it only refers to protection against UVB radiation and does nothing to protect from UVA radiation. UVA is highly implicated in skin cancer, dark spots, and aging. If you are only using the SPF rating to choose your sunblock, you are being misled. Sun protection needs to be "broad spectrum" which means covering both UVA and UVB rays.
There are two sunscreens that provide complete coverage of both these rays, Anthelios with Mexoryl and Neutrogena with Helioplex. However, sunscreens with borad coverage often leave a white, ashy residue on darker skin making the complexion appear sallow and unhealthy. Sunscreens with micronized titanium dioxide or zinc oxide minimize the white residue and are more appealing.
Similarly, new technology in cosmetics have been developed that contain a high SPF in a tinted base. A couple of my favorites are Revision Intellishade SPF 45, which is available in our office and Laura Mercier Tinted Moisturizer SPF 20. They both provide a small amount of tint to counteract the potential of looking sallow on darker skin tones. Both of these also offer an oil-free formulation which are great for acne prone patients.
In order to help your dark spots or melasma, you must be very vigilant about using sun protection 365 days a year. If you are seeing a dermatologist and receiving laser treatment, hydroquinone bleaching creams, retinoids or peels to treat these condition, your skin is even more susceptible to ultraviolet radiation.
My philosophy is: prevention is more important for the health of your skin than treatment. Practice sun avoidance and use the right sunscreen!