If you aren't already, you need to wear sunscreen everyday. A lot of caucasian women feel that if they don't burn or not going to be in the sun much, they don't need sunscreen. Not so.
Though sunscreen may not completely prevent additional pigmentation, it does a little bit.
General unprotected exposure to sunlight causes pigmentation and freckling - just sitting in your car in traffic will do it. People that drive in traffic a lot and don't wear any facial SPF, you can see some freckling or a little wrinkling around their eyes. That's sun damage doing work on the bottom layers of skin.
As for getting rid of pigmentation, a natural alpha hydroxy acid, like lemon juice or apple cider vinegar helps fade marks. Here's some other fading remedies - this is from a document I created for my mom who has pigmentation problems on her back - so if some of this doesn't apply to you, ignore it. It's just a list of things that can work, it's not a recipe so don't mix them all together or anything!:
Various lightening ingredients
Vitamin C/Rose Hips
Cucumber juice/Lemon Juice
Niacinamide Cream - Buy Niacinamide capsules at any health store and break them open, add the powder from 5 x 500mg caps to 2 oz of your usual moisturiser.
exfoliating lactic acid
Natural Fix Recipe for Dark Underarms/Neck
"For dark underarms and neck apply lemon juice or lime juice mixed with cucumber juice and a pinch of turmeric daily. Leave it on your skin for 20 minutes!" That should do the trick without spending a lot of money on skin lightening products..It may take a bit longer but if you have the patience and the time this quick Fix will surely work for most. If lemon is too drying, put a little honey. (can use lemon/lime and cucumber juice only).
Uva Ursi (Bearberries)http://www.bastyr.edu/academic/botme...s_uva_ursi.asp
licorice, lemon, boric acid & cider vinegar
Tomato and Lime juices.
The treatment of acanthosis nigricans depends upon the primary cause which must be duly tackled. For local defects, salicylic acid ointment, retinoic acid, vitamins and thyroid may be tried.
There are some home remedies to whiten and soften the skin on your neck. You can make a skin tonic by mixing 3 teaspoons of borax powder, 2 tablespoons of glycerine and 2 cups of rose water. You can also apply this tonic on your arms and shoulders. We also have a recipe for an overnight cream for the neck, throat and shoulders. Mix equal parts of lanolin and butter. Beat them thoroughly in a double saucepan over boiling water. Rub this cream over your neck and shoulders in upward motions. Leave it on overnight and wash it in the morning.