My underarms are darker than the skin around it and it is because of hyper-pigmentation. I've had it for over 15 years and can tell you that shaving/waxing will not help it go away. If yours is a recent development you may be allergic to whatever hair removal technique you're using, like if you're using nair that contains harsh chemicals. Your doctor may be able to prescribe something.
The discoloration on any part of the body can be due to sun exposure, fungal infection and contact allergy especially to razor. It will be better option to visit a dermatologist for differential diagnosis and proper treatment. In natural remedies, treatment containing tea tree oil can be helpful.
They say use lemon juice
Dark under arms, neck and private areas is maximum due to over weight. If you are??? Then try to reduce the wait, then automatically your problems will be invisible, I can assure you about underarms and area around neck.....because I have faced the same problem......
1. Wash your underarms daily
2. Put a slice of raw potato under
your arm and rub gently.
3. You can use natural scrub
of orange juice, honey and sugar and scrub this with a slice of lemon.
4. Don’t use deodorants and
perfumes.
5. Don’t shave frequently.
If you don’t get results then
you should try Intilight. It is created by known dermatologist and it is
safe and effective method to lighten your skin naturally,
Underarms generally look dark due to thick hair, under the skin.You can treat them by shaving. Wax your underarm. It will take several times before your arm begins to get lighter. It depends on the person,regular waxing reduces hair growth. You may bleed a little. Don't worry.
To get rid of chafing you must apply Vaseline everyday. If the Vaseline doesnt work you need to try skin ointment. I had the same problem, I just applied the Vaseline and it slowly went away in a month... Many athletes get chafing.