Dark armpits 10 months after my pregnancy and still darker. Any treatments to get rid of this problem please? (photos)

This is often genetic and due to hormones or rubbing but chemical peels and skin lightening often help.  Best, Dr. Emer.

This looks like a condition called acanthosis nigrans, make sure your internist screens you for diabetes or insulin resistance. This also tends to occur in families, and can be inherited. A glycolic cream 10-15% or Lac-Hydrin 12% lotion used daily will help, but can take 2-3 months of regular use for best results.