Dark vulva

Question
Hello.  My 10 month old puppy is currently going through her first heat.  The vet and I decided to let her go through her first heat to try and clear up an underlying condition.  She's at about 21 days now, and her vulva is almost back to the size it was before she began her cycle.  But my question is this: the skin of the vulva is very dark.  The rest of her skin is pink.  Is this due to her still being in heat?  Will the skin go back to the color it was before?  Thank you for your time.

Answer
I think the vulva does tend to lighten a bit when it is swollen, usually becoming fairly pink. When the swelling goes down, the vulva is then darker because the extra blood levels have dropped. Also, skin that is exposed to the light for a few days will tend to darken, so if your dog is a bit hairy, the vulva should lighten a bit if the hair covers it again.