Well if I recall you said the areas disapear and show up in different locations? if so there are two things I *think* need to be checked further but first:
dark/black skin on a BD is one of two things that I know of:
1) reaction to light and heat -- turning dark to absorb more heat. thats normal and not part of forming any "Lumps".
2) injury to tissue, just like us if they get hurt they can get a discolored area a "bruise" they can heal the area and will then have dead tissue to "shed" if it's a surface injury.
so what is causing this tissue injury??
some possible causes:
1) not enough Calcium / UVB which gives them "Brittle / soft bones" that can break to easy and heal badly.
2) some object they are getting in contact with that is injuring them. can be a person handling wrong, another pet like a dog or cat, a sharp or pointed object they hit.
( see my last post on Dex and his "wall problems"
3) a burn; is there any way the areas could be from a heat lamp, heat rock or other such item?
4) some kind of infection of the skin.
5) neamatodes a parasite that can be in the skin of a lizard and will form some masses as they grow and multiply.
the bst thing will be to find a vet and get a "Hands On" checkup to rule out some of the things I am listing.
without seeing the problem and the environtment your lizard is in this list is just a guess....
try:
www.vetplace.com
or
http://www.herpvetconnection.com/
also post a new msg here asking for a vet near you.
also ask at any local pet shops that sell reptiles.
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