open sores on neck

Question
We have had 6 guinea pigs (2 females, 3 neutered males, 1 intact male) for almost 2 yrs now--very healthy, very active.  We live in a very hot, humid climate so we have them outside for much of the year, but bring them inside for about 3 mos (currently inside).  One of our neutered males developed sores only around his shoulders/sides of his neck.  They are definitely isolated to an area of skin that is about 10 cm wide x 2 cm long.  There are none under his chin or lower down on his torso/rump.  They are open sores and I assume they are from scratching.  Curiously though, we haven't witnessed any scratching on his part.  I did preventively bathe him for lice (we did not see any of the normal signs--dandruff, etc) and apply bacitracin.  Any ideas?  Most of the sores are healing, but there are 2 that are still open.  None have gotten infected, but they are red.  It really looks like a burn or when one removes a scab--red, skinless, no oozing or present bleeding.  Thanks for any help!

Answer
Hi Elizabeth
I am wondering if it is sunburn as you say you live in a hot climate.
I dont know what to suggest as you have already bathed him for lice.
Try putting some SUDOCREM on the red bits, its sold in UK for nappy rash in babies and sunburn. It has soothing properties and might help.