my rat has scabs all on her back

Question
hi there,
i was handling my pet rats the other day when i noticed my agouti dumbo rat has a lot of scabbing on her back, this must have been recent as i handle them every day and had not notcied it before.  Only things that have been changed is their food type and house bedding, could any of these be a factor, my other rat doesnt have anything of the same nature and look e perfectly healthy, should i get her to the vet or keep applying the antiseptic cream i am using and change their diet and house bedding back to what it was?
many thanks for your advice in advance


Answer
 The two most common causes of scabbing on the skin is an external parasite such as mites or lice or the other rat biting at her.  If you notice any red bugs on the skin, white nits (lice eggs) on her hair shafts, or she is scratching more than usual I would recommend treating her for parasites, applying a single drop of Advantage or Revolution (flea killer solutions for dogs and cats) to the skin at the back of her neck, then another in two weeks.  Even though the other rat isn't showing any signs of it you should treat her as well; the treatment is safe even if there are no parasites.  If this doesn't work and you haven't noticed them fighting at all it may be an allergy.  You can try changing their food and bedding back and seeing if that makes a difference.  Rats with allergies are pretty rare, though it can happen.  I wouldn't bother putting any cream on her unless directed by a veterinarian; it may do more harm than good.  Well I hope everything turns out, good luck with your rats!