Itchy Chihuahua

 Welcome to idog; Jessie has food and environmental allergies so I can sympathize with you. It could very well be a food allergy. If you are going to change her food it is important to make sure the new food doesn't have any of the ingredients of the old food. I know the first ingredient in Science Diet is corn so that's a good suspect; if chicken is in the ingredients it's a likely suspect too. You can do a google search and learn about these foods; Natural Balance and Eagle Pack Holistic. Both companies make foods with ingredients for dogs with allergies; Jessie is eating Eagle Pack Holistic Fish and Oatmeal but many here have had good results with Natural Balance. You can find these foods at feed stores. Since your dog has been on her old food so long it's hard for her to accept a new food. You need to slowly mix the new food into the Science Diet taking at least a week to have her totally on the new food; mixing a little canned food in can help the adjustment by making the food seem more appealing and canned food is very good for dogs.
   There are better shampoos than oatmeal shampoo. There is one called Nu Sal T and you may have to order it online; another good one is Nova Pearls and should be at PetsMart or  etco. There is a conditioner that is also excellent; you should be able to find it at PetsMart or Petco; it's made by Tropiclean and is called Oxy Med; it has either a red or blue cross on the bottle and you must leave it on for the time stated on the bottle before rinsing for it to help. Good luck with your girl; she's a cutie. []
 

Thanks for the suggestion we're going to try those shampoos you recommended.  We're acturally trying to switch her her over to natures recipe because there's one that doesn't have corn, wheat or beef and we were reading up on allergies and chihuahua are most commonly allergic to corn and beef so we're going to try this one first it does have chicken in it and so does her current food, so if we can at least get her switched over than if it doesn't get any better I'll find something that doesn't have chicken in it.  I know she won't eat anything with fish in it, the vet gave us some food and it has fish oil and she won't go near it.  But thank you for making me aware of the chicken.  Now the hard part is just to get her to eat the new food, we've tried giving her the new food mixed in with the old food and reducing the old food each day, but she acturally icks out her old food and just eats that.  We than tried to just give her the new food altogether and figured she'd get hungry eventually and eat, but she acturally went two days without really eating anything, just drinking water and maybe eating a piece here and there, no one gave her treats or anything else, but we finally broke down and gave her, her old food back because we knew she must be hungry and her tummy was grumbling, but she just flat out refused to eat it. Than she actrurally wouldn't eat her old food either for about an hour or so, but than she finally went back to eating it.  Talk about stubborn.  But were going to try again with mixing it.   

Eagle Pack makes a food with duck and one with lamb; neither have corn; Natural Balance makes foods with venison and duck ; they don't have corn either. You can check with your vet but I think your dog can go at least three days without eating although it sounds harsh; if you mixed some canned food with the dry that probably would do the trick; good luck. Antihistamines can help with the itching too; here's a link for ones safe for dogs with dosages by weight;
                                      [linkhttp://www.utskinvet.org/pdf/antihists.pdf]http://www.utskinvet.org/pdf/antihists.pdf[/link]
 
 It can take a week to tell if an antihistamine is helping and you may need to try several before finding one that works. Good luck.