My 2 year old is allergic to Milk, Casein, Egg White, Egg Yolk, Wheat, Peanut, Soy, Banana, Coconut, Rice, Rye, Beef, all tree nuts, and lettuce. His problems began almost immediately. Colicky baby, vomiting, severe eczema, you name it.
I would assume that if you want to breastfeed him you would have to cut all of the allergic foods out of your diet. Did I read somewhere he's allergic to soy too? Something to keep in mind, your child is allergic to the PROTEIN in these foods. So, typically, if someone is allergic to soy, they can still have food prepared with soybean oil because the protein is broken down. My son is allergic to coconut, but obviously can drink Neocate even though it has coconut oil in it. Does that make sense? I hate to see people limit themselves more than they have to, especially when you are dealing with this many allergies.
Have you met with a pediatric dietitian in addition to the allergist? He/she will help you sort this out and verify what I've told you. The pediatric allergist and pediatric gastroenterologist I have met with all had a pediatric dietitian to meet with. She was invaluable.
In regards to NEOCATE, here is a form letter Dr's typically fill out and send to the insurance company. It's called a letter of medical necessity http://www.neocate.com/aaa_neocate/686-neocate-infant-req... . Be prepared to fight your insurance company to get them to pay. Perhaps you'll luck out, but people wouldn't be working so hard to get legislation passed to make insurance companies pay for Neocate and Elecare if ins companies typically paid for them. Neocate (and the US brand Elecare) are so broken down, they can be tube fed. The stuff tastes so bad, I don't think they ever intended for it to be tolerated orally. Insurance companies use this loophole to not pay for it. They say they will only pay for it if it is tube fed. I hounded my insurance company for months and finally refused to get off the phone one day until I got to speak to a manager. He worked with me to get it paid for. We were also reimbursed :). As an infant, it was running us $500/month, as a toddler it would have been around $350. My friend just got hers paid for by getting a lawyer involved.
I've known about my son's milk and soy allergy since he was couple months old, so I know what you're going through. It's so difficult to see them suffer.