This is very serious, as you know, and you certainly need continued, intensive medical assistance, as you are following. It also makes sense to be reaching out to other directions to see what could possibly be missed.
Has she had any fevers? Dou you have a current hemoglobin level?
I have another chief question. The standard meaning of exclusive breastfeeding is no formula or solid foods of any kind. Some use the term just to mean no formula, while they are providing solid foods. My question is, when did solid foods and/or formula begin, what kinds, and how much. If they truly began after 12 months, then there is a greater possibility that she’s reacting severely to certain foods. You are already avoiding some key allergens, but I’m concerned about gluten, specifically, and very likely, other foods. Rather than just adding gluten to your list of foods to avoid, you truly need to eliminate all possible allergens, now.
Medically, even though there is clearly regular blood loss through the stools, your child should still be evaluated for bone marrow disorders. It’s most likely this has been done, as it’s mostly a matter of simple, specific blood tests. Lead levels should be tested as well. I am absolutely no medical doctor or GI specialist but, unless another answer is found quickly, you absolutely need to see the rest of your baby’s intestinal tract. There are lots of options; barium studies, a little camera in a capsule that is swallowed, CT scans, and MRIs. Again, I don’t know what can and can’t be done at her age, but if her doctors are not going there, you need to find someone else who will, or who will provide strongly convincing reasons not to.
Because there have been such positive food allergen tests, I would certainly want to find out whether this is all food related, but I wouldn’t want to wait too long to look at the rest of the GI tract. Since your doctors seem comfortable in waiting, then it’s your decision whether you want to give diet a try for a little while or pursue other medical tests quickly. Since these tests seem to take so long to get rolling, I might personally work soon on pushing for more GI diagnostics, while immediately eliminating all potential allergens, and then finding a yardstick to measure dietary success before actually doing more invasive tests (while I do not consider MRI to be invasive).
Allergist visits are good and fine, but you must understand that negative IgE or other tests do NOT mean there is no other allergy or intolerance to other foods going on. Even negative wheat or specific celiac disease tests do not mean a child is not reacting to gluten – a common cause for anemia. There are many factions to the immune system that are known to be involved in abnormal food responses, including IgG, IgM, and IgA antibody actions, T cells and other lymphocytes, and much more. Blood and scratch tests can give some helpful hints, but only food avoidance tests can provide true diagnoses.
At your child’s severity, I would go for a total elimination diet. If you are still nursing at all, you will need to avoid allergens yourself, but your milk could be an absolute lifeline for her recovery from whatever is going on here. Let me know about this point and then we will talk more about it.
Since you are feeding Neocate, this is a good alternative for a nearly allergen-free diet. The only frustration with it is that it still contains traces of corn proteins – out of sheer ignorance and cost-cutting (it used to not be there). There is no perfectly hypoallergenic formula available today in the U.S. Liquid Alimentum contains no corn, but it is hydrolyzed milk rather than the basic amino acid formulation of Neocate. Hydrolyzation is not 100%, leaving traces of milk proteins that many babies still react to. If your child’s problem truly is food reactions, then it is severe enough that I would expect her not to tolerate hydrolyzed formulas, but it’s a possible trial option, down the line. It’s clear that some babies react to Neocate even when we’ve discovered that they are tolerating corn just fine. I suppose it’s something to do with all the chemical processes used to create each synthetic ingredient. I can’t say what, specifically, but I’ve certainly seen it. One final option would be re-lactation/upped lactation or usage of donor milk from a mother eating for a highly allergic baby. I could help you find it.
At this point, I am recommending a trial 100% Neocate diet. Mixing Neocate with other solid foods only complicates the picture and it provides ample nutrition by itself. Nutritionally, coconut milk is pretty void, except for healthy fats. There’s no reason to be adding fat to formula though, as formula has the proper proportion of fats, carbs, and proteins, and more fat isn’t what your baby needs. Since she’s shown a strong nut allergy, coconut is a nut, of sorts, and not particularly non-allergenic. I’d skip it, personally. I’d go with nothing but Neocate, (and cow’s milk, gluten, and other allergen-free breastmilk – talk to me about that), and watch for any signs of improvement, and then if that’s not working, I can help you to design a nutritious elimination diet, beginning with only a few nutritious low-allergen foods, and using no formula at all.
Please look carefully back over the non-dairy, etc. diet you have been providing and determine whether she’s actually been maybe 95 or 99% free of these foods (no traces of whey, casein, butter, yogurt, or cheese, for example) or truly 100%. It’s OK (maybe/probably) when things only say that they were made on equipment that is shared with milk, nut, etc. products. Also let me know about her grain consumption. I’m interested in what solids you have been feeding, and what supplements, including your iron supplements, you have been providing.
Are there any other signs of food reactions? The green stools are a hint – how often do you see green? How about diarrhea, gas, colic, spitting-up, diaper rashes, a bright red ring around her anus, or eczema anywhere? How much does she cry? It takes a “long” time for hemoglobin to go up, so we need to find a better yardstick for determining improvement with dietary trials. For one, there are home stool blood tests available. I'd get hold of some.