Gluten Allergy

Hello everyone - I am still on the hunt to find out what is bothering my 3 1/2 year old. Right before he turned three he started breaking out in hives...particularly on his behind...but also showing up every where else. I use only all natural products for all my cleaning agents (detergent, household cleaners). Over the course of the past 6+ months his symptoms have been getting worse. He scratches his bottom until it bleeds, and he now has a couple scars because of it. He has projectile vomited on occasion, complains of tummy aches, gets racoon eyes, and is very hyper active. His stools are fairly normal though, maybe a little softer then usual, but solid. I have been to the doctor throughout this process...at first they thought it was excema because he does have dry skin and get patches of dry skin by the sides of his knees. So I have been doing all the appropriate treatments for that. I tried cutting milk out, and saw a minimal change. I was referred to a pediatric allergist. He ran a prick test, and he tested negative for any allergys. I was recently told by a friend to look into gluten. Her son has a gluten allergy, as does she. After talking to more friends I found others who suffer from this. I decided to cut out gluten for a week, and noticed that he wasn't scratching. I called my pediatrician. He told me that he thinks gluten allergys for the most part have become a "fad". He said there are people who suffer from real allergies from this but it is rare. He referred me for a blood test for celiac. He doesn't think my sons symptoms match this type of illness. My questions are these:

1. Will the fact that he hasn't eaten gluten for a week effect the test?

2. Does my sons symptoms sound familiar to any other moms?

3. What is the accuracy of this test?

I am feeling overwhelmed by this, and helpless to make my son feel better. Thank you for taking your time to read this, and for any insight you might have.