Hello. I specialize in food sensitivity/intolerance testing so I hope this will be of benefit to you.
Hair analysis has not been studied (at least I could find no studies on it) with regards to food reactivity. You are right in that blood is more accurate, however IgG testing is not. This is because all foods will raise IgG levels according to scientific studies, both in cases of reactivity, but also mere exposure. You can google for studies on this.
After thorough research, the testing I finally chose to provide my own clients (I'm a nutritionist) is MRT. This is a mediator release test (via blood) which shows the level of mediators (immune chemicals) that are released by immune cells when exposed to a food antigen. 170 antigens are tested. It's very accurate and I see amazing improvements in my clients.
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