You can't test immune reactions via a hair sample, and in many cases there have been discrepancies in results when parts of the hair have been coloured/bleached. This has led to inconsistency in the sample tested twice.
Our IgG 1,2,3,4 blood based testing covers the full range of antibodies responses, this is important, if a particular food elevates any antibodies against it, this means your gut and immune system recognises that food as a threat. This could affect the nutrients absorbed from this particular food and leads to multiple symptoms,