Confused about skin prick and blood test results

[Ruu]

My 6yo DS has been under a yearly review for his allergies since he was 2yo for sesame, nuts, egg, kiwi, avocado.
He had his skin prick test as usual but for some reason his results were way down from the previous year - some were even 0mm (compared to say 3/4mm the previous year).
The consultant was then keen to try some food challenges if the blood tests showed levels below 0.8 kual/l.
Fast forward to today and I pick up his blood results. Sesame was 14.9, peanut 3.11...the list goes on. There were only two nuts that were below 0.8.
How can the two be so mis-matched? We made sure we stopped his anti-histamine a good 5 days before the skin prick test.
I'll speak to the hospital in due course but wondered if anyone could shed some light?
Thanks!

[mamakoukla]

DDs allergist uses both but will only food challenge if blood results are down as these reflect circulating antibodies and likelihood of an adverse reaction

[mamakoukla]

Oops. Yes we have seen similar results but no harm to ask