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I received 26 very helpful replies. Many commented that the peanuts may have
been coated with a non-GF powder probably to prevent them sticking in
transit. Buckwheat may have wheat in it due to crop rotation on the farms
and stray wheat being harvested along with the buckwheat.

I heard from two of you who experience very similar neuro symptoms following
accidental gluten ingestion. It was comforting to hear that I am not alone!!
Thanks to you all.

Ruth (in Northern England)