My older daughter used to become violently ill (hives, fever and body aches including muscle cramps) when she ate any product with sodium nitrate. Many pork based products in the US are loaded with sodium nitrate.
She later started having life threatening reactions to all sorts of foods in her early 20s. Sweet corn, bell peppers, cayenne pepper, gatorade, etc.

Take care not to eat items that cause such problems. I would advise that you get yourself to an allergist.