What causes shellfish intolerance?
A shellfish intolerance occurs when your digestive system does not have the appropriate enzymes to break down shellfish protein, producing an inflammatory response and difficulty digesting. This is different from a shellfish food allergy, which induces adverse reactions as a result of the body’s immune system. Allergy reactions tend to be more serious and could be life-threatening, especially if they cause an anaphylactic reaction affecting the respiratory system.
Whilst you need to actually eat shellfish to experience intolerance symptoms, with a shellfish allergy, you can experience symptoms from just touching or cooking shellfish, depending on the severity of the food allergy.
It’s also important to note that one-off digestive reactions to shellfish could also stem from food poisoning rather than a food intolerance (if the shellfish is appropriately prepared or not fresh). It is for this reason that it’s a good idea to keep a food diary to monitor offending foods.