Treat lupin as a risk until an allergist tells you otherwise. Lupin and peanut are both legumes with cross-reactive storage proteins, and studies put clinical lupin reactions in peanut-allergic people at somewhere around one in five, with sensitisation rates much higher than that. Reactions can be severe. Lupin is also a primary allergen in its own right, so people with no peanut allergy can be sensitised directly by it.

Lupin flour is naturally gluten-free, very high in protein, low in starch and gives a yellow, soft crumb, so it is used to add structure and protein to gluten-free and low-carb baking mixes. That is exactly the blind spot: someone avoiding wheat is often not scanning for a legume, and a coeliac who is also peanut-allergic can meet lupin in a loaf they assumed was the safe option.