How Frittu checks recipes against your allergens

Frittu uses a two-layer check on every recipe it generates. Before generation, Claude receives the user's allergen list as a hard exclusion instruction. After generation, a server-side scan checks every ingredient name against a coded keyword list — if a match is found, the recipe is rejected and regenerated before reaching the user.

These guides explain how that check works for each of the nine allergens Frittu covers — including the keyword lists, the hidden culinary sources, and the mechanism used to handle ingredient names that share substrings with allergen terms.

The first layer runs before generation. Every time Frittu builds a recipe, Claude receives the user's full allergen list as explicit exclusion instructions. The AI is told not to include any ingredient from those categories.

The second layer runs after generation. Once Claude returns a recipe, a server-side function checks each ingredient name against a per-allergen keyword list. Any recipe whose ingredient list matches a flagged term is rejected and regenerated automatically — without any action from the user. For a full account of how recipe generation and checking work, see How our recipes are generated and checked.