Chocolate, allergens and intolerances

True cacao allergy exists but is uncommon. Far more often the reaction is to something else in the bar: milk protein, soy lecithin, nuts, or wheat in an inclusion.

That matters practically, because someone who reacts to milk chocolate may be entirely fine with a two-ingredient dark bar.

This is the substantive risk for anyone with a serious nut allergy. Chocolate factories commonly run nut-containing products on shared lines, and may-contain labelling is widespread and genuine rather than defensive.

A plain dark bar from a facility that also processes hazelnuts is not safe for someone with a severe hazelnut allergy, regardless of its own ingredients. Dedicated allergen-free manufacturers exist and are the right answer where the allergy is serious.

Dark chocolate is often assumed to be dairy-free and frequently is not. Many dark bars contain small amounts of milk fat or milk powder, and many more are made on shared equipment and carry may-contain-milk labelling.

For lactose intolerance the amounts are usually trivial; for a milk protein allergy they are not. Reading the label is necessary rather than optional here.

Chocolate is frequently reported as a migraine trigger, and the relationship is genuinely unclear — some research suggests craving for chocolate may be part of the migraine prodrome rather than the cause, which would reverse the direction of the association.

This site does not resolve that. Anyone with a suspected food-related medical reaction needs a clinician and, where appropriate, allergy testing, rather than a general article.