Summary

Coffee comes from roasted seeds of trees of the Rubiaceae family. It is consumed by hundreds of millions of people worldwide due to its pleasant taste, aroma, stimulant effect and health benefits. Allergy to coffee consumption is rare, and the few clinical cases reported are likely due to other ingredients contained in the beverage, rather than to the coffee bean itself. However, in processing the 9 million tons of coffee produced each year, many coffee workers are exposed to irritating and sensitizing dust. This represents a common occupational allergy and some cases are attributable to coffee bean dust in particular.

Epidemiology

Worldwide distribution

Allergic reactions to the ingestion of coffee are appear to be rare and the results of the association between coffee consumption and asthma is inconsistent.

Coffee is consumed by hundreds of millions people worldwide with about 9 million tons being processed every year. The processing includes removing pulps and drying the resulting green coffee beans by sunlight. Usually the beans are then roasted and/or decaffeinated and shipped worldwide. About 25 million coffee workers are exposed during the coffee processing to irritating and sensitizing dust with several additional allergens (including burlap and cockroach). Dust from coffee bean processing has been reported to elicit skin, ocular, and respiratory allergic reactions in up to 50% of coffee processing industry workers.

Clinical Relevance

Allergic reactions to the ingestion of coffee are rare and several studies indicate a beneficial effect in some asthmatic patients. Case reports of allergic symptoms after coffee consumption have been attributed to other constituents, such as the preservative sodium metabisulphite, and to cow’s milk and/or sodium caseinate.

Allergic symptoms to caffeine have been reported in a small number of patients after consumption of coffee. Despite a lack of clinical reports investigating coffee allergy, one study including 150 people from Iraq showed that 25.7 % had positive coffee skin prick tests.

Cross-Reactivity

One study examined the cross-reactivity between extracts of various coffee beans and dust as well as with castor bean, which is another suspected allergen in the coffee processing industry. However no evidence of cross-reactivity was found with the roasted coffee beans.