COMMENTARY

Eating Insects, Even by Accident, Carries Notable Allergy Risks

Gary J. Stadtmauer, MD

Disclosures

October 23, 2018

In the midst of a food allergy epidemic, it is important to be aware of all of the possible allergens that people eat, knowingly or unknowingly.

About 2 billion people on the planet eat insects, with about 2000 species ingested in Latin America, Africa, and Asia.[1] The most commonly ingested insects, in descending order, are beetles (31%), caterpillars (18%), stinging insects (ant/wasp/bee, 14%), locusts/crickets (13%), and cicadas (10%).[1] Farther down the list are termites (3%) and flies (3%), which seem to be the least appetizing of the insects.

There are a number of case reports but few published studies on this topic. In Laos, about 8% of insect eaters are allergic to this food, and surprisingly, in China, 18% of fatal anaphylaxis cases were attributed to insect ingestion.[1]

Even in the Western world, we each unwittingly eat about half a kilogram of insect traces per year. In the United States, one might find edible whole insects sold as a novelty (eg, chocolate-covered ants). However, parts of insects or derivatives are commonplace in the North American diet.

For example, the red dye carmine is a product of the desiccated bodies of female cochineal insects. It may be found in many "red velvet" baked goods and surreptitiously in other foods. Allergic reactions to carmine dye have been reported in foods as varied as ruby-red grapefruit juice and dyed artificial crab.[2] It appears that the allergens may be cochineal insect proteins and not the purified dye itself. Identifying carmine in food ingredients may not be easy, because it may be listed as C.I. natural red no. 4 or as E120 in Europe.

Another hidden food allergen is the mite Dermatophagoides farinae, which may be found both in house dust and in stored wheat grain. A Venezuelan study of 30 patients who experienced systemic anaphylaxis after ingesting wheat-containing foods found that they were sensitive to dust mite but not wheat.[3] They also reported that mite contamination of wheat flour is common. Once a package of wheat flour is opened, the authors postulated, the mite population could proliferate depending on climatic conditions.

Analogous reactions to the lentil pest have been cited as a cause of anaphylaxis to insect-contaminated lentils.[4]

A few outbreaks of allergic reactions to insects have also been reported. In a thorough analysis of one such outbreak in Thailand, it was determined that the culprit allergen was not the insect, nor was it an allergen at all.[5] Instead, the cause was determined to be scombroid-like histamine poisoning of improperly stored grasshoppers and silkworm pupae. As with scombroid, the mechanism by which this occurs is that histidine in the grasshoppers and silkworm pupae is decarboxylated to histamine by bacteria. Because histamine is heat-stable, this toxin survives the cooking process and triggers reactions.

We can only guess as to how often insects are the hidden cause of a food allergy, but it is probably more frequent than we realize. Allergists often encounter unexplained reactions that are labeled idiopathic. Should we advise patients that it could have been insect contamination? Just a little food for thought.

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