Written with Charles Cho
Food allergies are a rapidly growing medical and public health problem. Recent studies estimate an incidence of 5% in children younger than 5 years old and 4% in adults. In severe cases, subjects can experience anaphylaxis and even death if exposed to a food to which they are sensitive. There is no known cure. Rather, doctors recommend that the sufferer avoid exposure to the allergen. The mechanism of disease is thought to be immunologic.
A number of drugs can be used during an acute food allergy attack, but only one — intramuscular injection of epinephrine — immediately resolves all of the symptoms associated with the episode. Tellingly, epinephrine is a neurotransmitter/hormone of the autonomic nervous system (ANS) that augments sympathetic function. Emerging data in the literature supports a neuro-immune connection, particularly in light of how the ANS innervates and regulates lymphoid tissues and other constituents of the immune system. It is possible that food allergy syndrome (and perhaps all cases of anaphylaxis) may require both an allergic sensitivity and an underlying inability to generate an adequate sympathetic response (or an underlying parasympathetic/ vagal dominance).1
Ethylene is a gaseous hydrocarbon with the molecular structure C2H4. It is commonly produced when hydrocarbons are exposed to oxidative stress, such as that found during lightning, volcanic eruptions, forest fires, and photochemical reactions on the ocean surface. Plants coopted ethylene biosynthesis during evolution to manage their response to oxidative stress from biotic and abiotic sources. Further exaptations of ethylene include modulation of plant life history events such as development, transformation, senescence, and death.
Due to a number of factors described below, humans may be subject to increasing ethylene exposure. The potential health consequences of ethylene exposure are not part of the public consciousness and warrant further exploration.