Marijuana Allergy? Legalization Stirs the Pot

Gary J. Stadtmauer, MD


October 02, 2019

Long before the effort to legalize marijuana gained traction, I saw a patient who was formerly a heavy marijuana pipe smoker. He was atopic but had no prior food allergies. He had smoked "many hundreds" of buds with the seeds but had had no experience with low-THC hemp until he ate hempseed-crusted catfish, whereupon he developed diffuse hives with dyspnea and dysphonia that responded to epinephrine and antihistamines.

Scratch testing with hempseed and IgE testing (by colleagues at the Mt. Sinai Jaffe Food Allergy Institute) were consistent with an allergic response. We published this first reported case[1] of an ingestion reaction to hempseed and wondered whether this was another case of inhalational sensitization leading to an ingestion reaction (as most commonly occurs with oral allergy syndrome).

Marijuana Across America

Fast-forward 16 years, and a lot has changed. For decades, all forms of cannabis had been illegal. Although hemp did not contain enough of the psychotropic THC—at less than 0.3%—to produce a "high," it was otherwise indistinguishable from marijuana, so it too was banned until 2000, when hempseed importation was permitted.

Last year, hemp cultivation was legalized by Congress, and the Drug Enforcement Administration recently clarified that hemp and its derivatives are legal. Meanwhile, medical marijuana is approved by most states, and the remaining ones have approved cannabinoid oil (without THC). In addition, a number of states have legalized marijuana for recreational use.

In Colorado, the first state to legalize recreational marijuana, both its use and reports of adverse health effects increased. It's easy to imagine how enticing a marijuana cookie, candy, or gummy bear could be to a child. It's not surprising, then, that legalization in Colorado was followed by an increase in calls to the poison control center for marijuana-related poisonings in children.

Cannabis and Hempseed Allergy Emerges

Since our first case, a plethora of patients have been reported to be allergic to both cannabis and hempseed.[2] Many had reactions to the first hempseed ingestion, and although most had previously used marijuana, some had not.

Personal use may not even be necessary to trigger hypersensitivity to hempseed or marijuana. Cases of secondhand cannabis smoke exposure triggering typical allergic respiratory symptoms—including rhinitis, conjunctivitis, and asthma symptoms—have been published.[3] It is also important to consider secondhand marijuana exposure in children with worsening asthma, as evidenced by one case.[4]

Why some marijuana users develop respiratory symptoms and others cutaneous is unclear, but it is probably a function of genetics and preexisting allergic diseases (asthma, eczema). Occupation exposure is another consideration in cannabis growers and handlers.

Marijuana use will probably increase even more over time, and with it, marijuana allergy. It was recently decriminalized in New York, and this NYC resident can definitely smell that change is in the air.

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