SAN FRANCISCO – Marijuana hypersensitivity might be more common than previously thought, according to the results of a case series.
Though there are only a few case reports in the literature, "Marijuana allergy, I think, is fairly common," said lead investigator Dr. Gordon Sussman, acting division director of clinical allergy and immunology at the University of Toronto. Even so, "It’s something physicians don’t really generally ask about. People should consider it in the diagnosis of rhinitis [and other allergic symptoms], and even in people that have asthma and anaphylaxis."
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Dr. Gordon Sussman says allergic reactions to marijuana shouldn't be a surprise because it is a weed, and weeds are generally known to be allergenic.
The 17 patients who were included in the series reported that marijuana gave them runny noses or other problems; all ended up having positive marijuana skin prick test results, he reported. One patient in the series had an anaphylactic reaction after drinking marijuana tea.
That was the first patient in whom Dr. Sussman diagnosed a marijuana allergy. "I asked him in a detailed history what it could have been, and he actually had drunk marijuana tea. We knew at that point he had an IgE-mediated reaction to marijuana," he said.
Curiosity piqued, and Dr. Sussman began asking allergy patients about marijuana use and reactions. A significant percentage reported symptoms from both contact and inhalation.
To confirm the diagnosis, he and his colleagues did skin-prick tests on the 17 patients between 21 and 58 years old, mostly men. They extracted buds or flowers in 5 mL of water for 15 minutes and pricked beneath drops placed on patients’ skin.
After 15 minutes, the 17 patients had wheals of 4-19 mm and surrounding flares. Fifteen presented with inhalation symptoms, including rhinitis and conjunctivitis, periorbital angioedema, wheezing, sinusitis, and throat swelling. Thirteen also reported hives from contact.
The anaphylaxis patient presented with anxiety, chest tightness, wheezing, GI cramping, and vomiting after drinking the tea.
"I don’t think it’s a contaminant; I’m pretty sure it’s an allergen in the marijuana they are reacting to," Dr. Sussman said, adding that such reactions shouldn’t be a surprise because "marijuana is a weed, and weeds are generally known to be allergenic."
Asking about marijuana use and past reactions should be a routine part of allergy work-ups, especially with expanding medical marijuana use. "People could actually be sensitized to marijuana and have a serious reaction. It’s important for people to recognize this," Dr. Sussman said.
The researchers’ next step is to identify the actual allergens responsible for the reactions using a marijuana extract from a U.S. federal laboratory, serum from positive patients, and Western blot assays.
There was no outside funding for the study. Dr. Sussman said he had no disclosures.