As cannabis becomes more common and less taboo, veteran and novice consumers alike are becoming more aware of the way human bodies react to the plant. Those who experience seasonal, plant, or food allergies may wonder if it's possible to be allergic to cannabis and what the signs and symptoms of a cannabis allergy might be.
Cannabis allergies: what we know so far
Though the research thus far is limited, we do know that cannabis allergies exist. Cannabis has a long, storied history of both stigma and mystique, with a wide range of effects and side effects that have been attributed to the plant over the years. Some effects attributed to cannabis have been accurate, others completely fabricated.
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If LTPs aren't the only source of cannabis allergies, what other factors are at play? You've probably heard a lot about terpenes lately
But the possibility of cannabis allergy is neither an overblown anti-marijuana scare tactic nor an indication that the plant is less healthful or therapeutic than we thought. Rather, it is the same as any other typically beneficial plant that may cause allergies in some people.
So let's look at the available research to better understand the mechanisms that cause allergic reactions in some cannabis consumers.
Lipid transfer proteins
Several recent studies have identified lipid transfer proteins (LTPs) as probable allergens in cannabis. LTPs are often found in plant-based foods and pollen. They cause allergic reactions in humans by triggering an overproduction of antibodies.
In a March 2019 study published in The Journal of Allergy & Clinical Immunology: In Practice, 120 cannabis allergy patients and 62 healthy control subjects were given a hemp extract through three different administration tests, including a skin-prick test. The hemp extract was rich in an LTP prevalent in cannabis. The study concluded that about 80% of cannabis allergy patients tested were sensitive to the protein.
In short, this study suggests that LTPs aren't the only cannabis allergen, but play a prominent role in triggering allergic reactions to cannabis.
Cross-Reactivity
Other studies have shown similar results when testing cannabis LTP sensitivity among cannabis allergy patients. Some of these studies also show a recurring cross-reactivity to other plants that contain similar proteins, according to a December 2017 study published in the French Journal of Clinical Pneumology. Cross-reactivity occurs when someone has an allergic reaction to similar proteins from different substances. About 45% of cannabis allergic patients in the Journal of Allergy & Clinical Immunology study also reported allergic reactions to plant-derived foods.
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A 2013 study from the journal Internal Archives of Allergy and Immunology tested 21 patients with food allergies for reactivity to cannabis LTPs. Twelve of the 21 test subjects were also allergic to cannabis, and all 12 had more severe reactions to their food triggers than those without a cannabis allergy.
A 2008 study from the same journal tested 32 subjects for an allergic reaction to cannabis LTPs, as well as tomato, peach peel, and pollen extracts. All subjects sensitive to tomato allergens were also sensitive to cannabis. Cross-reactivity to peach peel and cannabis was also prominent.
These studies provide further evidence that LTPs play a central role in cannabis allergies, and may be the main culprit of cross-reactivity with other food allergies.
Terpenes
LTPs aren't the only source of cannabis allergies, other factors are at play as well. You've probably heard a lot about terpenes lately — the compounds responsible for the aroma and flavor of cannabis and a variety of other plants. Similar to prominent cannabis compounds like cannabidiol (CBD) and tetrahydrocannabinol (THC), terpenes have a wide variety of purported medicinal benefits. They may also be responsible, at least partially, for allergic reactions to cannabis in some users.
The terpene linalool, for example, has been found to elicit allergic reactions when oxidized, or exposed to the air. A 2010 study of linalool placed varying concentrations of oxidized linalool patches on the skin of 1,151 dermatitis patients, with 5 to 7% of patients testing positive for linalool sensitivity. A similar study from 2016 tested oxidized linalool and oxidized limonene, another prominent terpene in cannabis, on a group of 2,900 dermatitis patients, and found that 281 of them had allergic reactions to one or both of the terpenes.
Findings like these don't necessarily point to a high chance that terpenes are a prominent contributor to most cannabis allergies, but they do present a definite possibility that some allergic reactions to cannabis, especially skin allergies, are terpene-related.
Signs and symptoms of a cannabis allergy
Depending on the route through which it reacts with the body — i.e. skin contact, inhalation of pollen, etc. — cannabis is reported to produce a wide variety of allergy symptoms, most of which are typical of other allergies.
In a report from Canada's CTV News on the emerging trend of cannabis allergies in the post-legalization era, Toronto-based immunologist and allergy expert Dr. Gordon Sussman said that more exposure to marijuana among the general public will inevitably lead to more reported cases of cannabis allergies.
Sussman has seen a rising number of cannabis-sensitive patients over the past ten years and is actively studying undiagnosed cannabis allergies to raise awareness and better prepare physicians.
“If you look at a study done out of Colorado, about 10% of people just with passive exposure did have [cannabis] allergy symptoms,” Dr. Sussman said. In the same CTV report, Dr. Sussman said that skin contact with the cannabis plant can cause irritation ranging from a mild itch to hives and puffy eyes. Smoking cannabis or inhaling cannabis pollen can lead to sneezing and a runny nose as well as wheezing, shortness of breath, and asthma symptoms. When cannabis patients eat hemp seed or other cannabis products, it's also possible to experience anaphylactic symptoms.
What to do if you're allergic to cannabis
Sussman told CTV News that simply avoiding marijuana is the only “truly effective way to deal with a marijuana allergy.” The good news is, if you test positive for cannabis allergies and experience common allergy symptoms, a doctor or allergy specialist may be able to prescribe common allergy treatments — i.e., nasal spray, antihistamines, or EpiPens, if necessary — to reduce or eliminate symptoms.
Major contributions from Dr. Adie Rae.
