As cannabis becomes more common and less taboo, veteran and novice users alike are becoming more aware of the way human bodies react to the plant. If you experience seasonal, plant, or food allergies, you might be asking yourself, “Could I be allergic to cannabis?”
And if a cannabis allergy exists, what types of signs and symptoms should you look out for?
Cannabis allergies: what we know so far
Though the research thus far is limited, we do know that allergies and reactions to cannabis occur. 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, while others are completely fabricated.
But the possibility of cannabis allergies is neither an overblown anti-cannabis scare tactic nor an indication that the plant is less healthful or therapeutic than we thought. Rather, it is the same as any other plant which, though typically beneficial, may cause allergies in some consumers.
So let's look at the available research to better understand the mechanisms that cause allergic reactions in some cannabis users.
Studies have shown similar results when testing cannabis Lipid Transfer Protein (LPT)-sensitivity among cannabis-allergic 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. According to a study in the Journal of Allergy & Clinical Immunology, about 45% of patients who were allergic to cannabis also reported a reaction to plant-derived foods.
A 2013 study from the 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 twelve had more severe reactions to food than those without a cannabis allergy. A 2008 study from the same journal tested 32 subjects for any 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 a factor in cross-reactivity with other allergies.
Lipid transfer proteins (LTPs)
Several recent studies have identified lipid transfer proteins (LTPs) as probable allergens in cannabis. LTPs are proteins that act as allergens, often found in plant-based foods and — in this case — the cannabis plant. LTPs 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 Can s 3, a non-specific LTP (ns-LTP) prevalent in cannabis. The study concluded that about 80% of patients with cannabis allergies tested were sensitive to the Can s 3 protein, with 72% of anaphylactic patients also testing positive for Can s 3 sensitivity.
In short, this study suggests that LTPs aren't the only cannabis allergen, but they play a prominent role for individuals experiencing allergic reactions to cannabis.
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 — the compounds responsible for the aroma and flavor of cannabis sativa and a variety of other plants. Similar to prominent cannabis compounds like cannabidiol (CBD) and THC, terpenes have a wide variety of medicinal benefits. They may also be responsible, at least partially, for unwanted allergies to cannabis in some users.
The terpene linalool, for example, has been found to elicit an allergic reaction 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 5-7% of patients testing positive for linalool sensitivity. A similar study from 2016 tested oxidized linalool and oxidized limonene, another prominent terpene in cannabis sativa, on a group of 2,900 dermatitis patients, and found that 281 of them had allergic reactions following exposure 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 marijuana allergies, but they do present a definite possibility that some allergic reactions to marijuana, 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. — allergies to the marijuana plant are reported to produce a wide variety of 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 10 years, and is actively studying the phenomenon of undiagnosed cannabis allergies to raise awareness and better prepare physicians.
“If you look at a study done out of Colorado, about 10 percent 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 marijuana pollen can lead to sneezing and a runny nose as well as wheezing, shortness of breath, and asthma symptoms. When marijuana patients eat hempseed or other cannabis products, it's also possible to experience anaphylactic symptoms.
It is also possible to have an allergy to the pollen found in hemp. One study out of Nebraska found up to 35% of the pollen in the area was from hemp and several patients experienced symptoms of rhinitis when exposed to cannabis in the summer months.
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 treatment methods — i.e. nasal spray, antihistamines, or EpiPens if necessary — to reduce or eliminate symptoms.