In recent years, 19 U.S. states and Canada have legalized cannabis, aka marijuana, for recreational use, while 38 states have okayed it for medical use. But as legalization has spread, so have reports of allergic reactions to marijuana.
In those with a marijuana allergy, experts say there is a range of possible reactions.
Reaction types include:
- Inhaling the marijuana plant’s pollen may trigger rhinitis, with sneezing and congestion, or eye allergy symptoms.
- In those with asthma, inhaled allergen exposure may cause coughing, shortness of breath and wheezing.
- Handling plants may cause hives and skin swelling for some.
- In rare cases, the consumption of certain cannabis products may lead to anaphylaxis.
- As well, marijuana can be a “co-factor” as opposed to an allergen per se. In such cases, it will worsen reactions to food or other allergens.
Marijuana, which is cultivated from the Cannabis sativa plant, is the most widely used recreational drug in the world. In 2019, about 18 percent of Americans had used it at least once that year. That number was even higher among teens: 22 percent of U.S. teens reported using marijuana in the past 30 days.
There aren’t yet good statistics on how common marijuana allergy is. But people with environmental allergies to grasses, trees or ragweed pollen are the most likely to react to cannabis, says Dr. Samira Jeimy, program director for clinical immunology and allergy at Western University in Ontario, Canada.
The allergist has long asked her teen and adult patients about their use of alcohol or tobacco, both of which can impact allergies. Today, she also asks about marijuana.
All About Marijuana Allergy
To learn more about marijuana allergy reactions and everything from sensitization to vaping, hemp seeds and CBD edibles, Allergic Living gets insights on key points from three allergist experts. We interview Jeimy, Dr. Hannelore Brucker, an allergist-immunologist in Minneapolis, Minnesota, and Dr. Gordon Sussman, professor of medicine at the University of Toronto. All are members of the International Cannabis Allergy Collaboration, a group researching marijuana allergies.
What Causes Reactions
The cannabis plant contains more than 100 compounds, called cannabinoids. Two get most of the attention: tetrahydrocannabinol (THC), which is used for its euphoric and relaxing effects, and cannabidiol (CBD), which doesn’t cause a “high” but may also help with relaxation and anxiety-reduction.
Yet neither THC nor CBD contains protein, and therefore they aren’t the cause of IgE-mediated allergic reactions, Jeimy explains. It is proteins found in the leaves, buds, flowers and seeds of the plant that trigger allergic reactions to cannabis. Several allergens have been identified, but the major one is Can s 3.
How Sensitization Happens
You can become sensitized to Can s 3 by handling marijuana plants, smoking marijuana joints, or by consuming products containing the Cannabis sativa plant, says Jeimy. This includes eating hemp seeds, which are from the Cannabis sativa plant but contain only trace amounts of THC and do not produce a high. She says there are even some cases of sensitization occurring through second-hand marijuana smoke.
Edibles and Gummies
Edibles are food products infused with the marijuana plant, or the cannabinoids THC or CBD. There are different forms of edibles, from brownies to gummies and more.
If the edible contains the marijuana leaves or buds, eating it could cause an allergic reaction. However, “pot” gummies may contain only the protein-free THC, and are unlikely to cause an allergic reaction, Jeimy says. Same for CBD gummies and products made with the plant’s resin (such as hashish oil), which doesn’t contain Can s 3.
Yet, Brucker recommends caution with edibles. The U.S. Food and Drug Administration (FDA) doesn’t require the makers of cannabis products to provide consumers with information about ingredients. So consumers cannot be sure whether a product contains enough Can s 3 or other allergens to cause an allergic reaction. (However, a few states where marijuana is legal have passed their own laws on labeling requirements.)
Marijuana Allergy Symptoms & Anaphylaxis
The most common symptoms of marijuana allergy are mild and include a runny nose, sneezing and itchy eyes, Sussman says. Respiratory symptoms, such as wheezing or cough, and contact urticaria, or hives, from touching cannabis also occur.
Anaphylaxis is rare from smoking or vaping pot – to have that significant of a reaction, you usually need to consume it, he says. “We had a patient who reacted to a tea made with cannabis. He had chest tightness, wheezing, abdominal cramps and vomiting. It was a pretty significant reaction.”
Another potential source of anaphylaxis: Eating hemp seeds, which may be added to health foods, baked goods and smoothies.
Testing and Diagnosing
Marijuana allergy is diagnosed through patient history, and skin testing. To do this, allergists make extracts from the buds and leaves. There is no cannabis extract available for use in routine allergy testing. What allergists make is “a pretty crude extract. We need better diagnostic tests,” Sussman says.
It’s not just the cannabis allergy testing that’s lacking. Because cannabis isn’t legal at the U.S. federal level, research into marijuana allergy has been held back by stigma and a lack of funding, says Brucker. Her group, the International Cannabis Allergy Collaboration, is trying to change that.
Cannabis and Cross-Reactions
The Can s 3 protein can cross-react with proteins in various fruits, vegetables, nuts, latex, and tobacco. People who develop a cannabis allergy may also become sensitized to those other foods, leading to new IgE-based allergies, Brucker says.
Marijuana allergy may also trigger oral allergy syndrome (OAS), also known as pollen-food syndrome. In OAS, people who have environmental allergies to pollen, often birch or alder tree, may also get symptoms when they eat certain raw fruits and vegetables. The same is true for the Cannabis sativa pollen.
To the immune system, the proteins of the pollen and foods such as cherry, tangerine, peach, tomato, hazelnut or sometimes latex and tobacco, look similar.
OAS symptoms are typically mild, usually an itchy, tingling mouth when eaten in the raw form. “Very rarely it does result in anaphylaxis, though,” Jeimy says.
In assessing whether a person has common OAS reactions or might be at risk of more serious reactions, Jeimy asks patients if they have reacted to raw or cooked forms of fruits or vegetables. Heat from cooking usually changes the shape of these food proteins. When that occurs, the immune system no longer reacts to the proteins like a pollen. This is why people with OAS often can eat baked or boiled forms of the fruits and vegetables without a problem.
But the proteins that have the potential to cause more serious reactions are heat-resistant. Cooking won’t change their shape. So a prior reaction to a cooked form of a fruit or vegetable is more likely to indicate anaphylaxis risk, Jeimy says.
If someone has mild allergy symptoms when smoking marijuana or touching the leaves or buds, they should avoid eating hemp seeds, the allergist says. Likewise, people with allergies to stone fruits (like peach or cherry) or tree nuts should be aware of the potential for cross-reactivity with marijuana or hemp seeds.
Marijuana & ‘Co-Factor’ Reactions
Another special concern for people with allergies: research suggests cannabis has the potential to make an allergic reaction to a food more severe.
Like exercise, alcohol and non-steroidal anti-inflammatory drugs (or NSAIDs, such as aspirin and ibuprofen), cannabis may contribute to “co-factor-mediated reactions.” That is, it may lower the reaction threshold or increase a mild reaction into anaphylaxis.
“When patients have experienced anaphylaxis, we ask them about those co-factors. We always ask about cannabis, too. These are all things that can increase your possibility of having anaphylaxis,” says Jeimy.
One theory is that, similar to the effects of alcohol, cannabis relaxes the arteries (called vasodilation) which may allow more allergenic proteins to be absorbed into the bloodstream through the gut, Jeimy says. Another theory is cannabis, like viral illnesses, may make certain immune system cells more reactive.
Asthma and Cannabis Concerns
THC is a bronchodilator, meaning it relaxes the muscles in the airways, and may have anti-inflammatory effects in the lungs, research suggests. Because of this, cannabis has been tried as an asthma treatment. (There are cannabinoid inhalers for sale for medical use.)
But allergists don’t recommend it. The bronchodilator effects last only a few hours, Brucker says, while chronic cannabis users are more likely to have respiratory symptoms such as cough, mucus production, and chest tightness.
“The major issue is with smoking,” says Jeimy. “The cannabis particles can become volatile particles, that can be an irritant if you are inhaling it deep into the lungs, even in the absence of having a cannabis allergy.”
Breathing in marijuana smoke over the long-term may also sensitize kids. Such exposure also worsens children’s asthma symptoms.
Other Lung Effects
There have also been case reports of cannabis contaminated with mold spores causing Aspergillosis, a serious lung infection. “If you use organic material like leaves, you crush it and you smoke it, there can be fungus in those leaves,” Brucker says.
Teens who vape cannabis extracts, including THC oils (known as dabbing), are also twice as likely to report “wheezing or whistling in their chest,” than those who don’t, found a survey of nearly 15,000 kids ages 12 to 17. Vaping is thought to injure adolescent lungs, according to University of Michigan researchers.
Marijuana Allergy Take-home Messages
Be candid about this drug with your allergist. And allergists should routinely ask about marijuana use. “With legalization, there is increased recognition,” says Sussman.
Jeimy says that when treating patients, “coming to it from a place of no judgment is helpful. Cannabis is legal in a lot of states and we’re not here to police people’s habits and behaviors. When we ask about smoking, people think we mean cigarettes, so it’s important to specifically ask about cannabis.”