Hemp seed can cause allergic reactions, including rare cases of anaphylaxis. This page is general information, not a diagnosis: anyone who has reacted to hemp, or who has nut, seed or cannabis allergies, should talk to a doctor or allergist.
Are hemp seeds an allergen?
Yes. Hemp seed can cause a true food allergy, and anaphylaxis after eating hemp seed was described in a medical journal as early as 2003. It is not a common allergen, and it is not on Canada's list of priority food allergens.
Every food made from the seed contains the same proteins: hemp hearts (hulled hemp seeds), hemp milk, hemp protein powder and hemp flour. If you react to one, avoid the others as well until an allergist tells you otherwise.
The people with the most reason to check with an allergist before eating hemp are those who have reacted to cannabis smoke, pollen or plants, those with a lipid transfer protein allergy (often to peach), and those with a hazelnut or other nut or seed allergy. The sections below explain why.
How common is hemp seed allergy?
No reliable figure exists. The medical literature on hemp seed allergy is mostly individual case reports and small case series. Reviews of cannabis allergy in general describe its true prevalence as unknown and probably underestimated, because many clinicians are not familiar with it.
Canadian data are thin too. In a Canadian survey published in 2021 (run in 2019 and 2020), allergists reviewed reports from the parents of 68 children who had reacted to foods outside the priority allergen list. One reaction involved hemp seed. Green peas were named for 13 children and coconut for 7.
What are the symptoms of a hemp seed allergy?
Symptoms of a hemp seed allergy can include hives, swelling of the face, lips or tongue, coughing or wheezing, a hoarse voice, and nausea or vomiting. A severe reaction (anaphylaxis) can affect breathing and circulation and can be life-threatening. The signs are the same as for any food allergy. Health Canada's list of signs of an allergic reaction includes:
- Skin: hives, swelling of the face, lips or tongue, itching, warmth, redness
- Breathing: coughing, wheezing, shortness of breath, chest pain or tightness, throat tightness, hoarse voice, trouble swallowing, nasal congestion or hay-fever-like symptoms
- Stomach and gut: nausea, pain or cramps, vomiting, diarrhea
- Heart and circulation: paler than normal or blue skin colour, weak pulse, dizziness or light-headedness, loss of consciousness, shock
- Other: anxiety, a sense of impending doom, headache, uterine cramps, metallic taste
Reported hemp seed cases describe hives, facial swelling, breathing difficulty and a hoarse voice, starting anywhere from a few minutes to about an hour after eating. A severe reaction (anaphylaxis) is a medical emergency. Use an epinephrine auto-injector if one has been prescribed, then call 911 (or your local emergency number) so you can be taken to hospital. Health Canada notes that epinephrine is the only medication that can stop an allergic reaction from progressing, and that hospital treatment and observation are still needed after it is given.
A rash where hemp seed oil has touched the skin is a different kind of reaction, covered in the hemp seed oil section below.
Which proteins in hemp seed cause allergic reactions?
Researchers do not yet know for certain. The main storage protein in hemp seed is edestin, an 11S globulin that makes up roughly 60 to 80 percent of the seed's protein. The rest is mainly 2S albumins and 7S vicilin-like proteins, in proportions that vary between studies. (For the nutrition side, see edestin and hemp's other proteins.)
A 2023 French laboratory study tested hemp seed extracts against blood serum from people sensitized to hemp seed or to other seeds and nuts. It identified edestins and vicilins as potential hemp seed allergens, and its authors note that the major hemp seed allergens have not yet been identified. None of the cannabis allergens registered in the WHO/IUIS allergen nomenclature database is a seed storage protein. The five listed (Can s 2, 3, 4, 5 and 7) are all classed as airway allergens.
Does hemp seed cross-react with other foods?
Possibly, but the evidence is limited. Two separate mechanisms are often blurred together.
Seed storage proteins and hazelnut
Edestin belongs to the same protein family (11S globulins) as known allergens in peanut, hazelnut and sesame (Ara h 3, Cor a 9 and Ses i 6). Two proteins being in the same family does not by itself mean a person will react to both. In the 2023 study, hemp seed proteins blocked about 25 to 30 percent of IgE binding to hazelnut in serum from hazelnut-sensitized people, which points to possible cross-reactivity with hazelnut. The authors say its clinical relevance still has to be tested in people who are allergic to hazelnut.
Lipid transfer protein: peach, tomato and the cannabis plant
Can s 3 is a lipid transfer protein (LTP) and the best-studied cannabis allergen. People sensitized to it, usually through smoking cannabis, breathing second-hand smoke or exposure to the pollen, have reacted to tomato, peach and other fruits of the rose family, hazelnut, walnut, peanut, kiwi, banana, citrus fruits and grapes. This pattern is called cannabis-fruit/vegetable syndrome. Reactions to these foods in people sensitized to cannabis have so far been reported only in Europe, and studies from the United States have not found Can s 3 to be a relevant allergen in people with cannabis allergy. Its importance in Canada is not known.
The evidence linking this to hemp seed is narrower. A 2024 Italian case series describes anaphylaxis after a cake made with hemp flour in a woman who was sensitized to Can s 3 and had smoked cannabis before. The authors suspected that earlier cannabis exposure was the starting point. A positive LTP test is not the same as an allergy: people sensitized to one LTP often test positive to others without reacting to those foods. There is no general rule for whether someone with a peach or tomato allergy will react to hemp seed. An allergist has to assess each case.
Are hemp seeds tree nuts?
No. Hemp seed is not a tree nut. The hemp plant, Cannabis sativa, is an annual herb in the Cannabaceae family, not a tree. Botanically, what is sold as hemp seed is an achene: a small, dry, one-seeded fruit that does not split open. The nuts named in the food allergen definition in Canada's Food and Drug Regulations are almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pine nuts, pistachios and walnuts. Hemp is not among them.
That does not settle whether someone with a tree nut allergy can eat hemp safely. The possible overlap with hazelnut described above, and the chance that a hemp product was processed near nuts, are both reasons to ask an allergist first.
Is hemp seed allergy the same as cannabis allergy?
No, but the two overlap. Cannabis allergy usually means a reaction to the plant itself: its pollen, smoke, leaves or flowers. The most common symptoms are hay-fever-type symptoms (runny nose, itchy or watery eyes) and hives or swelling where the plant touches the skin, though severe reactions also occur. People living near hemp fields can get hay-fever-type symptoms from hemp pollen.
Hemp seed allergy is a food allergy to the seed. A case series from Montreal found that most people who reacted to hemp seed were cannabis users. But 27 percent were not, which suggests hemp seed allergy can also develop in people who do not use cannabis. Cannabis allergy has been reported more often over the past decade as cultivation has grown and legal status has changed. If you have a known cannabis allergy, talk to your allergist before eating hemp foods.
Can hemp seed oil cause an allergic reaction?
It can, although less is known about it. Hemp seed oil is almost entirely fat, but cold-pressed oils are not protein-free. A 2020 study of cold-pressed oils found protein fragments specific to hemp in hemp seed oil. Allergic contact dermatitis from hemp seed oil applied to the skin has also been reported. Anyone with a confirmed hemp seed allergy should ask their allergist before using hemp seed oil in food or on the skin.
Is hemp a priority allergen in Canada?
No. Hemp is not on Health Canada's list of priority food allergens, and the Food and Drug Regulations do not include it in their definition of a food allergen. The priority list covers eggs, milk, mustard, peanuts, crustaceans and molluscs, fish, sesame seeds, soy, sulphites, tree nuts, and wheat and triticale.
This affects labelling. When a priority allergen or a gluten source is in a prepackaged food, its source must be shown in the list of ingredients or in a "Contains" statement. Hemp gets no such flag. Hemp seed, hemp flour or hemp protein added to a prepackaged food with more than one ingredient is generally named in the list of ingredients. Hemp seed oil used as an ingredient in another food may be listed only as "vegetable oil", though. Some foods need no ingredient list at all, such as foods packaged from bulk in the store where they are sold. Precautionary "may contain" statements are voluntary. If you avoid hemp, read the ingredient list every time, and contact the manufacturer when a label says "vegetable oil" or is unclear.
When deciding whether to add a food to the priority list, Health Canada has used three criteria: a credible cause-and-effect link, reports of severe systemic reactions, and prevalence data from Canada or elsewhere. Hemp has not been added.
What should you do if you think you are allergic to hemp seed?
- If symptoms are severe (trouble breathing, throat tightness, swelling of the tongue, feeling faint), use an epinephrine auto-injector if you have one and call 911.
- Stop eating hemp foods until you have seen a doctor. That includes hemp hearts, hemp milk, hemp protein powder and anything with hemp in its ingredient list.
- Write down what you ate and how much, the product name and ingredient list, when the symptoms started and what they were.
- Ask your doctor about a referral to an allergist. Do not test yourself by eating hemp again to see what happens.
Testing for hemp and cannabis allergy is not standardized. There are no commercial skin-test extracts for cannabis, and blood tests can be positive in people who tolerate it. An allergist has to read the results alongside your history. If you have had a severe reaction, your allergist may prescribe an epinephrine auto-injector and give you an emergency plan.
If your child already has food allergies, ask their doctor or allergist before offering hemp. For babies who are just starting solids, see this guide to shelled hemp seed for babies and toddlers.