Allergy trigger: Cannabis

Due to the worldwide progressing legalization of cannabidiol (CBO) and its increased use in various products, e.g. in the cosmetics industry, the number of people who are exposed to cannabis is growing. One thing that is still largely unknown is that even the oldest useful plant in the world can be an allergy trigger. Our medical team reports:

What is a cannabis allergy?

As with all allergies, a cannabis allergy is an overreaction of the immune system to a supposedly harmless substance - in this case to a component of the cannabis plant. In the case of first contact with cannabis through smoking joints or oral ingestion of cannabis products, the immune system may react by producing IgE antibodies in the blood - the patient is thus sensitized. If allergic symptoms occur with repeated contact, one speaks of a clinically manifest cannabis allergy.

Still few people are aware that the body can also react allergic to marijuana. A marijuana allergy is therefore seldom recognized or identified as the cause of various symptoms. But due to the progressive legalization of cannabidiol (CBO) within the EU and some American countries, such as Uruguay and some US states, larger and larger parts of the population are exposed to hemp. An increase in the number of people with a cannabis allergy is expected in the years to come, according to professional organisations like the American Academy of Allergy, Asthma & Immunology (AAAAI).

Trigger of a cannabis allergy

The exact allergy trigger of cannabis has already been identified. It is the protein Can s 3, which has been officially accepted by the IUIS (International Union of Immunological Societies) as an allergy trigger and used to test for cannabis allergy. Other plant constituents probably play a role as well, but need to be examined more closely.

Typical symptoms of a cannabis allergy

  • Red eyes
  • Swelling of the eyelids
  • Stuffy nose
  • Guttering nose
  • Swollen mucous membranes
  • Cough
  • Shortness of breath
  • Hives, skin rashes
  • Swelling of the skin
  • Anaphylactic shock

Two case reports

A Swiss research team presented the allergy course of two young patients at the European Allergy Congress EAACI 2020:

In the first case, the patient was surprised by her allergy after smoking a joint: she reported itchy, reddened, and swollen eyes, a runny nose and skin rashes, i.e. the severity of the reaction remained low.

The second patient, who had been known to suffer from asthma, had much more severe symptoms, equivalent to a grade III anaphylactic reaction. These were triggered by drinking a cannabis-containing almond milkshake. Skin rashes, shortness of breath, drowsiness, abdominal cramps, and diarrhoea were the consequences. Her symptoms were not only noticeable when smoking or by oral ingestion of hemp products in the gastrointestinal tract, but also when skin contact with the female plants of the cannabis was observed. The clinical picture of a cannabis allergy can therefore be very diverse - life-threatening conditions cannot be excluded. Especially the rapid intake of large amounts of cannabis via the consumption of hemp seeds or by drinking cannabis teas can be dangerous for those affected. Therefore, it is even more important to recognize a cannabis allergy in time.

Diagnosis of a cannabis allergy

To correctly test a cannabis allergy, it is suitable to perform tests in which the blood of the patient is examined for the presence of allergen specific IgE antibodies.

With igevia, the cannabis allergen Can s 3 is also determined for 285 allergens.

Cannabis and cross allergies

As with many pollen allergies, cannabis allergens are similar to those found in certain foods. The similarity is so great that the immune system cannot distinguish the proteins and a so-called cross-allergy is triggered. Patients therefore suffer from allergic symptoms not only after cannabis consumption but also after eating fruits and nuts.

The following 6 fruit/vegetable varieties are the most common cause of a cannabis cross-allergy:

  • Tomatoes
  • Peaches
  • Bananas
  • Apples
  • Cherries
  • Nuts

Cannabis allergy - what can affected persons do?

So far there is no form of therapy that can cure a cannabis allergy. A hyposensitization, i.e. an allergy vaccination, which is used e.g. for grass pollen, birch pollen or house dust mite allergy, does not exist yet.

The only way to protect yourself from allergic symptoms is to avoid the allergy trigger. Smoking (including passive smoking) of joints and the use of hemp products should be avoided. If severe anaphylactic reactions occur, an emergency doctor must be called immediately.


Majali Thomas ZR et al. Allergy to Cannabis sativa – two illustrative cases of an old drug with new relevance. EAACI 2020 Postersession

Armentia, A. et al. (2011). Allergic hypersensitivity to cannabis in patients with allergy and illicit drug users. Allergol Immunopathol, 39, 271-279.

Tessmer, A., et al. (2012) Hypersensitivity reactions to marijuana. Annals of Allergy, Asthma & Immunology, 108 (4), 282-284.  

Medically reviewed

This article has been examined for medical correctness by Nora Zulehner, PhD.

Posted by Magdalena Schirz on 8/5/2020

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