Cannabis Allergies: What Do We Know?

Alternaleaf Team
Written by
Alternaleaf Team
Aug 25, 2023
Last updated:
Dec 15, 2023

Cannabis allergies are rare, but they do exist. The widespread legalisation of medical cannabis means that more and more people are exposed to it, causing an increased interest in cannabis allergies and the risks they may pose.

As a pollinating plant, the workforce involved in growing and handling medical cannabis plants are particularly at risk of allergic reactions. However, medical cannabis patients also need to know about cannabis allergy symptoms, how to treat them and the parts of cannabis that can cause allergies.

What Are The Symptoms Of Cannabis Allergy?

The symptoms of a cannabis allergy are usually mild, but they can on occasion be serious. Usually, someone with a cannabis allergy will experience rhinitis (inflammation of the mucous membranes inside the nose), an itchy throat and watering eyes. Medical cannabis may also trigger asthma in some patients, but the research around this is inconclusive.

In more serious cannabis allergy cases, someone might experience lower respiratory symptoms including coughing, shortness of breath and chest tightness. People have also reported skin irritation such as hives, swelling and eczema flares.

Any method of medical cannabis consumption can trigger allergy symptoms, including ingestion, topical application and direct or second-hand inhalation. Directly touching the cannabis plant can also cause an allergic reaction.

Medical cannabis may also worsen or improve allergic asthma symptoms depending on how it’s consumed. Smoking or vaping cannabis can irritate the airways and cause coughing, potentially leading to asthma attacks. However, some research suggests medical cannabis may be a bronchodilator, meaning it relaxes the airways and improves breathing. No conclusive evidence suggests that medical cannabis is an effective treatment for asthma, however.  

What Causes Cannabis Allergy?

Allergic reactions are essentially the immune system overreacting to a perceived threat. The sneezing, runny nose, itching and other symptoms commonly experienced with allergies are caused by the release of antibodies that are trying to clear the allergen from your system.

Cannabis is an airborne allergen, meaning it releases buoyant pollen grains that can travel for many miles. Similar to other plant pollen, cannabis pollen can trigger hay fever. Only male cannabis plants produce pollen, however, and most medical cannabis products are made with female plants, meaning they shouldn't contain pollen. This means that any reaction you might have to pollen in medical cannabis is likely due to cross-contamination.

Some people may also be allergic to certain terpenes found in medical cannabis such as linalool, but the evidence for this is limited. Terpenes typically need to be exposed to air (oxidised) to become allergenic. This means that some cannabis consumption methods such as oils and topical creams might not cause the oxidation necessary to transform terpenes into allergens.

There are also cross-reactive allergies – some foods and substances share similar protein properties to cannabis, including peaches, tomatoes, grapefruit, almonds and chestnuts. If you’re allergic to one of these foods, you may experience a cross-reactive allergic reaction to medical cannabis.

One review also suggested that THC may be a direct allergen for some people, although the evidence is inconclusive.

How Does a Doctor Diagnose A Cannabis Allergy?

If you suspect you may be allergic to medical cannabis, there are some tests you can take to find out. The most common methods a doctor will use to determine if you're allergic to cannabis is a skin prick test or a blood test.

If you see a doctor about a suspected cannabis allergy, they will first assess your medical history, and then perform a physical examination. The doctor might then use a skin prick test. A skin prick test is non-invasive, and involves applying an allergen to your skin’s surface with a needle and waiting to see if any irritation occurs.

If any redness, swelling or itching occurs within 15 minutes, it may mean that you’re allergic to that allergen. A doctor might also use an intradermal test, which involves injecting an allergen slightly below the skin with a needle.

Blood tests are another way doctors can determine whether you’re allergic to a specific allergen such as cannabis. Antibodies are proteins that are released when we encounter a possible allergen – when doctors perform a blood test on a patient who thinks they might have a cannabis allergy, they test for specific types of antibodies as a reaction to cannabis. If you have more of these antibodies in your blood than usual after being exposed to cannabis, you’re probably allergic to it.

Can I Grow Out of a Cannabis Allergy?

While some allergies may improve with age, we don’t yet know whether it’s possible to outgrow a cannabis allergy. The immune system can become less reactive to certain allergens over time, but whether this applies to allergens in cannabis such as certain terpenes and proteins isn’t known. Most allergies typically require long-term treatment or avoidance of the allergen.

How Can I Manage a Cannabis Allergy?

Cannabis allergies can be difficult if you use medical cannabis to manage another condition. If your cannabis allergy is severe, avoiding medical cannabis is the best option. If your allergy symptoms are mild, you may find some relief with certain medications such as antihistamines and decongestants. You may also want to carry your inhaler if you’re using medical cannabis and have a history of asthma or respiratory problems.

If you suspect you might be allergic to medical cannabis, there are tests your doctor can perform to make sure. Once you know what is causing an allergic reaction, your doctor can help you decide how to move forward. Thankfully, medical cannabis allergies are rare and usually mild. Staying on top of your health is key and whenever you have an adverse reaction to any medication make sure to see your doctor as soon as possible.

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