Can You Be Allergic to Weed? Symptoms and Triggers

Yes, you can be allergic to weed. A cannabis allergy can cause itchy, watery eyes, a runny nose, coughing, wheezing, skin rashes or hives, and it can show up after smoking, eating edibles, touching the plant or breathing in its pollen. A little cough or reaching for eye drops mid-session is normal; worrying physical symptoms may mean an allergic reaction.

Cannabis allergy is underdiagnosed, and it can hit even seasoned smokers who never had a problem before. In principle it may get more common as weed gets easier to access, since more people are exposed to the plant and its pollen.

So can you actually test for a cannabis allergy? Here's what we know.

How do I know if I'm allergic to weed?

Symptoms of a weed allergy can show up in different ways depending on how you were exposed. If you touched the plant, you might break out in skin rashes, hives or swelling known as angioedema.

If you breathe in cannabis allergens, you might get nose or eye allergy symptoms: runny nose, sneezing, itching, swelling and watery eyes. Asthma symptoms can show up too, with wheezing and shortness of breath.

What are the symptoms of a cannabis allergy?

Cannabis allergy symptoms can kick in around 20 to 30 minutes after exposure. Here are some of the signs to watch for:

• Red, itchy or watery eyes (the most common sign)
• Rhinitis, runny nose or sneezing
• Stuffy nose
• Postnasal drip
• Wet cough
• Trouble breathing
• Sore or itchy throat
• Stomach cramps
• Nausea and vomiting
• Itchy skin
• Rashes or swelling under the skin

Keep in mind these symptoms vary from person to person, depending on how and how often you came into contact with cannabis and how much you used. If you feel off after smoking or being around pollen, you may get symptoms a lot like seasonal allergies. If you're allergic and eat edibles, you could get stomach trouble or skin rashes, and the same goes for handling the plant.

What triggers a cannabis plant allergy?

Allergic reactions to cannabis can look a lot like seasonal allergies or food intolerances. They can also be triggered by:

• Smoking or handling dried flower, resin or oils
• Taking CBD oil
• Eating cannabis edibles
• Airborne pollen or mold
• Handling dried flower, resin or oils followed by UV light exposure (phytophotodermatitis)

It's worth knowing these symptoms, because a cannabis allergy can show up in different ways, and it can even affect people who've used for years and were never allergic to anything.

Whether you develop a weed allergy depends on several factors, including how much cannabis you use, whether you already have other allergies and how close you live to cannabis crops.

Exposure and sensitization: how a weed allergy develops

When your body develops an allergy after repeated exposure, that's called sensitization. If you live somewhere cannabis is grown, you'll probably face a higher risk of developing allergic reactions down the line. Pollen generally comes from male plants, but hermaphrodite females with male flowers can also release pollen into the air.

Sensitization can also come from using cannabis (in any form) or simply from touching the plant's leaves. In a Spanish study, many patients at an allergy clinic underwent cannabis skin tests. Researchers found that, on average, weed smokers reacted more often than non-smokers, and that reactions were even more common among regular users.

Weed allergy and other allergies: is there a link?

A 2018 study suggested that people allergic to cat dander, mold, dust mites or other plants may be more likely to be allergic to cannabis.

It was a small study, so don't treat it as the final word. More research is needed to confirm the results, but if you have any of those allergies, it's worth keeping in mind.

Along the same lines, certain food allergies may make a cannabis allergy worse, specifically with foods whose proteins are similar to the plant's. Why? These foods can “cross-react” with cannabis and trigger what's known as cannabis-fruit-vegetable syndrome. Here are some foods that may cross-react with the plant:

• Tomatoes
• Apples
• Bananas
• Peaches
• Eggplant
• Almonds
• Chestnuts
• Citrus fruits

How is a cannabis allergy diagnosed?

There's still no standard way to test for a cannabis allergy. Doctors usually rely on a careful medical history.

Skin tests may be an option for patients with a history of allergic reactions to cannabis. An allergist could, for example, make an extract or slurry from the plant's buds, leaves and flowers, then run a regular skin-prick test like any standard allergy test. These tests aren't standardized, but in general they can be used to predict allergic sensitization.

Blood tests are another route. Clínica Subiza in Madrid, Spain, is one of the best-known clinics for this: with a simple blood test it can detect sensitization not only to cannabis but to its main allergen, Can s 3.