If you’ve recently tried weed for the first time expecting medicinal relief but instead found yourself swelling, sneezing, or rubbing itchy eyes, you may have a weed allergy.

Symptoms

The symptoms of a cannabis allergy are similar to the seasonal allergies and include the following:

runny nose
sneezing
itching
swelling
watery eyes
rashes
hives

In severe cases, anaphylaxis can develop. This acute allergic response to cannabis most typically occurs after the ingestion of hemp seeds. So what exactly is anaphylaxis? It can result in swelling of the throat, difficulty breathing, and passing out. If not treated immediately, anaphylaxis can be fatal. If you suspect that you may have an allergy to cannabis, talk to your doctor about carrying an epinephrine injection in case you go into anaphylactic shock.

Diagnosis

Because of marijuana’s legally gray status (it is federally prohibited but legalized in most states), and complicated and diverse biochemical architecture, finding a clinic that will test might be tricky. [caption id="attachment_16215" align="alignnone" width="1254"]

Skin prick allergy test. Source: iStock[/caption] People who suspect that they have an allergy may be able to take a skin prick or blood test. Leaves, buds, and flowers from the C. sativa plant may be used in a skin prick test. Blood tests are less common, less reliable, and more cost prohibitive.

Treatment

The lack of research on cannabis immunotherapy makes it difficult to prescribe a standard treatment plan. This will likely remain the case until federal cannabis prohibition is lifted—it is nearly impossible for researchers to access cannabis for the scientific discovery needed to develop this kind of therapy. Consequently, the best way to treat a cannabis allergy is to avoid coming into contact with it if you suspect you may be allergic. If you do experience an allergic reaction, contact your doctor. Depending on the severity of the reaction, your doctor will likely prescribe an antihistamine to assist in managing the symptoms.

Allergic reactions should resolve on their own within weeks once cannabis exposure is eliminated.

If you work in a cannabis processing or producing facility or you otherwise cannot avoid coming into contact with the plant, the use of antihistamines, gloves, facemasks, and inhalers may reduce the severity of your symptoms. Because of the small likelihood of developing anaphylaxis, it is important to consult with your doctor about risk management.

Cannabis is an Allergen

Cannabis sativa, like all other plants, contains pollen, an extremely pervasive and irritating allergen subtype. It also contains proteins common to other plants that have been implicated in the development of food allergies. Recent studies show that Can s 3, the nsLTP (non-specific lipid transfer protein) of Cannabis sativa constitutes an important allergen because Can s 3-based diagnostics displays the best performance. Consequently, sensitization to the allergen Can s 3, the ns‐LTP from Cannabis sativa, could lead to a broad variety of cross‐reactions. This essentially means the possibility of cross‐reactivity with tobacco, natural latex and plant‐food‐derived alcoholic beverages. In a 2019 report, Canadian researchers describe possible allergens responsible for cannabis allergy include THC, 4 nonspecific lipid transfer protein (Can s 3),5, 6 and others. An interesting preliminary study in 2018 demonstrated that marijuana use is associated with sensitization to specific allergens, including molds, dust mites, plants, and cat dander. In lay terms, use of marijuana can create sensitivities to the above allergens that did not otherwise exist in the user. The authors propose to use the sIgE hemp assay (crude extract using an ImmunoCAP technique) where there’s a suspicion of a cannabis allergy as a negative result makes a cannabis allergy unlikely. However, a positive sIgE hemp always needs additional diagnostic work-up with a Can s 3 based diagnostic. Clearly, more research needs to be done to establish IgE reactivity profile in Cannabis sativa.

Are Cannabis Allergies Becoming More Common?

With the rapid growth of the legal cannabis industry comes increased opportunity for exposure. In addition to the cannabis used for medicinal purposes, hemp (a non-psychoactive variety of the Cannabis sativa plant) is used in thousands of products. According to the American Academy of Allergy Asthma and Immunology (AAAAI), this makes exposure and subsequent sensitization to cannabis extremely common. People may develop a sensitivity to cannabis by consuming or touching cannabis products. The AAAAI predicts that reports of cannabis allergies will become increasingly prevalent as the industry expands. Notwithstanding the medically-based utilization of cannabis the augmented interest for highly nutritious foods has increased the widespread availability and use of hemp seeds ( a super-food high in protein)in the food industry, which can contribute to the frequency of hemp seed allergy and possibly cannabis cross-reactivity. In addition to hempseed and hempseed oil, derivatives of dried flowers or resinous extract can be incorporated in food and ingested. Since both hemp and cannabis can induce clinically relevant allergic cross-reactivity one can get a hemp allergy without being exposed to hemp which can in turn manifest as severe anaphylaxis or other lesser symptoms.

Why you don't hear about cannabis allergies

A 2016 Photodetection in Flow Cytometry review determined that the prevalence of cannabis allergies is likely underreported due to the plant’s illegality in some states and in federal law. The authors explained that far more people than the public may be conscious of are at risk of developing cannabis sensitivity. Those groups include but aren't limited to:

Police officers who seize illegal pot
Recreational users who inhale or ingest cannabis products
Cannabis growers
Laboratory scientists who test the plant

Others could inhale cannabis allergens while walking the street or come into contact with pot when in proximity to someone actively using cannabis products. Skin-to-cannabis contact may result in urticaria (rash) or contact dermatitis, inhaling cannabis may result in season allergy-like respiratory irritation, and ingesting cannabis may lead to gastrointestinal discomfort, swelling, and in severe cases, anaphylaxis.

If You are Allergic to These Things, You May be Allergic to Cannabis

A 2017 Revue de Pneumologie Clinique review found that cannabis allergies may be triggered by foods that have a similar chemical composition to weed. This phenomenon is known as cross-allergy or cross-reactivity. It occurs when the body has an allergic reaction to one food, but then becomes sensitive to other foods or plants that contain similar proteins to the original allergy inducing plant. If you have a history of allergies, you can use your knowledge about your food sensitivities to make an educated guess about the likelihood of developing a cannabis allergy. Certain foods contain a molecular composition similar to marijuana. If you have an allergy to any of the following foods, you may be sensitive to cannabis as well:

tomatoes
nuts
apple
peaches
bananas
grapefruit
orange
chestnuts
eggplant