marijuana

Study: Cannabis Allergy Underreported Despite Widespread Use

Cannabis, like other pollen-bearing plants, can cause allergic reactions ranging from allergic rhinitis to anaphylaxis, a fact that is underreported despite the widespread use of the substance, according to a new study.

In an effort to better understand the risk of allergic reaction associated with Cannabis use and exposure, researchers conducted a review of available literature on the subject. The review included both case reports of allergic reaction and studies on the allergic qualities of the substance, diagnosis methods, and treatment options.
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Overall, reported reactions included:

  • Allergic rhinitis, conjunctivitis, asthma, nasal congestion, sneezing, pharyngeal pruritus, coughing, wheezing, and dyspnea—reactions commonly seen in other plant aeroallergens—with exposure to both Cannabis pollen and Cannabis smoke.
  • Urticaria, generalized pruritus, and periorbital angioedema with cutaneous handling of the plant itself.
  • Anaphylaxis, urticaria, angioedema, dyspnea, and dysphonia after hemp seed ingestion. 
  • Allergic asthma triggered by occupational exposure to Cannabis.
  • A single case of bronchopulmonary aspergillosis attributed to fungal contamination of marijuana samples.
  • Anaphylaxis after intravenous marijuana use.

Researchers cautioned that the rates of allergic reaction may in fact be higher than reported, noting that "the illicit nature of Cannabis use can create barriers for accurate and clear patient reporting."

While avoidance—as with other allergens—is the recommended form of treatment, antihistamines, intranasal steroids, and nasal decongestants may also be used to alleviate symptoms of allergic rhinoconjunctivitis, β-agonists may be used to treat symptoms of asthma, and epinephrine should be prescribed to patients with a history of anaphylaxis, according to researchers.

“Although still relatively uncommon, allergic disease associated with [Cannabis] exposure and use has been reported with increased frequency,” they concluded. 

“Much research is still needed to more definitively define pertinent allergens, develop a standardized extract, establish diagnostic sensitivity and specificity, and clarify treatment options for clinically affected Cannabis-allergic patients.”

—Michael Potts

Reference:

1. Ocampo TL, Rans TS. Cannabis sativa: the unconventional "weed" allergen. Ann Allergy Asthma Immunol. 2015;114(3):187-192