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Allergy to Marijuana

IgE-mediated Cannabis (C. sativa, marihuana) allergy seems to be on the rise. Both active and passive exposure to cannabis allergens may trigger a C. sativa sensitization and/or allergy. The clinical presentation of a C. sativa allergy varies from mild to life-threatening reactions and often seems to depend on the route of exposure. In addition, sensitization to cannabis allergens can result in various cross-allergies, mostly for plant foods. This clinical entity, designated as the ‘cannabis-fruit/vegetable syndrome’, might also imply cross-reactivity with tobacco, natural latex and plant-food-derived alcoholic beverages.

At present, diagnosis of cannabis-related allergies predominantly rests upon a thorough history completed with skin testing using native extracts from crushed buds and leaves. However, quantification of specific IgE antibodies and basophil activation tests can also be helpful to establish correct diagnosis. In the absence of a cure, treatment comprises absolute avoidance measures.

When cannabis is used for its psychoactive effects, drug (ab)users may become sensitized by inhalation of cannabis allergens through active smoking and/or vaporizing the drug. Cutaneous contact through handling of the drug is another possible route of sensitization.

C. sativa produces wind-borne pollen easily transported over long distances. However,  as only female (nonpollinating) plants are cultivated for illicit use, it is less likely for abusers of cannabis, who grow their own plants, to become sensitized to marihuana through pollen exposure.

The clinical presentation of an IgE-mediated cannabis allergy can vary considerably from mild to life-threatening reactions and seems to relate to the route of exposure. First, respiratory reactions like rhinitis, conjunctivitis, asthma and palpebral angioedema have been described. These reactions predominantly occur when cannabis is consumed by smoking or vaporizing.

Cross-reactivity between cannabis and plant-derived food has been described in multiple studies and was recently designated as the ‘cannabis-fruit/vegetable syndrome’. The foods most commonly implicated in this allergy syndrome are peach, apple, nuts, tomato and occasionally citrus fruit as orange and grapefruit.

It is important to note that the allergic reactions to these plant foods are often triggered or exacerbated by cofactors such as exercise or nonsteroidal anti-inflammatory drugs (NSAIDs) and are therefore variable which can make history taking more complex. Furthermore, these reactions are frequently more severe than the classic oral allergy syndrome (OAS) expected in food allergy related to sensitization to tree, grass or ragweed pollen.

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