A 31-year-old male was referred to our community allergy practice for assessment of suspected cannabis allergy. He had previously experienced several episodes of localized pruritus and erythema after direct contact with various strains of cannabis and noted that the severity of his reaction appeared to be strain dependent. He had developed a severe local reaction involving bilateral periorbital edema shortly after coming into direct contact with one particular strain of cannabis (believed to be Blue Moonshine, but patient uncertain). This particular episode was also associated with dyspnea in the absence of any other systemic symptoms. For this reaction he presented to a local emergency department and was treated with antihistamines and corticosteroids with good effect. He had never had an immediate reaction after smoking cannabis. After this particular episode and prior to his allergy consultation, he continued to smoke cannabis without adverse reaction but tried to avoid direct contact, particularly with his mucous membranes. His past medical history was notable for asthma and seasonal rhinoconjunctivitis.

The patient was diagnosed with recurrent local allergic reactions after direct contact with cannabis and he had a suspected selective cannabis strain allergy based on his clinical history. Skin testing was performed to environmental inhalants and the patient had positive reactions to dust mite, grass pollens and various tree pollens. The patient also brought in multiple strains of cannabis for skin testing including “Blue Moonshine” (Cannabis indica dominant strain), “Blue Dream” (Hybrid strain that is largely Cannabis sativa dominant), “Sweet Island Skunk” (Cannabis sativa dominant strain), “Sweet Skunk” (Hybrid) and “Blueberry Haze” (Hybrid). The cannabis strains where mixed with small aliquots of water for skin testing. Fresh testing was required due to the absence of commercially available abstracts. He had positive testing to the strains “Blue Dream” (7 mm), “Sweet Island Skunk” (10 mm) and “Blueberry Haze” (6 mm) while he had negative testing to “Blue Moonshine” and “Sweet Skunk” (Table 1). Histamine and saline controls were appropriate (3 mm and 0 mm respectively).

The patient was advised to avoid direct cutaneous or mucosal contact with cannabis due to his reported clinical history and skin testing. Due to the inconsistences in strain identification by history and skin testing, he was advised to avoid all strains. An epinephrine autoinjector was prescribed in case he developed a more severe systemic reaction on repeat exposure. A telephone follow-up visit was conducted 6 months after the initial consultation. The patient endorsed that he was still smoking cannabis regularly but had not had any new significant reactions. He continued to use all above tested strains of cannabis in addition to a few new ones. He was still avoiding direct cutaneous and mucosal contact as much as possible.