RATIONALE: Marijuana can be used through inhalation or through oral ingestion. Allergy to marijuana is considered rare, but a few reports of allergies to marijuana have been documented and lipid transfer protein was recently identified as an allergen, in one case. Here we report seven patients that presented with allergic symptoms associated with marijuana exposure. METHODS: A detailed history of exposure to marijuana and symptoms was taken from each patient. Skin prick tests (SPT) were used to confirm allergy to marijuana, using the bud or flower of the marijuana plant. RESULTS: All seven patients had large positive SPT with wheals larger than 5 mm and surrounding flare, confirming their allergy to marijuana. Six patients presented with inhalation symptoms with exposure to marijuana. Inhalant symptoms included rhinitis and conjunctivitis in five, periorbital angioedema in three, sinusitis in two, wheezing in two, and swelling of the throat sensation in one case. Six of the patients also presented with contact symptoms which included five occurrences of urticaria, one of periorbital angioedema, and one of dermatitis. One patient presented with anaphylaxis symptoms which included anxiety, tightness of chest, wheezing, GI cramping and vomiting with ingestion of a marijuana tea. CONCLUSION: It appears that marijuana may be a much more common allergen than previously thought. Allergic reactions to marijuana may become more of an issue in the future given the increasing social use of marijuana, as well as its expanding medical use. It is important that marijuana exposure is addressed when assessing a patient's exposure history.