We report two cases of recurrent episodes of hoarseness, cough, flushing, pruritus, and rash occurring within 30 minutes of topical exposure to carbonless copy paper. Provocative challenges revealed that alkylphenol novolac resin was the ingredient responsible. Video endoscopy of the larynx was performed and plasma histamine levels were obtained prior to and 30 minutes after cutaneous challenge of a patient with alkylphenol novolac resin. We documented marked laryngeal edema and a sixfold increase in plasma histamine levels after challenge. We conclude that topical exposure to carbonless copy paper may cause mast cell/basophil-mediated acute systemic and potentially life-threatening reactions in susceptible patients.