There are many reports in the literature of adverse reactions to excipients.1-3 These include skin rashes induced by the coloring agent in the capsule shell of rifampicin2 and a rash that developed from a coloring agent in oral iron.3 Other reports have noted dyes in foods and even toothpaste as triggers.4,5
Hypersensitivity. Although a specific reaction to prednisone was considered unlikely in this case, type IV delayed hypersensitivity reactions to corticosteroids have been reported. The most common type of corticosteroid-related allergy is contact dermatitis associated with topical corticosteroid use.6 Many cases of delayed maculopapular reactions are thought to be T-cell–mediated type IV reactions.6
Type I immediate hypersensitivity reactions to corticosteroids are also well documented. In a literature review of 120 immediate hypersensitivity reactions to corticosteroids, anaphylactic symptoms were more commonly reported than urticaria or angioedema.7 Intravenous exposure was most frequently associated with reactions, followed by the intra-articular and oral routes of administration.7
Causative agents. The same literature review identified methylprednisolone as the most common steroid to cause a reaction; dexamethasone and prednisone were the least frequently associated with reactions.7 Pharmacologically inactive ingredients were implicated in 28% of the corticosteroid hypersensitivity reactions.7
Additives suspected to be triggers include succinate and phosphate esters, carboxymethylcellulose, polyethylene glycol, and lactose. Interestingly, there have been reports of acute allergic reactions to methylprednisolone sodium succinate 40 mg/mL intravenous preparation in children with milk allergy, due to lactose contaminated with milk protein.8,9
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