Systemic hypersensitivity to acacia gum as a pharmaceutical excipient: a case report

Background Acacia gum (E414), derived from Acacia senegal , is a water-soluble emulsifier used in food and pharmaceuticals for its stabilizing properties [1–3]. Hypersensitivity reactions are mainly reported in occupational settings and are thought to be IgE-mediated, though the specific epitope is unknown [1–5]. No cases of allergic reactions due to ingestion have been documented in the literature. Case presentation A 37-year-old man with hypothyroidism and migraines presented with a 10-year history of episodic headaches, weakness, nasal congestion, and presyncope. Extensive investigations, including sinus surgery, immunotherapy, migraine and seizure treatments, and dietary changes, were unsuccessful. His symptoms resolved after discontinuing Synthroid, raising suspicion of an excipient-related reaction. Acacia gum, an inactive ingredient in Synthroid, was identified as a potential trigger. Switching to compounded levothyroxine without acacia gum led to sustained symptom resolution. A self-administered challenge to acacia gum induced throat tightness, dyspnea, tongue swelling, and near-syncope within 15 min. Skin prick testing was negative to Synthroid and pure levothyroxine. Intradermal testing was positive to Synthroid (6 mm wheal, 12 mm flare) and acacia gum (50 mm wheal), but negative to pure levothyroxine. A placebo-controlled oral challenge to Synthroid induced symptoms 10 min after ingestion of 7.5 mcg (10% of usual dose). Oral challenge to 0.5 g acacia gum reproduced similar symptoms. Conclusions This case highlights the importance of evaluating excipients as potential allergens in patients with unexplained or multisystem symptoms. Ingestion of acacia gum may cause systemic allergic reactions, even without prior reported cases. Clinicians should be aware of formulation differences between commercial and compounded medications when assessing drug-related reactions.