Hidden Excipients: Uncovering Gluten and Soy in Everyday Medications

A new study out of Portugal is casting light on an often-overlooked risk in commonly used medications: the presence of hidden excipients such as gluten and soy. These substances, while seemingly inert, can carry significant consequences for patients with food allergies or intolerances—and they’re not always disclosed on drug labels.

The findings, focused on widely used over-the-counter painkillers like paracetamol and ibuprofen, raise pressing concerns for clinicians, as well as for those working on the front lines of regulatory policy and patient safety. For providers, the message is clear: vigilance is required not just in what is prescribed, but in how medications are formulated.

Allergens in the Aisle: What the Data Show

The study, as reported by News Medical, analyzed a wide range of paracetamol and ibuprofen products available in Portugal. Researchers found that gluten was present in over half of all solid oral paracetamol products, with film-coated tablets showing the highest rate at 61.1%. Even standard tablets came in at 60%, and 40% of liquid formulations also contained gluten.

Soy-derived excipients were similarly prevalent, appearing in nearly one-third of liquid oral formulations and rectal suppositories. Specifically, 30% of paracetamol liquids, 33.3% of suppositories, and 26.7% of NSAID liquids included soy-based components.

For patients with celiac disease or soy allergies, exposure to even trace amounts of these excipients can trigger adverse reactions. And for clinicians, these exposures often go undetected—not due to oversight, but because the risks are literally hidden in the fine print, or not mentioned at all.

Clinical Implications: More Than Just a Label

These findings reinforce a broader truth about pharmaceutical excipients: they are not always inert, and their inclusion can be clinically relevant. Allergists and primary care physicians alike must now consider not just the active pharmaceutical ingredient, but also what might be lurking in the formulation.

Consider the case of a child with a soy allergy who is prescribed a liquid NSAID postoperatively, or a patient with celiac disease managing chronic pain with over-the-counter paracetamol. If the excipient profile is not verified, what begins as routine care could end in an allergic reaction.

The need for proactive discussion around formulation safety is especially important in vulnerable populations—pediatrics, geriatrics, and those with chronic conditions requiring polypharmacy. For this reason, enhanced awareness among prescribers is critical.

Labeling Gaps and Regulatory Blind Spots

The study’s authors call for immediate improvements in medication labeling standards. Unlike food products, which are strictly regulated to disclose common allergens, pharmaceutical products often lack the same transparency. In many countries, regulations do not mandate full disclosure of inactive ingredients, especially when they fall below certain thresholds.

But for sensitive patients, thresholds don’t always matter. Trace exposure can still prompt reactions, underscoring why current labeling practices fall short. As regulatory bodies such as the EMA and FDA reconsider labeling frameworks, the inclusion of allergen disclosures could mark a pivotal shift toward safer prescribing.

A Call for Broader Inquiry

While this study focused specifically on paracetamol and ibuprofen, it raises questions that extend across the pharmaceutical spectrum. How widespread is the use of allergenic excipients in other drug classes—antibiotics, antidepressants, or antiepileptics? How often are reactions attributed to drug intolerance when they might stem from an excipient?

These questions highlight the need for expanded pharmacovigilance that includes excipient tracking. Moreover, pharmaceutical manufacturers may face mounting pressure to reformulate products or, at the very least, offer allergen-free alternatives when possible.

Toward a Safer, More Transparent Future

As clinicians, the next step is education—both self-directed and patient-centered. Pharmacists, too, play a pivotal role in flagging excipient risks during dispensing. Until regulatory changes catch up, healthcare providers remain the final safeguard against unintentional allergen exposure.

The Portuguese study is more than a cautionary tale—it’s a prompt for action. Ensuring that medications are safe for every patient means demanding clarity, pushing for reform, and treating excipients not as afterthoughts, but as integral parts of clinical decision-making.