Can iron tablets cause a rash?

Can Iron Tablets Cause a Rash?

Yes, iron tablets can cause a rash, though this is a rare adverse effect that occurs more commonly with intravenous iron formulations than with oral iron supplements.

Oral Iron and Rash

Oral iron supplements (ferrous sulfate, ferrous gluconate, ferrous fumarate) primarily cause gastrointestinal side effects rather than dermatologic reactions 1. The most common adverse effects of oral iron include:

• Dyspepsia, nausea, and constipation due to unabsorbed iron in the gastrointestinal tract 2
• Gastric mucosal injury and ulceration from direct corrosive effects 3
• No significant evidence linking oral iron tablets to systemic rash or skin reactions in the medical literature reviewed

The gastrointestinal side effects occur in a dose-dependent manner, which is why taking iron once daily or every other day is recommended to improve tolerance 1.

Intravenous Iron and Rash

Rash is a documented but uncommon adverse effect of intravenous iron preparations:

• In a randomized study of 145 patients receiving iron sucrose, only one adverse event (skin rash) in a single patient was considered related to the study drug 1
• A case report documented an exanthematous (morbilliform/maculopapular) drug eruption occurring two days after ferumoxytol 510 mg intravenously, representing a delayed type IV hypersensitivity reaction that resolved with corticosteroid treatment 4
• Pruritus (itching) is listed as a known side effect of iron infusions, though most reactions are mild and self-limited 5

Important Clinical Distinctions

Iron deficiency itself can cause pruritus without rash, which is distinct from a drug reaction to iron supplementation:

• Iron deficiency anemia is a common cause of generalized pruritus, accounting for 25% of all patients with pruritus due to systemic disease 6
• The British Association of Dermatologists specifically lists disorders of iron metabolism as a cause of generalized pruritus without rash 7
• Iron replacement therapy often leads to complete cessation of pruritus in iron-deficient patients 7, 6

Risk Factors for Adverse Reactions to IV Iron

When rash or other adverse reactions occur with intravenous iron, certain factors increase risk:

• Patients with collagen diseases have an increased incidence of adverse effects 1
• High-molecular-weight iron dextran (Dexferrum) causes more adverse events than newer formulations 5
• Newer iron compounds (iron sucrose, iron gluconate, iron carboxymaltose) have fewer adverse effects than iron dextran 1, 5

Clinical Recommendations

If a patient develops a rash after starting iron supplementation:

• Determine whether the patient is taking oral or intravenous iron, as IV formulations are more likely to cause systemic reactions 1, 4
• Consider whether the patient had pre-existing iron deficiency causing pruritus that may now be improving with treatment 7, 6
• For confirmed drug-induced rash from IV iron, treatment with corticosteroids (methylprednisolone 40 mg IV twice daily for 3 days, followed by oral prednisone taper) has been effective 4
• Switch to a different iron formulation if the reaction is mild, as cross-reactivity between different IV iron preparations is not universal 1

Critical Caveat

The serious hypersensitivity reactions with newer IV iron preparations are very rare (38 incidents per million administrations), and true allergic reactions to IV iron are extremely uncommon—most reactions are complement activation-related pseudo-allergy rather than true allergy 1, 5.