Can Helicobacter pylori (H. pylori) infection cause elevated eosinophil count (eosinophilia)?

Can H. pylori Cause Eosinophilia?

H. pylori infection can cause localized tissue eosinophilia in the gastric mucosa but does not typically cause peripheral blood eosinophilia (elevated absolute eosinophil count of 12% would be unusual and requires evaluation for other causes).

Gastric Tissue Eosinophilia vs. Peripheral Blood Eosinophilia

H. pylori infection is associated with increased eosinophil infiltration specifically in gastric tissue, not systemic eosinophilia. Research demonstrates that H. pylori-infected gastric mucosa shows a statistically significant increase in eosinophils compared to H. pylori-negative gastritis 1. The bacteria induce eosinophil migration through the cag pathogenicity island, which stimulates gastric epithelial cells to produce chemokines (CCL2, CCL5, and granulocyte-macrophage colony-stimulating factor) that recruit eosinophils to the gastric mucosa 2.

• Eosinophils redistribute in H. pylori-infected gastric mucosa, with increased density in the superficial lamina propria just below the foveolar epithelium, and can even enter the epithelium itself and the lumen of foveolae near bacteria 3
• The H. pylori-derived peptide Hp(2-20) directly stimulates eosinophil migration and induces production of VEGF-A and TGF-beta, suggesting eosinophils may play a role in gastric mucosal repair during infection 3

Why Peripheral Eosinophilia (12%) is Unlikely from H. pylori Alone

A peripheral blood eosinophil count of 12% is elevated and requires systematic evaluation for other causes beyond H. pylori. The evidence shows that H. pylori causes localized gastric tissue eosinophilia but not the degree of peripheral blood eosinophilia you're describing.

Primary causes to evaluate for peripheral eosinophilia include:

• Parasitic infections (particularly intestinal helminths) - the second most common cause of eosinophilia after allergic disorders 4
• Allergic disorders - account for approximately 80% of eosinophilia cases, including asthma, food allergies, and atopic dermatitis 4
• Eosinophilic gastrointestinal disorders - particularly eosinophilic esophagitis (EoE), though peripheral eosinophilia occurs in only 10-50% of adults with EoE and is usually modest (2-fold elevation) 4
• Hypereosinophilic syndrome (HES) - defined by persistent peripheral blood eosinophilia >1500 cells/μL with organ damage 5

Clinical Approach to This Patient

Obtain a comprehensive workup for eosinophilia while treating the H. pylori infection:

1. Stool examination for ova and parasites and Strongyloides serology to exclude parasitic infections 5
2. Detailed medication review - many drugs can cause eosinophilia 5
3. Assess for allergic conditions - history of asthma, allergic rhinitis, eczema, food allergies 4
4. Consider eosinophilic gastrointestinal disorders - if the patient has dysphagia, food impaction, or other GI symptoms beyond those typical of H. pylori gastritis 4
5. CBC with differential monitoring - if eosinophilia persists after H. pylori eradication, further workup for HES may be warranted 5

Important Caveats

• H. pylori does NOT protect against eosinophilic esophagitis - a large prospective case-control study of 808 patients found no inverse association between H. pylori infection and EoE 6
• Treat the H. pylori regardless - patients with atrophic gastritis should be tested for H. pylori and treated if positive, with subsequent non-serologic testing to confirm eradication 7
• The eosinophilia may resolve after H. pylori eradication if it's contributing - one study showed decreased gastric juice eosinophilic cationic protein and gastric eosinophil infiltration after H. pylori eradication in patients with chronic urticaria 8, though this was localized tissue response, not peripheral eosinophilia

The 12% peripheral eosinophilia warrants investigation beyond H. pylori infection alone, as this degree of systemic eosinophilia suggests an additional underlying cause that requires identification and management.