RESUMEN
INTRODUCTION: Giardia intestinalis causes diarrhea and malabsorption, especially in developed countries. Although it primarily affects the gastrointestinal system, on rare occasions it causes allergic symptoms such as itching, urticaria, and eczema. Here we describe the case of a 19-year-old man with no past medical history who presented to our hospital with an atypical urticarial rash. DIAGNOSIS: The only abnormal result in laboratory findings of stool parasitology was G. intestinalis. The patient was diagnosed with urticaria due to giardiasis. INTERVENTION AND OUTCOMES: The patient was prescribed Bilastine tablet 20 mg 1 × 1 and referred to the Infectious Diseases Department for treatment. Co-Trimoxazole 400 mg/80 mg tablets 2 × 1 and Metronidazole 500 mg tablets 3 × 1 were prescribed. The urticaria had disappeared at the follow-up visit. The patient confirmed that urticarial symptoms did not recur. CONCLUSIONS: Despite their rarity, Giardia and other parasite infections can cause allergic symptoms. Parasitic factors should be considered in patients, especially those living in the communal areas, who present with treatment-resistant urticaria.