Aim: Amoxicillin rash is a generalized maculopapular exanthema that occurs after the use of semisynthetic penicillins in the treatment of patients with clinically unrecognized infectious mononucleosis. Such patients are often misdiagnosed as allergic to penicillin. The aim of this study was to present the rash that occurred in a girl treated with amoxicillin due to the signs of upper respiratory tract inflammation. She did not have the typical clinical presentation of infectious mononucleosis. Case report: A four-year-old girl presented with acute symptoms of catarrhal inflammation of the upper respiratory tract and fever up to 39.7°C with chills and shivering, to which amoxicillin was introduced. After the first dose of amoxicillin, a rash appeared. First on the head, behind the ears, and then diffusely spread “descending” to the trunk and extremities. Due to persistent fever, spreading and confusing rash and sore throat, the girl was hospitalized. Maculopapular erythematous rash, red throat with hypertrophic tonsils, and enlarged angular lymph nodes were present at admission. CRP was 37.1 and blood count was marked by relative neutrophilia. It is important to point out normal transaminase values from serum biochemistry. Acute Epstein-Barr virus infection was confirmed by serology. After symptomatic treatment, the skin symptoms gradually subsided. The patient became afebrile on the fourth day of hospitalization, and was discharged home on the sixth day. Conclusion: The pathogenesis of this skin rash is still insufficiently investigated. It is most often a transient immune reaction due to a viral infection, and not a real allergic reaction to amoxicillin, which is most often mistakenly suspected in practice. In conclusion, infectious mononucleosis should be suspected even when there are no typical clinical signs for the disease, such as lymphocytosis and elevated transaminases.