Lyme disease is a common tick-borne infection in Europe, with erythema migrans serving as the primary clinical criterion for early diagnosis. However, many patients do not recall a tick bite, and early cutaneous manifestations may lack the classic annular or target-like appearance. Such atypical lesions can resemble allergic dermatitis, cellulitis, or fungal infection, contributing to diagnostic delay in family medicine. Early recognition in primary care is essential, as prompt antimicrobial treatment prevents progression to neurological, cardiac, or musculoskeletal complications.We report the case of a woman in her 50s who presented with a 6–7 day history of fatigue, low-grade fever, diffuse headache, and a 7–8 cm erythematous patch on the lateral thigh. She did not recall a tick bite but reported frequent outdoor gardening. The lesion was non-pruritic, irregularly shaped, and poorly demarcated without central clearing. It was initially diagnosed as allergic dermatitis, and topical corticosteroids were prescribed. Persistent symptoms and lesion enlargement prompted re-evaluation four days later. Serologic testing (ELISA) was performed, and empirical doxycycline was initiated based on clinical suspicion. Clinical response and follow-up outcomes were monitored.This case highlights an atypical presentation of early Lyme disease mimicking allergic dermatitis in a patient without a known tick bite. It emphasizes the diagnostic challenges posed by non-classic erythema migrans and demonstrates the limited utility of early serologic testing, which may yield false-negative results.Atypical erythema migrans can occur without the characteristic annular morphology, and absence of a recalled tick bite does not exclude Lyme disease. Early serology may be negative, making clinical judgement crucial. Empirical treatment based on clinical suspicion can prevent progression to disseminated disease. Future efforts in primary care should focus on improving clinician awareness of atypical presentations and enhancing diagnostic pathways.This case illustrates the diagnostic complexity of early Lyme disease when cutaneous findings are subtle or misleading. The initial misclassification as dermatitis reflects common challenges in primary care. Reassessment incorporating symptom progression, epidemiological exposure, and lesion evolution enabled timely diagnosis and treatment.Atypical erythema migrans may lead to diagnostic delay. Careful clinical assessment and early empirical therapy are essential to prevent disease progression.