Urticaria is a disease characterised by lesions, including wheals and angioedema. It can be divided into acute and chronic. Determining the aetiology of urticaria is often challenging; however, according to current guidelines, additional tests are not required in the acute form of the disease. This paper presents the case of a 14-year-old boy with urticaria, where treatment with second-generation antihistamines and systemic glucocorticosteroids did not alleviate the symptoms. Following further diagnostics, including a computed tomography scan of the sinuses, chronic sinusitis was considered a potential cause of the symptoms. This case exemplifies a situation where targeted diagnostics focusing on potential infection led to effective treatment of the underlying cause. Therefore, in clinically justified cases – especially those with atypical presentations of urticaria – searching for the underlying cause seems warranted. The article can contribute valuably to the discussion on current recommendations and foster a more individualised diagnostic and therapeutic approach to urticaria.