Behçet's Disease: This condition is characterized by recurrent aphthous ulcers along with other manifestations such as uveitis, arthritis, and skin lesions including urticaria. The combination of urticaria and aphthous ulcers is a strong indicator for Behçet's Disease due to its classic presentation.

Systemic Lupus Erythematosus (SLE): SLE can present with a wide range of symptoms including urticaria and oral ulcers. The disease's autoimmune nature can lead to various skin and mucosal manifestations.
Urticarial Vasculitis: This condition involves inflammation of the blood vessels and can present with urticaria-like lesions that can be distinguished by their longer duration and potential for leaving scars. Oral ulcers can also be a part of the presentation.
Inflammatory Bowel Disease (IBD): Both Crohn's disease and ulcerative colitis can have extraintestinal manifestations, including skin lesions like urticaria and oral aphthous ulcers.

Wegener's Granulomatosis (Granulomatosis with Polyangiitis): Although less common, this condition can present with a wide range of symptoms including skin lesions and oral ulcers. It is critical to diagnose early due to its potential for severe organ damage.
Malignancy: Certain types of cancer, such as lymphoma, can present with skin manifestations including urticaria and oral ulcers. Early diagnosis is crucial for treatment and prognosis.

Sjögren's Syndrome: Primarily known for its effects on exocrine glands, Sjögren's can also present with skin and mucosal manifestations, including urticaria and oral ulcers, though this is less common.
Sweet Syndrome (Acute Febrile Neutrophilic Dermatosis): Characterized by fever, neutrophilia, and tender erythematous skin lesions, Sweet Syndrome can occasionally present with oral ulcers and might be considered in the differential diagnosis of urticaria with aphthous ulcers, especially in the context of systemic symptoms.