Viral Upper Respiratory Tract Infection (URTI): This is the most common cause of the symptoms described, including blue eye discharge (likely referring to a purulent or mucopurulent discharge), ear pain due to Eustachian tube dysfunction, and a stuffy nose. Viral URTIs are highly prevalent and can cause these symptoms due to the viral infection itself or secondary bacterial infections.

Bacterial Sinusitis: Can cause a stuffy nose, facial pain, and if the infection spreads, could lead to ear pain and eye discharge. The discharge from the eye might not typically be described as blue, but in the context of a severe infection, it could be purulent.
Allergic Rhinitis: Though less likely to cause eye discharge described as blue, allergic reactions can lead to a stuffy nose and, in some cases, ear pain due to Eustachian tube dysfunction. The eye symptoms might be more related to itchiness and redness rather than a purulent discharge.
Common Cold: Similar to viral URTI, the common cold can cause a stuffy nose and, occasionally, ear pain. Eye discharge is less common but can occur, especially if there's a secondary infection.

Orbital Cellulitis: A serious infection of the tissues surrounding the eye, which can cause severe eye pain, redness, swelling, and discharge. It's a medical emergency and requires prompt treatment.
Meningitis: Though less directly related to the symptoms described, in rare cases, severe infections can lead to meningitis, especially if there's a spread of infection from the sinuses or ears to the meninges. It's crucial to consider this diagnosis, especially if there are additional symptoms like fever, headache, or stiff neck.
Ludwig's Angina: A severe infection of the tissues in the neck, which can cause difficulty swallowing, neck pain, and in severe cases, can lead to airway obstruction. It's less directly related to the symptoms but is a critical diagnosis not to miss due to its potential for airway compromise.

Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A rare autoimmune disorder that can cause a variety of symptoms, including sinusitis, eye inflammation, and in some cases, ear symptoms. It's much less common and would typically present with additional systemic symptoms.
Relapsing Polychondritis: A rare disease that causes recurring episodes of cartilage inflammation, which can affect the ears, nose, and eyes. It might cause some of the symptoms described but is quite rare and usually presents with other distinctive features like cartilage destruction.