What is the most common predisposing factor for orbital cellulitis?

The most common predisposing factor for orbital cellulitis is bacterial sinusitis. This condition typically arises from the spread of infection from the paranasal sinuses, particularly the maxillary and ethmoid sinuses, into the orbit. The anatomy of the face means that the sinuses are closely connected to the orbital cavity, allowing bacteria to easily migrate in cases of sinus infections.

In essence, when a patient has bacterial sinusitis, the inflammation and infection in the sinuses can lead to complications, including the development of orbital cellulitis. This is a serious condition that requires timely intervention, often including antibiotic therapy and sometimes surgical drainage if there are abscesses or significant complications.

Other factors, such as trauma to the eye, could also lead to orbital cellulitis but are less common as an underlying cause comparing to sinusitis. Viral infections and allergic rhinitis do not directly lead to bacterial infections that cause orbital cellulitis; they typically do not have the same risk for progression to such a serious condition.