Which of the following antihistamine classes can be used as monotherapy for allergic rhinitis?

The correct answer is that all of the classes mentioned can effectively be used as monotherapy for allergic rhinitis.

First-generation antihistamines are known for their ability to alleviate the symptoms of allergic rhinitis, although they may have sedating effects due to their ability to cross the blood-brain barrier. This can be beneficial in certain scenarios where sedation is desired but may be a drawback for patients needing to remain alert.

Second-generation antihistamines are preferred in many cases due to their reduced sedation and longer duration of action. They are non-sedating for most patients and are often recommended as first-line treatments for allergic rhinitis, effectively managing symptoms without the drowsiness associated with their first-generation counterparts.

Intranasal antihistamines provide localized treatment directly in the nasal passages, leading to rapid relief of symptoms such as congestion, sneezing, and runny nose. They are particularly useful for patients who may have more significant nasal symptoms and can be used alone or in combination with other therapies.

Given the efficacy of all these classes in managing allergic rhinitis symptoms, each can be selected as a monotherapy option depending on the individual patient's needs and preferences, thus supporting the idea that all of the mentioned classes can be appropriate choices.