From the Guidelines

Second-generation antihistamines are the best type of antihistamine for allergic rhinitis.

They have less or no tendency to cause sedation, performance impairment, and anticholinergic effects compared to first-generation antihistamines 1.
Examples of second-generation antihistamines include fexofenadine, loratadine, and desloratadine, which do not cause sedation at recommended doses 1.
Cetirizine and intranasal azelastine may cause sedation at recommended doses, but the effect is generally milder than that observed with first-generation antihistamines 1.

Second-generation antihistamines are generally preferred over first-generation antihistamines due to their lower risk of adverse effects 1.
They are effective in reducing rhinorrhea, sneezing, and itching associated with allergic rhinitis, but have little objective effect on nasal congestion 1.
Intranasal antihistamines, such as azelastine, may be useful alternatives to oral antihistamines, but may cause sedation in some patients and/or have a bitter taste 1.

The use of first-generation antihistamines should be approached with caution, especially in older adults, due to their potential to cause sedation, performance impairment, and anticholinergic effects 1.
Second-generation antihistamines are generally recommended as the first-line treatment for allergic rhinitis, due to their efficacy and safety profile 1.

From the Research

Second-generation antihistamines, such as fexofenadine and bilastine, are recommended for first-line therapy of allergic rhinitis due to their non-sedating properties 2.
Bilastine has a more potent binding affinity to the H₁ receptor and its action tends to last longer compared to fexofenadine 2.
Chlorpheniramine is considered a reasonable initial antihistaminic agent, but a nonsedating antihistamine should be used initially if a patient is involved in activities where drowsiness is dangerous 3.

Both oral and intranasal antihistamines are approved for the first-line treatment of allergic rhinitis and result in a reduction in symptoms and an improvement in quality of life 4.
Intranasal agents may be preferred in patients with nasal congestion or when a more rapid onset of action is desired, while oral agents may be better suited for young children or patients with poor medication compliance 4.

For mild intermittent or mild persistent allergic rhinitis, first-line treatment may include a second-generation H₁ antihistamine (e.g., cetirizine, fexofenadine, desloratadine, loratadine) or an intranasal antihistamine (e.g., azelastine, olopatadine) 5.
For persistent moderate to severe allergic rhinitis, initial treatment should be an intranasal corticosteroid, either alone or in combination with an intranasal antihistamine 5.

Intranasal antihistamines have broad anti-inflammatory effects, involving multiple pathways and mediators, including histamine, leukotrienes, and cytokines 6.
These anti-inflammatory actions may contribute to the effectiveness of intranasal antihistamines in relieving symptoms of nonallergic rhinitis, where histamine has a lesser role 6.