Final answer:
The most suitable next step in treating a 9-year-old with persistent allergic rhinitis and eczema is to introduce a topical corticosteroid cream for the eczema and possibly seek an allergy specialist's advice for adjusting the current antihistamine and anti-inflammatory therapy.
Step-by-step explanation:
The most appropriate treatment for a 9-year-old patient who continues to experience symptoms of allergic rhinitis and eczema despite avoidance therapy and treatment with oral cetirizine and nasal flunisolide would likely involve stepping up the therapy. Since the current regimen is not providing relief, the addition of a topical corticosteroid cream for the eczema on the face and lower extremities might be beneficial. Topical corticosteroids, such as hydrocortisone, can reduce inflammation and alleviate itching and rashes associated with eczema.
For the nasal symptoms, which include nasal congestion, sneezing, and rhinorrhea, a consultation with an allergist may be warranted for further evaluation. The allergist might suggest therapy adjustments, such as a different class of antihistamines, the addition of anti-leukotriene drugs, or even the use of systemic corticosteroids. It's also important to reassess the patient's environment to ensure that all possible allergens are being adequately avoided.