Phase IIIb , longitudinal, multicenter, randomized, double-blind, to evaluate efficacy and safety of the fixed-dose combination of Desloratadine 5 mg / Betamethasone 0.25 mg versus Desloratadine 5 mg monotherapy as treatment for symptoms associated with allergic rhinitis.

Nasal symptom changes will be assessed daily over a 10-day intervention period using the Total Nasal Symptom Score (TNSS) for allergic rhinitis. Patients will complete the first questionnaire during the randomization visit, followed by daily entries each night before bedtime using a patient diary. The final assessment will be completed during the study's end-of-treatment visit.

Quality of life, global clinical impression, and patient global assessment will be evaluated during in-person visits conducted at baseline, Day 5, and Day 10.

The incidence of adverse events throughout the study will be analyzed by treatment group and reported as frequencies and percentages. Events will be classified according to frequency, seriousness, severity, and their relationship to the investigational product.

Inclusion Criteria:

• Willing to participate in the study and able to provide written informed consent.
• Clinical diagnosis (based on medical history and physical examination) of active allergic rhinitis at study entry.
• Patients presenting with moderate to severe nasal symptoms, with a Total Nasal Symptom Score (TNSS) ≥5.
• In the case of women of childbearing potential who are sexually active, the use of an acceptable contraceptive method (barrier and/or hormonal), as determined by the investigator.
• In the opinion of the Principal Investigator or treating physician, the patient is indicated for treatment with the investigational product and may derive clinical benefit from it.

Exclusion Criteria:

• Patients for whom the investigational drug is medically contraindicated.
• Known allergy or hypersensitivity to the active ingredient, study medications, related products, or excipients.
• History of nasal trauma (surgical or accidental) within the past week.
• Positive pregnancy test, pregnant or breastfeeding women, or women planning to become pregnant during the course of the study.
• Acute or chronic lower or upper respiratory tract infections, such as the common cold, influenza, pneumonia, bronchitis, or chronic sinusitis.
• History of non-allergic rhinitis, such as chronic non-allergic rhinitis, drug-induced rhinitis, atrophic rhinitis, hormonal rhinitis, or unilateral rhinitis, as reported in the medical history or patient interview.
• History of nasal polyposis, primary ciliary dyskinesia syndrome, and/or non-allergic rhinitis with eosinophilia syndrome (NARES).
• Current smokers, or history of alcohol and/or drug abuse in the past year according to DSM-V criteria.
• History of seizure disorders, status epilepticus, or generalized tonic-clonic seizures.
• History of chronic hepatic failure classified as Child-Pugh C, as reported in the medical history or patient interview.
• History of chronic renal failure (glomerular filtration rate < 30 mL/min/1.73 m²), as reported in the medical history or patient interview.
• Any condition, in the investigator's opinion, that affects prognosis or precludes outpatient management, which must be evaluated by the principal investigator to determine the subject's eligibility.
• History of severe, progressive, unstable, or advanced disease of any kind that could interfere with efficacy and safety evaluations or pose a risk to the patient.
• Oncology patients (except those with basal cell skin cancer) or patients with serious illnesses who, in the investigator's opinion, have a poor prognosis or life expectancy of less than one year, including those with mental health disorders.
• Active participation in another clinical trial involving an investigational treatment or participation in any clinical study within the previous two weeks.
• Patients whose participation in the study may be influenced (e.g., employees of the research center or sponsor, incarcerated individuals, etc.).
• Patients with symptoms suggestive of active COVID-19 infection (e.g., fever, cough, dyspnea) and/or contact within the past 14 days with a suspected or confirmed COVID-19 case and/or a positive COVID-19 test.