The goal of this clinical trial is to assess and compare the effect of ebastine and placebo in improving symptoms in patients with diarrhea predominant IBS. It will also assess about the safety of drugs ebastine and placebo by recording the patient reported adverse events. The main questions it aim to answer are: Does drug ebastine and placebo has any effect on patients with IBS-D? What medical problems do participants have when taking drug ebastine and placebo? Researcher will compare effect of drug ebastine and placebo . Participant will: Take drug ebastine 20 mg at night and placebo once daily at night every day for 8 weeks along with lifestyle modifications. After that all two groups will visit the hospital 4 weekly, and their symptoms will be assessed by IBS symptom severity score (IBS-SSS) at baseline, week 4 and week 8. Additionally, patient reported adverse events will be documented.