• Is a male or female between the ages of 18 and 65 years, inclusive.

• Has been clinically diagnosed with CSU and experiences an acute flare of moderate to severe urticaria symptoms (itch and hive severity UAS score ≥ 2) approximately 1-2 times a month or every other month consistently during the past year while on a chronic treatment.

• Has been on a daily chronic treatment for ≥ 6 weeks.

• Is willing to use a smartphone study application to record study assessments and AEs.

• Has body weight more than 15 kilogram (kg).

• Has no medical history of clinically significant hypertension and cardiovascular disease in the last 10 years

• If female, is not pregnant or breastfeeding based on a negative urine pregnancy test at baseline.

• Is able to communicate clearly with the Investigator and staff; able to read, complete questionnaires, and perform study procedures on the smartphone study application.

• Is willing and able to provide written informed consent prior to participating in the study.

• Controlled hypertension without beta blocker confirmed by the Investigator is acceptable.

• At screening, has stable vital signs in the following ranges (after 5 minutes of rest):

‣ Systolic blood pressure (SBP) ≥90 and ≤140 milliliters of mercury (mmHg)

⁃ Diastolic blood pressure (DBP) ≥50 and ≤90 mmHg

⁃ Heart rate (HR) ≥45 and ≤100 beats per minute (bpm)