The study will conduct with 4 comparative groups orally treated with YHD001 dose level 1(t.i.d.), YHD001 dose level 2(t.i.d.), pelargonium sidoides extract 9mL(t.i.d.) or Placebo for 7 days.

The treatments will be assigned randomly to patients (n=116) with acute or chronic bronchitis.

The outcome measures is to evaluate the overall change from baseline to the end of treatment in scores relating to the severity of four symptom of bronchitis: cough, sputum, QOL of daily life, QOL of falling asleep at night.

Inclusion Criteria:

• Male and female patients aged ≥18 year
• Provision of written informed consent
• Acute bronchitis with a Bronchitis Severity Score(BSS)≥five points

Exclusion Criteria:

• History of any clinically significant disease
• History of drug/chemical/alcohol abuse
• Use of antibiotics, anti-histamine during the 7 days before administration of the investigational product