Warming Sensation and Tolerability Study of Acetylcysteine 2% Oral Solution for Productive Cough

Inclusion Criteria: * Participants must give written informed consent before any assessment is performed. In the case of adolescents Informed Consent must be signed by one or both parents or legal guardian as per local regulations and an Informed Assent must be signed by the participant. * Must be males or females ≥ 12 years. * Willingness and ability to communicate, to comply with all study requirements and to complete the study. * Productive cough of less than 7 days duration, rated based on interview with the participant as mild to moderate severity on a four- point ordinal scale (not present, mild, moderate, severe) due to upper respiratory tract infection. Exclusion Criteria: * Use of other investigational drugs before enrollment, or within 30 days or 5 half-lives before enrollment, whichever is longer. * Pre-dose productive cough or sore throat rated as severe on a four-point ordinal scale (not present, mild, moderate, severe) based on interview with the participant. * Pre-dose temperature equal or above 39.4°C at screening measured by oral thermometer. * History of hypersensitivity to any of the study drugs and the listed excipients or to drugs of similar chemical classes. * Pregnant , nursing (lactating women) or women with child bearing potential UNLESS they are using effective methods of contraception. * Use of any medication for sore throat containing a local anaesthetic, methanol or any topical products containing menthol, peppermint, spearmint or within the 6 hours prior to dosing. * Use of any paracetamol, non-steroidal anti-inflammatory drug (NSAID) or any oral/nasal decongestant within 6 hours prior to dosing. * Use of substances of abuse, herbal medications, or antihistamines within 48 hours of dosing. * Hepatic or severe renal impairment, hypertension, hyperthyroidism, diabetes, or heart disease. * Drinking of tea, coffee or other caffeinated beverages 1 hour prior to dosing. * Drinking of any hot beverages 1 hour prior to dosing. * Participant is a current smoker of ≥10 cigarettes per day (or reports equivalent smoking habits using other tobacco products) or smoked or chewed tobacco products within 12 hours before dosing. * Participant is taking nitroglycerin and nitrate drug treatments. * Participants who took antibiotic treatments such as semisynthetic penicillins, tetracyclines, cephalosporins and aminoglycosides within 2 hours of dosing. Amoxicillin, doxycycline, erythromycin, thiamphenicol and cefuroxime are allowed without this restriction. * Participants with gastroduodenal (peptic) ulcers, asthma. * Participants with intolerance to histamines. * Participants who have used antitussives (e.g., dextromethorphan, codeine), anticholinergic drugs (atropine-like) within the past 24 hours. * Participants who have taken heavy metal salts such as calcium, gold and iron within 2 hours of enrollment. * A history of alcohol abuse or an admission by the participant that they regularly consume alcohol in excess of the recommended weekly limits of 21 units for females and 28 units for males. * History of malignancy of any organ system (other than localized basal cell carcinoma of the skin), treated or untreated, within the past 5 years, regardless of whether there is evidence of local recurrence or metastases.