Colds, coughs, sore throats and sinusitis — what helps, what doesn't, and when to see us

In brief

• Most colds, coughs and sore throats are viral and settle on their own, though a cough can last 2 to 3 weeks.
• Green or yellow phlegm does not mean a bacterial infection or a need for antibiotics.
• Paracetamol or ibuprofen, rest, fluids, saline sprays and honey help; antibiotics do not work against viruses.
• Flu antivirals work best when started within 48 hours, especially in people at high risk.
• See a doctor for fever above 38.5°C lasting more than 3 days, a cough beyond 3 weeks, coughing up blood, or worsening after initial improvement.
• Go to A&E for severe breathlessness, blue lips, confusion or chest pain.

We assess coughs, colds and sore throats at our Punggol clinic, with rapid tests where useful. Book an appointment.

What is a URTI?

An upper respiratory tract infection (URTI) affects the nose, throat, sinuses, voice box or upper airways, rather than the lungs (pneumonia, bronchitis). URTIs account for about 1 in 4 of our primary-care visits, more than any other reason. Most settle on their own in a week or two.

This guide is for adults. Children need a different approach; see Colds, coughs and fevers in children.

More than 90% of URTIs are caused by viruses, most often:

• Rhinoviruses, the main common-cold viruses, with over 100 strains
• Coronaviruses (seasonal ones and SARS-CoV-2)
• Respiratory syncytial virus (RSV)
• Influenza A and B (“flu”)
• Parainfluenza (especially in croup)
• Adenoviruses, which often cause sore throat with fever
• Metapneumovirus and enteroviruses

Bacterial URTIs, the minority, include Group A streptococcal pharyngitis (“strep throat”), some sinusitis and some middle-ear infections (otitis media). These often do benefit from antibiotics.

Seasonality in Singapore — year-round, but with peaks

Singapore has no single flu season. Influenza, COVID, RSV, adenovirus and rhinovirus circulate year-round, with these patterns:

• Influenza: two loose peaks, around June to August and November to January.
• RSV: most active in the wetter months.
• COVID-19: no distinct season, but continues in waves.
• Rhinovirus (common cold): year-round, often rising after school holidays.
• Haze season (typically August–October in bad years) worsens respiratory symptoms whatever the cause.

Why the GP you see regularly often knows what’s going around

We see dozens of patients with URTIs each week and use rapid combined tests (see below). So we often know which viruses are peaking locally, sometimes days or weeks before national surveillance catches up. That helps us decide on flu antivirals, preventive steps for your household, and how urgently to test. Tell us if something is going around your family or workplace.

The typical timeline of an adult URTI

You are most infectious in the first 2–3 days, often before you feel your worst.

Have a cough lasting more than 3 weeks reviewed. It may be post-viral, or asthma, post-nasal drip, GORD, whooping cough or a lower-respiratory cause.

About the colour of your phlegm

Many people believe green phlegm means a bacterial infection that needs antibiotics. It doesn’t.

• Early in a URTI, mucus is thin and clear, mostly water with some proteins.
• As your immune system responds, neutrophils (white blood cells) move into the airways. They contain an enzyme, myeloperoxidase, that is itself green.
• As neutrophils build up, mucus turns yellow, then green. This is your immune system at work.

The colour reflects how active the inflammation is, not what caused it. Viral and bacterial URTIs both produce green phlegm, as can bronchiectasis or severe flares of chronic lung disease. Green phlegm on day 5 of a cold is almost always still a normal viral URTI.

What makes us consider bacterial infection is the pattern: high fever persisting beyond 3–5 days, worsening after initial improvement (“double-sickening”), severe localised symptoms, chest pain with a cough, or one-sided facial pain with sinusitis.

What actually helps

There is no cure for a cold, but these help:

• Paracetamol or ibuprofen for fever, aches, sore throat and headache.
• Rest. Tiredness slows recovery, and sleep helps immune function.
• Fluids keep mucus thinner and help with fever.
• Saline nasal sprays or rinses safely ease congestion.
• Honey (adults and children over 12 months) has modest evidence for easing cough, especially at bedtime.
• Warm drinks and warm salt-water gargles soothe a sore throat.
• A humidifier in dry air (air-conditioned rooms, aircraft) reduces throat irritation.

Cough, cold, and flu medications — a short guide to what does what

Decongestants

Pseudoephedrine (e.g. in Clarinase-D, Sudafed) and topical decongestant sprays (oxymetazoline, xylometazoline).

• They briefly relieve a blocked nose from a cold.
• Don’t use the sprays for more than 3–5 consecutive days, because of rebound congestion (rhinitis medicamentosa).
• Oral pseudoephedrine can raise blood pressure and heart rate. Avoid it with uncontrolled high blood pressure, some heart conditions, and in pregnancy.

Mucolytics

Bromhexine, ambroxol, carbocisteine, acetylcysteine (e.g. Fluimucil).

They thin mucus so it is easier to clear. Evidence of benefit in uncomplicated adult URTI is modest. Try them if your chest feels congested and productive, but they are not essential.

Expectorants

Guaifenesin (in many combined cough syrups) is meant to loosen secretions. Evidence is limited and inconsistent, and drinking enough fluid does roughly the same for free.

Ivy leaf extract (herbal)

Dried ivy leaf extract (e.g. Prospan), sold in Singapore pharmacies, shows modest symptom benefit for cough in randomised trials, particularly productive cough. It is well tolerated and widely used in Europe, and increasingly in Singapore. It is a reasonable single-ingredient alternative to “combo” cough syrups.

Cough suppressants (antitussives)

Dextromethorphan (in many combined cough syrups), codeine.

• They reduce the cough reflex, which helps a dry cough that disturbs sleep or work.
• In Singapore, dextromethorphan products are pharmacy-classified: sold at pharmacies, often with pharmacist input, not on supermarket shelves.
• Codeine is prescription-only. Some people turn it into morphine very rapidly, which can dangerously slow breathing, so we use it cautiously even in adults.
• Pholcodine was withdrawn from Singapore in June 2023 (HSA). Past use was linked to a higher risk of severe allergic reactions to muscle relaxants used in general anaesthesia. Discard any old pholcodine syrup.
• Don’t suppress a productive, phlegmy cough. It is usually clearing something your body wants out.

Antihistamines

First-generation antihistamines (chlorpheniramine, diphenhydramine) are sedating, and their anticholinergic effects can reduce a runny nose and post-nasal drip. They appear in many “night-time” cold remedies, causing drowsiness, dry mouth and poor concentration.

Second-generation (loratadine, cetirizine, fexofenadine) antihistamines are non-sedating and were developed mainly for allergic rhinitis, not colds.

A Cochrane review (De Sutter et al. 2015) found antihistamines alone had no clinically significant effect on blocked nose, runny nose or sneezing in colds. In combination products, they had only a modest short-term effect on overall symptoms. They help when there is an allergic component, but are not a reliable add-on for a plain viral cold.

Flu-specific antivirals

Two prescription-only antivirals are used for influenza in Singapore.

Oseltamivir (Tamiflu) is an oral capsule taken twice daily for 5 days, active against influenza A and B.

• It works best if started within 48 hours of symptom onset. It shortens illness by about a day on average, and cuts complications (pneumonia, hospital admission) more in high-risk groups.
• Greatest benefit in:
  • Older adults (65+)
  • Pregnancy
  • Chronic conditions (asthma, COPD, heart disease, diabetes, CKD, weakened immunity)
  • Severe or worsening illness
  • High-risk children (under 2, or with asthma, congenital heart disease or weakened immunity); see our children’s URTI guide
• It can be given to a high-risk household contact of a confirmed case, to reduce their chance of catching flu.

Baloxavir (Xofluza) is a newer oral antiviral, given as a single dose.

• It targets a different part of the flu virus (a cap-dependent endonuclease), useful if oseltamivir resistance is a concern or 5 days of twice-daily doses is hard to manage.
• It rapidly reduces viral shedding. In a large 2025 trial, household members of people given baloxavir caught flu less often than those of people given a placebo (9.5% vs 13.4% by day 5), though the drop in infections causing symptoms was not statistically significant. The trial did not compare it with oseltamivir. This may matter in households with vulnerable members.
• It also works best within 48 hours of onset.
• Availability and cost vary; we can discuss which suits you.

We usually prescribe either after a positive flu test, or on strong suspicion when flu is circulating.

What’s available without a prescription in Singapore

Singapore has three tiers of medicine. For cold and cough products, roughly:

• General Sale, freely available in supermarkets, convenience stores and pharmacies: paracetamol, ibuprofen, saline nasal sprays, most lozenges.
• Pharmacy-classified, sold at pharmacies without a prescription: guaifenesin, loratadine, cetirizine, bromhexine, ambroxol, carbocisteine, acetylcysteine (Fluimucil), ivy leaf extract (Prospan), pseudoephedrine, topical decongestant sprays, dextromethorphan-containing cough products.
• Prescription-only: codeine-containing cough medicines, oseltamivir (Tamiflu), baloxavir (Xofluza), most antibiotics, nebuliser medicines.

If you take regular medicines, check with us before buying a combination cold remedy. Pseudoephedrine especially interacts with blood-pressure medicines, some antidepressants and certain heart medicines.

What usually doesn’t help (and can harm)

Antibiotics — a shared decision

We decide together whether antibiotics are right for you, based on your symptoms and examination.

Antibiotics do not work against viruses, and most adult coughs, colds, sore throats and sinusitis are viral. For these, antibiotics:

• Do not shorten the illness, as many randomised trials confirm.
• Do not prevent progression to a bacterial complication.
• Can cause harm: rash, diarrhoea (including Clostridioides difficile colitis in severe cases), yeast infections, allergic reactions and drug interactions.
• Add to antibiotic resistance, in bacteria around you and in your gut, making future real infections harder to treat.

If features suggest a bacterial cause (high fever beyond 3–5 days, worsening after initial improvement, clear strep features, severe localised sinus pain and tenderness, or signs of pneumonia), we discuss which antibiotic, for how long, and what to watch for. Otherwise we explain what will help instead, usually rest, paracetamol, fluids and time. Please raise any concerns, so you understand and are comfortable with the decision.

“Immune boosters” — a conversation worth having

Many people take immune boosters such as high-dose vitamin C, echinacea, elderberry, or herbal and multivitamin mixes. A few specific preparations and doses show modest benefit, most don’t, and contents vary widely between brands.

We would rather talk it through with you than judge them all at once. Bring the bottle, or a photo of the label, and we can review the evidence, interactions with your medicines, and the cost. Simpler measures may do more: enough sleep, decent nutrition, fluids and an annual flu vaccination.

Please don’t stop prescribed medicines for unregulated supplements. If you are considering it, raise it at a visit so we can plan together.

Sore throat — is it strep?

Most adult sore throats are viral and settle with paracetamol, warm drinks and rest. Group A streptococcal (“strep”) pharyngitis is less common but worth finding, as untreated strep carries a small risk of rheumatic fever and post-streptococcal glomerulonephritis.

Features that make strep more likely (the Centor criteria):

• Fever, usually above 38°C
• Tonsillar exudate (white or yellow spots on the tonsils)
• Tender, enlarged lymph nodes at the front of the neck
• No cough (strep usually doesn’t cause one)

The more of these you have, the likelier strep is. A rapid antigen strep test (a quick throat swab) helps us confirm it and decide on antibiotics. If it is negative but the picture is classic, we may occasionally send a throat culture.

A sore throat with a runny nose and a cough is almost always viral, and antibiotics won’t help.

Sinusitis — viral versus bacterial

Most “sinus infections” are viral, effectively a cold with facial congestion. Bacterial sinusitis is the minority. We consider it with:

• Symptoms lasting more than 10 days without improvement
• “Double-sickening”: initial improvement, then worsening
• Severe one-sided facial pain and pressure
• High fever with purulent nasal discharge and facial pain

For a typical week-long cold, saline rinses and time usually suffice. Come in if you fit the bacterial pattern or are steadily worsening.

When a cough isn’t URTI

If a cough lasts more than 3 weeks or doesn’t fit the URTI pattern, consider:

• Asthma: cough, wheeze, breathlessness, triggers, night symptoms; see our adult asthma guide
• Post-nasal drip / allergic rhinitis: often a tickle at the back of the throat, worse in the morning
• Gastro-oesophageal reflux: especially a cough worse lying down after meals
• ACE inhibitors: a dry cough on perindopril, enalapril, ramipril and similar drugs
• Smoking or vaping
• Pneumonia or other lower-respiratory infection: productive cough with fever, breathlessness, chest pain
• Tuberculosis: a cough lasting weeks with weight loss, night sweats, fever
• Whooping cough (pertussis): prolonged coughing fits, often followed by vomiting; it can occur in vaccinated adults whose immunity has waned
• Lung cancer: rare, but considered in smokers, older people, or with blood in the sputum or weight loss

If a cough isn’t settling, come in.

Testing — what’s available at the GP

Straightforward URTIs don’t need a test. Testing helps when:

• You are high-risk (older, chronic disease, weakened immunity, pregnant) and the result would change treatment, e.g. oseltamivir for flu.
• There is a household outbreak, and knowing the cause guides isolation, childcare or work decisions.
• Symptoms are severe or progressing unusually.

Typically available at KTMC:

• Rapid antigen tests (RAT): single-pathogen tests or 5-in-1 combined panels that detect COVID-19, influenza A and B, RSV and adenovirus from one nasal swab in about 15 minutes. Their sensitivity has improved substantially.
• Rapid antigen strep test: a throat swab, with results in 15 minutes.
• Respiratory PCR panels: more sensitive and broader, often covering 20+ pathogens, at a cost. A lab processes the sample, usually within a day. We use it when a definite diagnosis is important.

When to come in

Book a visit, or come urgently, if:

• You are high-risk and suspect flu or COVID, especially within 48 hours of onset
• Fever above 38.5°C lasts more than 3 days, or returns after settling
• You are short of breath at rest, or have chest pain or unusual fatigue
• You cough up blood
• You have severe one-sided facial pain (possible sinusitis)
• You have a severe sore throat with fever, difficulty swallowing fluids or one-sided swelling (possible quinsy or strep)
• A cough lasts more than 3 weeks
• You are not improving after 7–10 days, or are worsening after initial improvement (double-sickening)
• You have chronic asthma, COPD, heart disease, diabetes or weakened immunity and catch a respiratory infection; we often prefer to see you early

Red flags needing A&E:

• Severe breathlessness (can’t complete a sentence)
• Blue lips or fingertips
• Confusion or reduced responsiveness
• Chest pain
• A sudden severe illness in a high-risk person

Protecting yourself in peak seasons

The most important preventive measure is annual influenza vaccination. Others with strong evidence:

• COVID-19 boosters as recommended for your age and risk.
• Pneumococcal vaccination (one-off or repeated, depending on the schedule), particularly for adults 65+ or with chronic conditions.
• RSV vaccines, now available for adults 60+ and some other groups.
• Hand hygiene with soap and water or an alcohol-based sanitiser, the biggest protective factor within your control.
• Masks in crowded indoor spaces during peak flu weeks or local outbreaks, especially if you or someone you care for is higher-risk.
• Enough sleep, nutrition and fluids, which measurably affect immune function.
• Staying home when unwell, to recover and to reduce spread.

Protecting your family when you’re unwell

Simple steps greatly reduce household spread:

• Wear a mask at home when in close contact with family.
• Sleep apart if practical, especially from a higher-risk family member (elderly parent, pregnant partner, young baby).
• Cough into your elbow or a tissue, bin tissues at once and wash your hands.
• Don’t share cups, utensils or towels.
• Clean high-touch surfaces such as door handles, phones and remote controls.
• Open a window to ventilate if possible.
• If you test positive for flu and a household member is high-risk (pregnant, elderly with chronic disease, an infant, weakened immunity), ask us about prophylactic (preventive) oseltamivir for them.

Once you have been fever-free for 24 hours without paracetamol and feel better, most activities can resume, though a cough or runny nose stays mildly contagious for a few more days.

Return to work

Most healthy adults return to work once fever and major symptoms settle, typically 3 to 5 days after onset of a routine viral URTI. We issue medical certificates (MCs) on clinical need, not requests for a set duration. In customer-facing or healthcare-related roles, stay home until cough and congestion are much better.

Cross-links

• Children with URTI — what parents need to know
• Beyond the Jab: Navigating Flu Season in Singapore, on flu
• Asthma — what it is, and how we treat it today, for a persistent cough

Get in touch

Punggol — 658 Punggol East, #01-04, Singapore 820658 · Tel 6312 4589

Joo Chiat — 172 Joo Chiat Road, #01-01, Singapore 427443 · Tel 6920 1952

Email — admin@ktmc.sg

References

Clinical guidance

• Agency for Care Effectiveness (ACE). Upper respiratory tract infections — rational antimicrobial use. ACE Clinical Guideline, Ministry of Health, Singapore. May 2026. ace-hta.gov.sg
• Health Sciences Authority Singapore. Cough and cold medicines — what you should know. hsa.gov.sg
• Health Promotion Board Singapore / MOH. Seasonal influenza surveillance; National Adult Immunisation Schedule (NAIS). healthhub.sg

Specific evidence

• Stolz D, Christ-Crain M, Gencay MM, et al. Diagnostic value of signs, symptoms and laboratory values in lower respiratory tract infection. Swiss Med Wkly. 2006;136:434-440 — on sputum colour and bacterial infection.
• Smith SM, Schroeder K, Fahey T. Over-the-counter (OTC) medications for acute cough in children and adults in community settings. Cochrane Database Syst Rev. 2014;(11):CD001831 — limited evidence for most OTC cough products.
• Jefferson T, Jones MA, Doshi P, et al. Neuraminidase inhibitors for preventing and treating influenza in adults and children. Cochrane Database Syst Rev. 2014;(4):CD008965 — oseltamivir efficacy and caveats.
• Monto AS, Kuhlbusch K, Bernasconi C, et al. Efficacy of baloxavir treatment in preventing transmission of influenza. N Engl J Med. 2025;392(16):1582–1593 — CENTERSTONE trial: single-dose baloxavir vs placebo in index patients; household transmission by day 5 9.5% vs 13.4%; symptomatic transmission difference not significant. nejm.org
• Centor RM, et al. Centor criteria for streptococcal pharyngitis — original description and subsequent validations.

This information is for general education only and is not a substitute for medical advice. If you’re unwell, please speak with our team about what’s right for you. v1.1 · October 2026 (v1.0 April 2026) · Review due April 2028.