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

About this guide

Upper respiratory tract infections (URTIs) — coughs, colds, sore throats, runny noses, and sinusitis — are the single most common reason patients come to our clinic. About 1 in 4 of all primary-care visits at KTMC are for something in this category.

Most URTIs settle on their own in a week or two. But several genuinely useful things are worth knowing:

• How long these normally last (cough of 2–3 weeks after a viral cold is normal)
• Why the colour of your phlegm doesn’t tell us what caused it
• Which cough and cold medicines do what — and which mostly don’t work
• Why we usually don’t prescribe antibiotics (and why that’s a good thing)
• When it’s something more than a cold — pneumonia, strep, bacterial sinusitis
• How to protect yourself and your family in peak viral seasons

This guide is for adults. For children, see Colds, coughs and fevers in children — the approach is different in several important ways.

What is a URTI?

“Upper respiratory tract infection” is an umbrella term for infections affecting the nose, throat, sinuses, voice box, and the upper airways — as opposed to the lungs themselves (pneumonia, bronchitis, etc).

More than 90% of URTIs are caused by viruses. The most common culprits are:

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

Bacterial URTIs are a smaller share and include Group A streptococcal pharyngitis (“strep throat”), some sinusitis, and some otitis media. They often do benefit from antibiotics — but they’re the minority.

Seasonality in Singapore — year-round, but with peaks

Unlike countries with a single winter flu season, Singapore has year-round circulation of multiple respiratory viruses. We see influenza, COVID, RSV, adenovirus, and rhinovirus across the calendar, rather than neatly confined to winter months.

Typical patterns in Singapore:

• Influenza: two loose peaks — around June to August and again around November to January.
• RSV: most active in the wetter months.
• COVID-19: has lost its distinct seasonality but continues to circulate in waves.
• Rhinovirus (common cold): year-round, often rising after school holidays.
• Haze season (typically August–October in bad years) exacerbates respiratory symptoms regardless of the cause.

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

At any given time, several different respiratory viruses are circulating in your neighbourhood. Because we see dozens of patients a week with URTIs and use rapid combined testing (more below), we often have a real-time sense of which viruses are peaking in the area — sometimes days or weeks before national surveillance catches up.

This matters because it informs:

• Whether a specific flu antiviral makes sense for you
• Whether household members should consider prophylactic steps
• Whether your symptoms look more like one pathogen than another (which changes the urgency of testing)

If something is going around in your family or workplace, mention it when you come in — the combination of your history and our local pattern usually points to the likely cause quickly.

The typical timeline of an adult URTI

Most adult URTIs follow a broadly predictable arc:

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

A cough lasting more than 3 weeks should be reviewed (could be post-viral cough, but could also be asthma, post-nasal drip, GORD, whooping cough, or a lower-respiratory cause that deserves assessment).

About the colour of your phlegm

One of the most entrenched beliefs in primary care is “green phlegm means bacterial infection” — and therefore needs antibiotics. It isn’t true, and it doesn’t.

Here’s what actually happens:

• At the start of a URTI, mucus is thin and clear — it’s mostly water with some proteins.
• As your immune system activates, neutrophils (a type of white blood cell) are recruited to the airways. Neutrophils contain an enzyme called myeloperoxidase, which is itself green.
• As mucus becomes more laden with neutrophils, it turns yellow, then green. This is your immune system doing its job.
• The colour reflects how active the inflammation is, not what’s causing it.

Both viral and bacterial URTIs can produce green phlegm. Asthma and bronchiectasis can too. Green sputum on day 5 of a cold is almost always still a normal viral URTI — not a sign it’s “turned bacterial”.

What actually prompts us to consider a bacterial infection is the pattern — persistent high fever beyond 3–5 days, worsening after initial improvement (“double-sickening”), severe localising symptoms, or specific features like chest pain with a cough, or one-sided facial pain with sinusitis. Not the colour.

What actually helps

There isn’t a cure for the common cold. But several things are genuinely helpful:

• Paracetamol or ibuprofen for fever, aches, sore throat, and headache
• Rest — being tired slows recovery; sleep helps immune function
• Fluids — keeps mucus thinner and helps with fever
• Saline nasal sprays or rinses — safe and effective for congestion
• Honey (for adults and children over 12 months) — modest evidence for cough relief, especially at bedtime
• Warm drinks and gargling with warm salty water — symptomatic relief for sore throat
• A humidifier in dry environments (air-conditioned rooms, aircraft) — reduces throat irritation
• Zinc — some modest evidence if started within 24 hours, but side effects (nausea, bad taste) are common

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

The supermarket and pharmacy shelves can be confusing. Broadly, cough and cold medicines fall into a few categories:

Decongestants

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

• Useful for short-term relief of blocked nose from a cold.
• Topical sprays should not be used for more than 3–5 consecutive days (rebound congestion — “rhinitis medicamentosa” — is a real problem).
• Oral pseudoephedrine can raise blood pressure and heart rate; avoid in uncontrolled hypertension, some cardiac conditions, pregnancy.

Mucolytics

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

• Thin mucus so it’s easier to clear.
• Evidence for benefit in uncomplicated adult URTI is modest.
• Most are available over the counter in Singapore pharmacies.
• Reasonable to try if you feel your chest is congested and productive; not essential.

Expectorants

Guaifenesin (in many combined cough syrups).

• Intended to help loosen and cough up secretions.
• Evidence for efficacy is limited and inconsistent.
• Adequate fluid intake does roughly the same thing for free.

Cough suppressants (antitussives)

Dextromethorphan (e.g. DM in many cough syrups), codeine, pholcodine.

• Reduce the cough reflex. Useful for dry, non-productive cough that’s disturbing sleep or work.
• Dextromethorphan is the main OTC option in Singapore.
• Codeine and pholcodine are prescription-only in Singapore. Because of variable individual metabolism (some people convert codeine to morphine very rapidly), we’re cautious about codeine even in adults.
• Not to be used to suppress a productive, phlegmy cough — that cough is usually helpful.

Antihistamines

First-generation (chlorpheniramine, diphenhydramine) — sedating, help with runny nose and cough at night, can cause drowsiness and dry mouth.

Second-generation (loratadine, cetirizine, fexofenadine) — non-sedating, more useful for allergic rhinitis than viral colds, but often included in cold preparations.

Flu-specific antivirals

Oseltamivir (Tamiflu) — works against influenza only.

• Works best if started within 48 hours of symptom onset — reduces illness duration by about a day on average, and reduces complications (pneumonia, hospitalisation) more substantially in high-risk groups.
• Greatest benefit in:
  • Older adults (65+)
  • Pregnancy
  • Chronic conditions (asthma, COPD, heart disease, diabetes, CKD, immunocompromise)
  • Severe or deteriorating illness
• Can be given prescriptively to a household contact of a confirmed flu case who is at high risk — reduces their chance of catching it.

In Singapore, oseltamivir is prescription-only and dispensed based on symptoms plus, where available, a positive flu test.

What’s over the counter vs prescription in Singapore

As a rough rule:

• Over the counter at pharmacies: paracetamol, ibuprofen, saline sprays, dextromethorphan, guaifenesin, loratadine/cetirizine, bromhexine, pseudoephedrine, topical decongestant sprays, lozenges.
• Prescription-only: codeine, pholcodine, oseltamivir (Tamiflu), strong pseudoephedrine combinations in some cases, nebuliser medications, most antibiotics.

Pharmacists at any major Singapore pharmacy can give excellent guidance on OTC combinations. If unsure — particularly if you’re on medications for other conditions — ask them or us.

What usually doesn’t help (and can harm)

Antibiotics for viral URTI

This is the biggest one. Antibiotics do not work against viruses, and the vast majority of coughs, colds, sore throats, and sinusitis episodes in adults are viral. Taking antibiotics for a viral infection:

• Won’t shorten the illness — a dozen large trials confirm this
• Won’t prevent progression to a bacterial complication
• Can cause harm — rash, diarrhoea (including Clostridioides difficile colitis in severe cases), yeast infections, allergic reactions, interactions with other medications
• Contributes to antibiotic resistance — bacteria around you (and in your gut) develop resistance every time antibiotics are used unnecessarily, making future real infections harder to treat

When we don’t prescribe antibiotics for your cold, cough, or green phlegm — it’s not because we’re being stingy. It’s because it’s the right call. If your symptoms suggest a bacterial cause, we’ll prescribe appropriately; if they don’t, the best prescription is rest, paracetamol, fluids, and time.

Most advertised “immune boosters”

Vitamin C, echinacea, elderberry, and a long list of marketed supplements have inconsistent or negative evidence for preventing or treating colds. Adequate zinc, vitamin D, sleep, and nutrition in general help, but megadose supplements during an active illness don’t.

Sore throat — is it strep?

Most sore throats in adults are viral and settle with paracetamol, warm drinks, and rest. Group A streptococcal (“strep”) pharyngitis is a smaller share but is worth identifying — untreated strep carries a small risk of rheumatic fever and post-streptococcal glomerulonephritis.

Features that raise the probability of strep (the Centor criteria):

• Fever (usually above 38°C)
• Tonsillar exudate (white or yellow spots on the tonsils)
• Tender enlarged lymph nodes in the front of the neck
• Absence of cough (strep usually doesn’t cause cough)

The more of these you have, the more likely it’s strep. We often use a rapid antigen strep test in clinic — a quick throat swab — to help confirm and decide on antibiotics. A negative test with a classic clinical picture may occasionally prompt a confirmatory throat culture.

If you just have a sore throat with a runny nose and a cough, it’s 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 possible but is a minority.

Features that make us consider bacterial sinusitis:

• Symptoms persisting for more than 10 days without improvement
• “Double-sickening” — initial improvement followed by worsening
• Severe unilateral facial pain and pressure
• High fever with purulent nasal discharge and facial pain

If you have the classic viral-cold picture for a week, a saline rinse and time is usually the right treatment. Come in if you meet the bacterial pattern above, or if symptoms are progressively worse.

When a cough isn’t URTI

Cough has many causes besides an acute viral illness. If your cough is lasting more than 3 weeks or doesn’t fit the URTI pattern, think about:

• Asthma — cough, wheeze, breathlessness, triggers, night symptoms; see our adult asthma guide
• Post-nasal drip / allergic rhinitis — often with a tickle at the back of the throat, worse in the morning
• Gastro-oesophageal reflux — particularly a cough that’s worse lying down after meals
• ACE inhibitor side effect — a dry cough in a patient on perindopril, enalapril, ramipril, etc. is often the culprit; tell us if this applies
• Smoking / vaping
• Pneumonia or lower-respiratory infection — productive cough with fever, breathlessness, chest pain
• Tuberculosis — a cough lasting weeks with weight loss, night sweats, fever
• Whooping cough (pertussis) — a prolonged, paroxysmal cough, often with post-coughing vomiting; can happen in vaccinated adults whose immunity has waned
• Lung cancer — rare but worth considering in smokers, older patients, or with red flags like blood in the sputum, weight loss

If a cough isn’t settling, come in. The history usually narrows it quickly.

Testing — what’s available at the GP

Not every URTI needs a test. For straightforward cases, a clinical assessment is usually enough. Testing helps us when:

• The patient is high-risk (older, chronic disease, immunocompromised, pregnant) and the result would change treatment (e.g. oseltamivir for influenza)
• There’s a household outbreak and identifying the pathogen informs household management
• Symptoms are severe or progressing atypically
• Household members need to make decisions about isolation, childcare, work

What’s typically available at KTMC:

• Rapid antigen tests (RAT) — single pathogen 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. These have improved substantially in sensitivity and are useful at the point of care.
• Rapid antigen strep test — a throat swab, 15 minutes, for strep pharyngitis
• Respiratory PCR panels — a more sensitive and broader test (often 20+ pathogens). Available at the GP setting at a cost — we send the sample to a lab and results usually come back within a day. Used when a definitive diagnosis is important.

When to come in

Book a visit (or come urgently) if:

• You’re high-risk and suspect flu or COVID (especially within 48 hours of onset)
• Fever above 38.5°C lasting more than 3 days, or returning after settling
• Shortness of breath at rest, chest pain, or unusual fatigue
• Cough with blood
• Severe one-sided facial pain (possible sinusitis)
• Severe sore throat with fever, difficulty swallowing fluids, or one-sided swelling (consider quinsy or strep)
• Cough lasting more than 3 weeks
• Not improving after 7–10 days, or worsening after an initial improvement (double-sickening)
• You have chronic asthma, COPD, heart disease, diabetes, or immunocompromise and have caught something respiratory — we often want to review early rather than waiting for trouble

Red flags warranting 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 single biggest preventive measure is annual influenza vaccination. Others with strong evidence:

• COVID-19 boosters as recommended for your age group and risk profile
• Pneumococcal vaccination (one-off or episodic, depending on the schedule) — particularly for adults 65+ or those with chronic conditions
• RSV vaccines are now available for adults 60+ and specific other groups
• Hand hygiene — the single biggest modifiable protective factor; wash with soap and water or use an alcohol-based sanitiser
• Masks in crowded enclosed spaces during known peaks (peak flu weeks, known outbreak in your building/school), particularly if you’re at higher risk or caring for someone vulnerable
• Adequate sleep, nutrition, and hydration — measurable effects on immune function
• Staying home when unwell — both to recover and to reduce spread

Protecting your family when you’re unwell

When you’ve got a URTI, a few simple steps dramatically reduce household spread:

• Wear a mask at home when you’re in close contact with family members
• Sleep separately if practical, especially if sharing with a higher-risk family member (elderly parent, pregnant partner, young infant)
• Cover your mouth with your elbow or a tissue when coughing; dispose of tissues straight away and wash hands
• Don’t share cups, utensils, towels
• Clean high-touch surfaces — door handles, phones, remote controls
• Ventilate indoor spaces — open a window if possible
• If you test positive for flu and a household member is high-risk (pregnant, elderly with chronic disease, infant, immunocompromised), we can discuss prophylactic oseltamivir for that contact

Once you’re fever-free for 24 hours without paracetamol and feeling better, most activities can resume — though any cough or runny nose remains modestly contagious for another few days.

Return to work

Most healthy adults return to work once fever and major symptoms have settled — typically 3 to 5 days after onset for a routine viral URTI. MCs (medical certificates) are issued based on clinical need, not on request for a specific duration. If you’re in a customer-facing or healthcare-adjacent role, staying home until the cough and congestion substantially improve is sensible.

Cross-links

• Children with URTI — what parents need to know — different principles, different medications
• Beyond the Jab: Navigating Flu Season in Singapore — the flu-specific companion piece
• Asthma — what it is, and how we treat it today — if your “persistent cough” isn’t settling

Get in touch

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

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

Email — admin@ktmc.sg

References

Clinical guidance

• Agency for Care Effectiveness (ACE). Upper respiratory tract infection. ACE Clinical Guidance (draft for professional bodies review). 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.
• 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. v1.0 · April 2026 · Review due April 2028.