Flu or a Common Cold? How to Tell the Difference in Your Child

Your child was fine this morning — and by the evening they're in bed with a burning forehead and the shivers. That sudden change is the single most useful clue that tells real flu apart from an ordinary cold. The reassuring part: even flu usually passes without complications in otherwise healthy children. Here's how to tell the difference — and which warning signs really matter.

Flu or a common cold — what's the difference?

They sound similar but mean two different things. Real flu (influenza) is caused by flu viruses and can be a serious illness. A common cold is caused by other viruses and is usually mild. In everyday language the two get mixed up all the time.

The distinction matters: flu tends to be more severe, with a high temperature and symptoms that come on quickly, while a cold develops gradually and runs a benign course. In practice, the give-away is how fast and how hard it hits. Flu floods in within hours and leaves your child feeling wiped out; a cold builds slowly over a few days and your child usually stays reasonably active.

How do I recognise real flu in my child?

Flu typically starts suddenly. The tell-tale signs are a sudden high temperature, a dry cough, aches and pains, headache, and a child who feels weak, very tired and properly unwell — not just a bit snuffly. A high temperature in the UK usually means around 38°C or above. The speed and severity are what set flu apart from a cold.

In children the picture can include a few extras. As well as the usual cold-like symptoms, children with flu may have a fever, sore muscles, a sore throat, ear pain and simply appear less active than usual. Younger children sometimes also get tummy upset such as nausea or being sick.

How do the symptoms compare?

The onset and the intensity tell you most of what you need to know. Flu arrives suddenly with a high temperature and a child who feels floored; a cold creeps in over a couple of days, stays milder, and your child carries on more or less as normal. The table below sums up the typical differences.

This is a guide, not a diagnosis. The two overlap, and small children rarely follow the textbook. If your child seems very unwell or isn't improving, let a healthcare professional make the call rather than your gut feeling.

When is it an emergency? Which warning signs need a doctor straight away?

Most children get through flu at home. But some warning signs mean you shouldn't wait — breathing problems, a child who stays very unwell, signs of dehydration, or any clear deterioration. When in doubt, it's better to call early than too late.

If you're unsure whether a symptom is harmless, that uncertainty is itself a good enough reason to call NHS 111 or your GP. For more detail on fever, see our guide Fever in children: when is it dangerous?.

How long does flu last in children — and what helps?

Flu symptoms come on very quickly, and in otherwise healthy children they usually ease within a week or two — though a cough and tiredness can linger for longer. A common cold also tends to clear up within 1 to 2 weeks. Both can only be treated to ease the symptoms — there's no quick fix that clears the virus itself.

What helps most now is rest, plenty of fluids and patience. You don't have to bring a temperature down at all costs; what matters is how your child is in themselves. If you give a medicine for fever or pain, follow the package leaflet and ask your pharmacist or GP if you're unsure — the right choice and dose depend on your child's age and weight.

For a closer look at children's fever medicines, see Ibuprofen or paracetamol for my child?.

Frequently asked questions about flu and colds in children

Can I reliably tell flu and a cold apart myself?

Not always. A sudden onset, a high temperature and a child who is properly unwell point towards flu; a gradual start with a runny nose points towards a cold. But the two overlap, and only a GP — sometimes with a test — can be sure. When in doubt, go by how unwell your child seems rather than the label.

What counts as a high temperature?

In the UK, a high temperature is usually considered to be around 38°C or above. With flu it often comes on suddenly. The number alone isn't everything, though: how your child is behaving — whether they're drinking, alert and able to be comforted — tells you at least as much as the thermometer.

How long is my child contagious with flu?

Children can spread flu viruses from shortly before symptoms start and then for several days — often longer than adults. As a rule, while your child has a temperature and feels unwell, treat them as contagious. Good hygiene and keeping them away from other children during this time reduce the risk of passing it on.

When can my child go back to nursery after flu?

There's no fixed number of days. As a rule of thumb, your child should be back to normal in themselves and no longer have a temperature before returning. Check your nursery's own policy too, and ask your GP if you're unsure whether your child is well enough.

Do antibiotics help with flu?

No. Flu is caused by viruses, and antibiotics don't work against viruses. They're only relevant if a bacterial complication develops on top of the flu, such as an ear or chest infection — and that's a decision for your GP, not the medicine cabinet.

Should I get my child a flu vaccine?

A yearly flu vaccine can be worthwhile, and in the UK it's offered to many children. Whether and from what age it's recommended for your child is best discussed with your GP or practice nurse, who can advise based on your child's age and health.

Summary: flu or a cold — what to do?

Flu or cold, the same thing helps: if you jot down the temperature readings, any medicine you've given and how your child is doing, you'll spot a deterioration sooner — and can tell your GP exactly what happened and when. Mona makes this easy: the fever curve shows the trend at a glance, and the medication log records every dose with the time.