Colds and flu explained
Colds and flu are both caused by viruses that infect the upper respiratory tract — the nose, throat and airways. The common cold can be caused by many different viruses, while flu (influenza) is caused by influenza viruses. Although they overlap, they are different illnesses, and flu tends to be considerably more severe than a cold.
Both are spread easily from person to person, through droplets when an infected person coughs or sneezes, and by touching contaminated surfaces then touching the face. They are most common in the colder months. Most people recover from both without complications, but flu in particular can be more serious for certain groups, which is why understanding the difference matters.
Telling a cold from flu
While colds and flu share symptoms, some differences help tell them apart. Flu typically comes on suddenly and makes you feel exhausted and unwell all over, while a cold develops more gradually and mainly affects the nose and throat. Key differences include:
- •Onset: flu comes on suddenly; colds develop gradually
- •Fever: common and often higher with flu; rare or mild with a cold
- •Aches: prominent muscle and body aches with flu; mild with a cold
- •Exhaustion: marked tiredness with flu; mild with a cold
- •Cold symptoms like a runny or blocked nose and sneezing are common in both, but more prominent with a cold
Treating a cold or flu at home
There is no cure for colds or flu, as antibiotics do not work against viruses, but most people recover at home with rest and simple measures. Helpful steps include resting, keeping warm, and drinking plenty of fluids to avoid dehydration. Over-the-counter remedies can ease symptoms: paracetamol or ibuprofen can reduce fever and aches, and a pharmacist can advise on suitable products for congestion or a sore throat.
Other soothing measures include warm drinks, honey and lemon for a sore throat or cough (not honey for babies under one), and steam inhalation for congestion. Most colds clear within about a week, while flu can take up to two weeks, with tiredness sometimes lingering longer. If you are not improving as expected, or symptoms worsen, it is worth seeking advice.
Preventing colds and flu
Good hygiene reduces the spread of both colds and flu. Washing your hands regularly, especially after coughing, sneezing or being in public places, is one of the most effective measures. Catching coughs and sneezes in a tissue and binning it, and avoiding touching your face, also help, as does staying away from others when you are unwell to avoid passing it on.
For flu specifically, an annual flu vaccine offers protection and is recommended for those at higher risk of complications, including older adults, pregnant women, young children and people with certain health conditions. The vaccine is updated each year to match circulating strains. General healthy habits — good sleep, a balanced diet and not smoking — also support the immune system in fighting off infections.
When colds and flu lead to complications
Most colds and bouts of flu resolve without problems, but sometimes they can lead to complications, particularly flu. A cold or flu can occasionally be followed by a secondary infection, such as a chest infection, sinus infection or ear infection, when bacteria take hold after the initial viral illness. Signs that this may be happening include symptoms that worsen after starting to improve, a returning fever, or new symptoms like ear pain or a productive cough with breathlessness.
Flu can more rarely lead to serious complications, especially in higher-risk groups. These include pneumonia and the worsening of existing long-term conditions such as asthma or heart disease. This is one of the key reasons flu is taken more seriously than a common cold, and why prevention through vaccination matters for those at higher risk.
Knowing the warning signs helps you act when needed. Difficulty breathing, chest pain, coughing up blood, confusion, a fever that will not come down, or being unable to keep fluids down all warrant prompt medical attention. For most people, though, colds and flu remain self-limiting illnesses that pass with rest and time.
Higher-risk groups and when to be cautious
While colds and flu are usually mild, certain groups are at higher risk of becoming more seriously unwell, particularly from flu. These include older adults, pregnant women, young children, and people with long-term health conditions such as asthma, diabetes, heart disease, or a weakened immune system. For these groups, flu warrants more caution and a lower threshold for seeking medical advice.
If you or someone you care for is in a higher-risk group and develops flu symptoms, it is worth seeking advice early, as antiviral medicines are sometimes recommended and work best when started promptly. The annual flu vaccine is also specifically recommended for these groups to reduce the risk of severe illness.
For babies and young children, extra care is needed, as they can become unwell quickly. Seek urgent help for a child with breathing difficulty, a persistent high fever, who is very drowsy or floppy, or who seems seriously unwell. For most healthy adults and children, however, a cold or flu is an unpleasant but temporary illness that resolves with home care.