Different causes
A cold is a viral infection of the nose and throat, most often caused by rhinoviruses. It spreads from person to person through droplets and contaminated hands, and adults typically catch two to four a year, children more.
An allergy (allergic rhinitis) is not an infection. The immune system mistakes harmless particles such as pollen, house dust mite, animal dander or mould for a threat and releases histamine and other chemicals that inflame the nose and eyes. Allergies are not contagious and often run in families together with asthma and eczema.
Symptoms side by side
- Itchy eyes, nose or throat: common in allergies; rare in colds.
- Sneezing: both, but frequent bouts of sneezing are typical of allergies.
- Runny nose: clear and watery in allergies; clear at first, then often thicker, yellow or green in colds.
- Blocked nose: both.
- Sore throat: common at the start of a cold; in allergies, more of an itchy or scratchy throat from postnasal drip.
- Fever: possible with colds, especially in children; never caused by allergies.
- Aches and tiredness: common with colds; allergies cause tiredness mainly from poor sleep.
- Cough: both; see can allergies make you cough.
Timing and duration: the strongest clue
- Onset: colds develop over one to two days; allergies start within minutes to hours of exposure.
- Duration: colds usually improve within 7 to 10 days, although a cough can last up to three weeks; allergies last as long as you are exposed, often for weeks or months.
- Pattern: allergies recur at the same time each year (seasonal) or in the same places (at home, at work, around pets); colds come and go, more often in autumn and winter.
- Contacts: colds often spread through the family or office; allergies do not.
Allergies can also happen in the colder months; see winter allergies.
What about flu, COVID-19 and sinusitis?
- Flu: sudden high fever, marked aches, exhaustion and dry cough; usually more severe than a cold.
- COVID-19: can look like a cold or flu; loss of smell or taste, fever and cough are common. Testing is the only way to be sure.
- Sinusitis: facial pain or pressure, thick discharge and reduced smell for more than 10 days, or worsening after initial improvement; see sinus infection symptoms.
- Non-allergic rhinitis: a runny or blocked nose triggered by temperature changes, smells or alcohol, without itching; see non-allergic rhinitis.
Treating a cold
- Rest, fluids and warm drinks.
- Paracetamol or ibuprofen for fever, aches or sore throat, if suitable.
- Saline nasal sprays or rinses, and steam, for congestion.
- Decongestant sprays for no more than five to seven days.
- Honey and lemon for a sore throat or cough in adults and children over one year.
- Antibiotics do not help colds.
For throat symptoms, see sore throat remedies.
Treating an allergy
- Identify and reduce exposure to triggers, such as pollen, dust mites, pets or mould.
- Saline nasal rinses to wash allergens out.
- A steroid nasal spray every day during the allergy season or continuously for year-round allergies.
- Non-drowsy antihistamine tablets, nasal sprays or eye drops for itching and sneezing.
- Allergy testing to confirm triggers, and immunotherapy for persistent allergies.
Treating the nose often improves sleep, concentration and asthma control.
Can you have both at the same time?
Yes. People with allergies catch colds like anyone else, and an allergic nose can be more swollen and slower to recover during a cold. If your usual allergy symptoms suddenly change, with a sore throat, aches, fever or thick coloured mucus, a cold or infection is likely on top of the allergy. Continue your allergy treatment and add cold remedies as needed.
When to see a doctor
- Symptoms lasting more than 10 days without improvement, or getting worse after improving.
- High fever, severe headache or facial pain.
- Breathlessness, wheeze or chest pain.
- Swelling around the eyes or changes in vision.
- Symptoms on one side of the nose only, with bleeding.
- Allergy symptoms not controlled by treatment from the pharmacy.
- Swelling of the lips, tongue or throat after exposure to an allergen: call emergency services.
Key points to remember
- Itching, sneezing bouts and clear mucus without fever suggest allergy.
- Sore throat, aches, fever and improvement within 10 days suggest a cold.
- Timing and pattern are the most useful clues.
- Colds need rest and simple remedies; allergies need avoidance and nasal sprays.
Questions about allergies vs colds
These answers are general information and do not replace an examination or individual medical advice.
How can I tell if I have allergies or a cold?
Allergies cause itching, sneezing and clear mucus without fever and last weeks. Colds often start with a sore throat, may cause fever and aches, and clear within about 10 days.
Can allergies cause a fever?
No. A fever suggests an infection such as a cold, flu or COVID-19.
Can allergies turn into a cold?
No, but a swollen allergic nose can make you more prone to sinus problems, and you can catch a cold at the same time.
Does green mucus mean a cold rather than allergies?
Coloured mucus is more typical of a cold or sinus infection. Allergy mucus is usually clear and watery.
Do antihistamines help a cold?
They are designed for allergies. Some older drowsy antihistamines may dry a runny nose, but they do not shorten a cold.
How long do allergy symptoms last compared with a cold?
Allergies last as long as you are exposed, often weeks or a whole season. Colds improve within 7 to 10 days.
Sources
This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.