OVERVIEW

What is a cold?

A cold is an acute upper respiratory tract (nose, throat, and larynx) infection caused by viruses, often occurring during seasonal changes, winter, and spring.

Currently, it mainly refers to a syndrome characterized by symptoms such as sneezing, nasal congestion, runny nose, general discomfort, cough, sore throat, headache, and low-grade fever.

Colds are self-limiting illnesses and usually resolve on their own within 5–7 days, with a good prognosis^[1,2].

Are colds common?

Very common. On average, young children experience 4–8 colds per year, while adults experience 2–4 colds annually^[1].

What’s the difference between a cold, flu, and upper respiratory infection?

Flu: Influenza is a "severe" upper respiratory inflammation caused by the "influenza virus." Small-scale outbreaks are common, and viral mutations may lead to large-scale epidemics^[1].

Upper respiratory infection: This is a broader term referring to any inflammation of the upper respiratory tract caused by pathogens such as viruses, bacteria, or fungi, including colds^[1].

SYMPTOMS

What symptoms can a cold cause?

Common symptoms include nasal congestion, runny nose, throat itch, sore throat, cough, hoarseness, sneezing, watery eyes, headache, dizziness, fatigue, general discomfort, chills, and low-grade fever^[1].

Different viruses may cause different symptoms, but the type of virus cannot be determined based on symptoms alone.

For example, rhinoviruses are more likely to cause nasal symptoms such as congestion, runny nose, and sneezing; influenza and parainfluenza viruses are more likely to cause fatigue, body aches, headache, and fever; adenoviruses are more likely to cause sore throat and fever.

What are the early signs of a cold?

Early symptoms are mainly nasal catarrhal symptoms, such as sneezing, nasal congestion, and clear runny nose. In the initial stage, there may also be sore throat, dryness, itchiness, or a burning sensation in the throat^[2,3].

How long does a cold last?

It usually resolves within about a week^[2]. Some cases may clear up in as little as 3 days, while others may take up to 10 days, but generally no longer than 2 weeks. Studies show that smokers recover more slowly from colds.

Does thick or colored nasal discharge indicate a bacterial infection?

Not necessarily.

Cold sufferers may experience colored or purulent nasal discharge, but this does not confirm a bacterial infection, nor should it justify the misuse of antibiotics.

However, if a cold leads to viral or bacterial rhinosinusitis, purulent discharge may occur. Whether antibiotics are needed should be determined by a doctor after thorough examination and evaluation.

Can a cold cause diarrhea?

Yes, this is commonly referred to as "stomach flu" and is caused by viral damage to the intestinal lining. In addition to diarrhea, it may also cause vomiting.

What other illnesses can a cold lead to?

While colds usually resolve on their own, complications can occur. If symptoms persist for over a week without improvement or worsen, medical attention should be sought.

Common complications of colds include^[4]:

• Acute otitis media: Prolonged fever and ear pain.
• Acute rhinosinusitis: Purulent nasal discharge, nasal congestion, facial pain, and fever. It can be viral or bacterial.
• Lower respiratory tract infections: Such as bronchitis or pneumonia, marked by persistent fever, recurrent fever after initial improvement, worsening cough, increased or purulent phlegm, and possible chest pain or wheezing.
• Asthma flare-ups: Colds may trigger asthma attacks in some individuals.

CAUSES

Which viruses can cause the common cold?

The most common virus causing the common cold is rhinovirus, responsible for about half of all cold cases^[2].

Other viruses that can cause colds include coronaviruses, influenza viruses, parainfluenza viruses, respiratory syncytial viruses, adenoviruses, enteroviruses, and over 200 other types.

Does the body develop long-lasting immunity after being infected with a cold virus?

No.

Due to the wide variety of pathogens that cause colds, the immunity produced after infection is weak and short-lived, leading to repeated infections^[1].

Is the common cold contagious?

Yes, it is one of the most common infectious diseases^[1].

Most cold-causing viruses spread in the following two ways:

• Hand contact: When a person with a cold sneezes or coughs, they can spread the virus onto their skin or nearby objects, where the virus can survive for hours. Others may become infected by touching the sick person or contaminated objects and then touching their own mouth or nose.
• Droplets: When a person with a cold sneezes or coughs, they release virus-laden droplets into the air, which others may inhale, leading to infection.

Hand contact is the primary mode of transmission. However, not everyone exposed to the virus or droplets will develop a cold. The risk depends on the duration of exposure, closeness of contact, and the amount of virus encountered.

Does the common cold only occur in autumn and winter?

No, colds can occur year-round. Different viruses are active in different seasons:

• Rhinoviruses and parainfluenza viruses are more active in spring and autumn;
• Coronaviruses and respiratory syncytial viruses are typically active in winter and spring;
• Enteroviruses most commonly cause colds in summer;
• Adenoviruses can cause colds year-round and often lead to outbreaks in settings like military barracks, daycare centers, and hospitals.

Who is more susceptible to catching a cold?

Colds can affect anyone but are more common in the following groups^[3,4]:

• People under excessive psychological stress or pressure;
• Those who lack regular physical exercise;
• Individuals frequently in crowded environments;
• People with sedentary lifestyles;
• Those experiencing excessive fatigue;
• People with chronic sleep deprivation.

Who is more prone to severe colds?

• People with chronic conditions like diabetes, chronic bronchitis, heart disease, or kidney disease;
• Those with congenital immunodeficiency disorders;
• Individuals with malnutrition;
• Smokers.

What factors may contribute to catching a cold?

Seasonal changes, crowded environments, sedentary lifestyles, age, smoking, malnutrition, stress, excessive fatigue, insomnia, and weakened immunity are all risk factors for colds. Additionally, high psychological stress and tension (medically termed psychological stress) increase the risk of catching a cold, while regular physical exercise can reduce this risk^[3,4].

Can catching a cold be caused by exposure to cold weather?

Cold weather can trigger cold-like symptoms, classified under non-allergic rhinitis, but there is no direct link between cold exposure and viral colds. No scientific evidence suggests that cold climates increase the risk of viral infections.

However, since many viruses thrive in colder seasons and non-infectious non-allergic rhinitis is more common, colds are more frequently observed in autumn and winter.

DIAGNOSIS

Do I need any tests for a cold?

Generally not. Doctors can diagnose a cold through questioning and physical examination without requiring additional tests.

A physical exam includes measuring body temperature, observing the eyes, nose, and throat, and listening to the heart and lungs. Cold patients may have mild fever, conjunctival congestion, nasal mucosa swelling, or throat redness, but no heart murmurs (abnormal sounds during heart activity besides normal heartbeats)^[5] or lung rales.

If the doctor suspects conditions other than a cold after examination, they may recommend tests like blood tests, serology, or pathogen testing (e.g., nasal or throat swabs to identify the virus)^[1,3].

Can I self-diagnose a cold?

Yes.

Colds are common and usually mild, so you can self-diagnose without visiting a doctor. Symptoms typically include no fever or mild fever, thick nasal discharge after 2-3 days, sore throat, hoarseness, hearing loss due to eustachian tube inflammation, tearing, dulled taste, stuffy nose, and mild cough with little phlegm. Severe cases may involve fatigue, chills, body aches, and headaches^[2,4].

However, seek medical attention if symptoms persist or worsen, or if you’re unsure whether it’s a cold.

What diseases can be confused with a cold? When should I see a doctor?

Severe headache with nausea, vomiting, fever, personality changes, altered consciousness, or limb abnormalities may indicate encephalitis or meningitis.

Persistent fever with chest tightness, palpitations, or chest pain could signal viral myocarditis.

Extreme fatigue, nausea, vomiting, aversion to greasy food, dark urine, or jaundice may suggest hepatitis.

High fever, difficulty breathing, chest pain, or severe cough could indicate pneumonia or lower respiratory infections.

Prolonged fever, afternoon low-grade fever, weight loss, night sweats, or poor appetite may point to tuberculosis.

Seek medical help immediately if these symptoms occur to avoid complications.

How to distinguish a cold from allergic rhinitis?

Both share similar symptoms like sneezing, runny nose, and congestion. Key differences:

• Allergic rhinitis is triggered by allergens like pollen, dust mites, or cold air^[1].
• Allergic rhinitis starts suddenly with repeated sneezing and runny nose, while cold symptoms develop gradually.
• Allergic rhinitis subsides quickly after avoiding allergens, whereas a cold lasts about a week.

How to tell a cold from the flu?

The flu, caused by influenza viruses, is more severe and contagious than a cold^[1]. Symptoms include high fever (≥39°C), headache, extreme fatigue, muscle aches, chest pain, and worsening cough. Nasal congestion and sore throat are less prominent.

Colds can occur year-round, while flu peaks in winter/spring^[1] and spreads rapidly in crowded places. Cold symptoms focus on nasal congestion, runny nose, and sore throat, with rare fever or body aches.

How to differentiate a cold from bacterial pharyngitis/tonsillitis?

Bacterial infections mainly cause throat pain, dryness, or cough, while colds primarily affect the nose^[1].

Doctors can distinguish them via throat examination and blood tests.

TREATMENT

How to Treat a Cold?

A cold is caused by various viruses, and there are currently no specific antiviral drugs for these viruses, so it can be said that a cold is "incurable."

However, cold symptoms are usually mild, so most people do not need treatment and can simply wait for the cold to resolve on its own while staying hydrated and resting. If symptoms do not improve or even worsen after 3–10 days, medical attention should be sought.

For some patients with severe or intolerable symptoms, symptomatic treatment can be administered. Common medications are listed below.

What Are the Common Medications for a Cold?

Symptomatic treatment aims to relieve discomfort caused by the illness^[3,4].

There are many medications for symptomatic treatment of colds, with the most effective including^[3,4]:

• Antipyretics and analgesics: Such as ibuprofen and acetaminophen, which can relieve fever, sore throat, and body aches.
• Decongestants + Antihistamines: Common decongestants include pseudoephedrine, while common antihistamines include chlorpheniramine maleate. The combination of these two types of drugs can effectively relieve nasal congestion, runny nose, and sneezing. Using either alone may not provide ideal relief.
• Antitussives: Dextromethorphan is recommended for its strong cough-suppressing effect without causing dependence. However, it is not advised for young children.

Traditional medicine's adverse effects are unclear, so self-use is not recommended, especially for infants and young children. Neither modern nor traditional medications are advised for them.

If medication is needed, consult a doctor at a reputable hospital.

What Are the Side Effects of Common Antihistamines for Colds?

• First-generation antihistamines (e.g., chlorpheniramine maleate) can cross the blood-brain barrier, often causing drowsiness, reduced attention, and impaired cognitive function^[6]. Many cold medicines containing antihistamines warn against driving, operating machinery, or performing high-risk tasks after use. However, some nighttime cold medicines utilize this side effect to aid sleep.
• Second-generation antihistamines (e.g., cetirizine) reduce drowsiness but may have cardiac toxicity and weight gain as side effects^[6].
• Newer second-generation antihistamines (e.g., desloratadine) act faster, lack cardiac toxicity, and are safer for patients with liver or kidney dysfunction. Side effects like dizziness, dry mouth, headache, or nausea disappear quickly after discontinuation^[6].

To avoid drowsiness, check medication ingredients and avoid those containing chlorpheniramine, such as acetaminophen, ibuprofen, pseudoephedrine-based formulations, or phenylephrine combinations.

Do Colds Require Antibiotics?

Colds are viral infections, and antibiotics are ineffective against viruses. Using antibiotics increases drug resistance and may harm vital organs like the liver and kidneys, so they should not be used for colds^[1].

Antibiotics should only be used under a doctor's guidance if a bacterial (or other pathogen) infection is confirmed.

Is IV Fluid Therapy Necessary for Colds?

Generally, no. IV therapy does not speed up recovery and may cause adverse effects, such as:

• Fluid overload, increasing heart strain (risky for those with heart/lung disease or hypertension).
• Higher exposure to pathogens in hospitals, raising cross-infection risks.

How Should Special Populations (Pregnant Women, Children) Choose Cold Medications?

Pregnant/nursing women and children should consult a doctor before using cold medications.

• Pregnant women: Avoid aspirin, diclofenac, diphenhydramine, ibuprofen, and dextromethorphan to prevent fetal harm or prolonged pregnancy. Guaifenesin is prohibited in the first trimester^[3,7].
• Nursing women: Avoid diphenhydramine and chlorpheniramine, which can pass into breast milk.
• Children under 6: Medication risks often outweigh benefits. Use only approved pediatric formulations (e.g., syrups/suspensions) at weight-adjusted doses. Avoid aspirin due to fatal Reye’s syndrome risk^[3].
• Liver/kidney impairment, bleeding disorders, or ulcer history: Use acetaminophen, aspirin, or ibuprofen cautiously^[3,7].
• Drivers/machine operators: Avoid sedating antihistamines (e.g., chlorpheniramine, diphenhydramine)^[3].
• Uncontrolled hypertension/heart disease or MAOI users: Avoid pseudoephedrine^[3,8].
• Hyperthyroidism, diabetes, prostate enlargement: Use pseudoephedrine cautiously^[3].
• Glaucoma: Avoid pseudoephedrine^[3,8].
• COPD/severe respiratory insufficiency: Avoid codeine/dextromethorphan, as they may hinder mucus clearance^[3].

Disclose medical conditions and current medications when purchasing cold drugs.

What to Do About Persistent Post-Cold Cough?

Some experience prolonged coughing (≥8 weeks) after a cold, termed post-infectious cough. This results from airway hypersensitivity due to mucosal damage, not ongoing infection. Central antitussives (e.g., codeine) or antihistamines (e.g., chlorpheniramine) may help^[9].

Why Do Some Colds Last Longer?

While colds typically resolve in a week, prolonged cases may occur due to:

• Complications: Pre-existing conditions (e.g., COPD, asthma) worsening or secondary infections requiring additional treatment.
• Reinfection: Weakened immunity during a cold increases susceptibility to other viruses.

Which Department Should You Visit for a Cold?

Depending on symptoms, see respiratory medicine, general internal medicine, or fever clinics.

DIET & LIFESTYLE

What should people with a cold pay attention to in daily life?

• Get plenty of rest;
• Drink more water;
• Eat light, easily digestible, and nutritious food;
• Keep indoor spaces well-ventilated;
• Maintain a comfortable room temperature, avoiding extremes of cold or heat.

What dietary precautions should be taken after catching a cold?

There are no special restrictions or clear taboos in food choices, as long as the diet provides sufficient energy, balanced nutrition, and excludes allergenic foods.

If symptoms like sore throat or cough occur, drinking more water can help alleviate discomfort, so adequate hydration is essential.

During a cold, appetite often decreases, so overly greasy foods should be avoided. Opt for sweet, sour, or refreshing foods to stimulate appetite. Some people may experience gastrointestinal symptoms like diarrhea after a cold. In such cases, easily digestible foods like millet porridge, radishes, or soy products are recommended to avoid burdening the digestive system.

Can you exercise while having a cold?

A small number of individuals with strong constitutions and mild symptoms may continue exercising while sick.

However, for the elderly, those with weak immune systems, or chronic illnesses, exercise may strain the heart and lungs, potentially leading to severe cardiopulmonary dysfunction. Therefore, it is advisable to pause workouts and prioritize rest.

Can breastfeeding mothers nurse while having a cold?

Breastfeeding can continue normally during a cold, but precautions like wearing a mask and frequent handwashing should be taken to avoid transmitting the virus to the baby.

If cold symptoms are severe and require medication, drugs that do not affect breastfeeding can be chosen under a doctor's guidance.

PREVENTION

How to Prevent Colds?

Research shows that practicing good hand hygiene can prevent the spread of respiratory viruses, especially transmission from young children to others. Currently, the effective "Seven-Step Handwashing Technique" is promoted, focusing on cleaning seven key areas of the hands. The steps are as follows^[10]:

1. Rub palms together to clean the palms and centers of the hands;
2. Rub the back of one hand with the palm of the other to clean the backs of the hands and fingers;
3. Interlace fingers and rub to clean the fingers and gaps between them;
4. Clasp fingers and rub the backs of the fingers and nails;
5. Hold and twist the thumb of one hand with the other to clean the thumb and the webbed area;
6. Rub fingertips against the palm of the opposite hand to clean the nails and fingertips;
7. Hold and twist the wrist of one hand with the other to clean the wrists.