Colds are viral infections of the nose and throat. Colds can go on to involve the sinuses, ears, larynx (vocal cords), trachea and bronchi directly or through secondary effects. The presence of the virus causes inflammation of membrane linings, so that there is swelling with obstruction (stuffiness) and increased mucous secretions. Colds are the most common type of respiratory infection; they are usually mild illnesses that naturally come to an end, only occasionally leading to further problems.
There are many viruses that can cause colds, sometimes seasonally and sometimes in epidemics. Up to 50% of colds are caused by one of the more than 100 rhinoviruses (rhino = nose). Other viruses that cause colds are the coronaviruses, adenoviruses, respiratory syncytial virus and parainfluenza viruses. Some of these viruses are capable of causing more severe disease in very young infants (such as pneumonia), but only cause colds in older children and adults.
A person with a cold is usually contagious from 24 hours before the beginning of symptoms and as long as the symptoms last, which is usually about a week. Rhinoviruses are most often spread by direct contact with infected secretions, e.g. touching objects such as handkerchiefs, door-knobs or eating utensils that a person with a cold has touched before, and then touching one's nose or mouth. Rhinoviruses are less often spread by airborne particles, such as when an infected person sneezes.
Your immune system responds by attacking the virus with white blood cells. If your immune system cannot recognise the virus from a previous infection, the response is "non-specific", meaning your body produces as many white blood cells as possible and circulates them to the infected sites. White cells produce chemicals to kill virus-infected cells, and this is what causes the nasal inflammation and swelling, increased mucous secretions and the general feeling of achiness. Once infected with a specific cold virus, the body develops immunity to it in the form of "memory white cells" and antibodies, which will control the virus quickly in the event that it is encountered again. Immunity will prevent another cold being caused by the same rhinovirus for some months at least, but does not protect against others.
One to three days after exposure, the illness begins with sore throat, discomfort in the nose and sneezing, soon followed by a running nose and unwellness.
Colds are typically not associated with high fever, which should not reach more than 38.5°C. Headache, tiredness and muscle aches can occur. The watery secretions thicken during the first day and become yellow or green in colour, due to the presence of white cells. This is the time when bacterial infection might worsen the illness. Since the lining of the upper airways is now inflamed, it is easier for normal bacteria inhabiting the surfaces to invade. In addition, blockage of the narrow air passageways from the nose to the sinuses allows accumulation of mucous secretions in the sinuses in which bacteria can multiply. Similarly, the eustachian tube from the throat to the middle ear can close up, leading to middle ear infection (otitis media). In children the virus itself can cause middle ear and sinus infections.
A post-nasal drip, where infected secretions run down the back of the throat, (often causing an uncomfortable burning sensation) is not an uncommon sequel of a cold. Laryngitis and inflammation of the trachea can be consequences of the variable extension of the viral and/or bacterial infection into the upper airways. Inflammation and swelling of the vocal cords so that they no longer move properly is what causes the loss of voice in laryngitis. Further progression down the airways leads to bronchitis. Coughing is due to the irritation of the linings of these airways. Coughing is often worse in bed at night or on rising in the morning due to movement of secretions in response to a change in position. If other symptoms are improving, and the cough does not persist and is not productive, it is not a cause for concern.
Colds can also worsen other underlying illnesses. Chronic bronchitis due to for example smoking can flare up with increased coughing and sputum production, and the spasm of the airways in asthmatics can be significantly worsened, bringing on an sudden asthmatic episode.
When no complications occur, a cold should be over in four to 10 days.
Colds can occur during any season and can affect anyone. Children get colds far more often than adults do. This may be due to the fact that they touch their faces and noses after touching other objects a great deal, and also because they haven't been exposed to as many viruses and have not had time to build up the kind of immunity that adults have.
When to see a doctor
Call a doctor if:
- An infant less than 6 months old develops a fever higher than 38.5°C.
- There are signs of noisy and obvious efforts with inhaling, and a barking cough following a cold in a small child. This is called croup and can lead to obstruction of the upper airway.
- There are severe coughing fits in a small child.
- You have a persistent (more than 10 days) productive cough with green, yellow, brown or rust-coloured sputum coughed up from the lungs, rather than the back of the throat. Post-nasal drip (mucus running down the back of the throat from the nasal passages) can often cause a cough during a cold, and you may spit up some mucus. However, this is different to a productive cough where the sputum is definitely coming from the lungs rather than the nasal passages, especially if this is associated with fever.
- You experience difficulty breathing or produce whistling/wheezing noises when you breathe.
- Sinus pain persists after two to four days of home treatment, especially if nasal discharge is coloured rather than clear, and you also have fever and headaches.
- A persistent nasal discharge in the absence of cold symptoms, especially if the discharge is bloodstained.
- You have earache lasting longer than 24 hours, or severe ear pain lasting for an hour.
- You have any throat pain that lasts longer than three to four days, which seems different to a normal cold.
The diagnosis of colds is most commonly made based on symptoms and signs. Fever and more severe symptoms suggest influenza.
Most colds will be over in 7 to 10 days, and can usually be treated at home. If there is a mild fever and a feeling of lethargy in the early stages of a cold, bed rest is advisable.
The following are some practical methods that may help to alleviate cold symptoms:
- Inhale steam, with or without aromatic oils such as eucalyptus or camphor, but be careful to avoid burns.
- Use over-the-counter cold preparations available at pharmacies. Most of these contain aspirin or paracetamol with or without codeine, and a decongestant (vasoconstrictor) such as pseudoephedrine to reduce nasal stuffiness. Pseudoephedrine should not be taken if you have heart disease, high blood pressure, prostrate problems, diabetes or thyroid problems. Do not give aspirin-containing medications to children with viral infections.
- Antihistamine preparations are of little value in colds unless one has an allergic tendency. Drowsiness may be a problematic side effect.
- Some cough preparations ease a dry, hacking cough, but a wet cough should not be suppressed, as it is important to cough up infected lung secretions.
- Mucolytics (mucus-thinning agents) such as carbocisteine may help to thin nasal mucus and allow it to drain, which may help prevent secondary bacterial infections such as sinusitis.
- Antibiotics will not improve cold symptoms and will not prevent a bacterial infection from developing after a cold. However, antibiotics may be prescribed for bacterial complications such as sinusitis or ear infections.
- It has been suggested that use of vitamin C can alleviate symptoms, especially if taken early on in the course of the illness. However, no scientific evidence exists to prove or disprove this advice. Doses of 1 to 2 g a day may shorten the duration and severity of colds, but this varies. Do not use such high doses of Vitamin C for long periods.
- If you're prone to herpes infections (cold sores) on your lips, start applying aciclovir cream to the areas where you usually get the sores: this might prevent cold sores from appearing, and if they do appear, they will be less severe.
There is no sure way to prevent colds, especially in children. As children grow into adults, they naturally get fewer colds.
The following may help protect you against catching colds:
- Wash your hands often, especially when you are around people with colds.
- Stop smoking. Smoking irritates the mucous membranes of the nose, sinuses, and lungs, which may make them more susceptible to infections.
- Keep your stress levels under control. If you are exposed to cold viruses, a high level of stress may increase your chances of catching a cold.
- When you have a cold, avoid sneezing without covering your mouth. Also avoid spreading nasal secretions on your hands.
- Use disposable tissues rather than a handkerchief.
Colds can't be prevented with:
- Antibiotics, which also will not prevent complications.
- Large doses of vitamin C, zinc or other vitamins and minerals
- The flu vaccine, which only protects against the influenza virus
Look after yourself!