These recommendations are consistent with those made by the Institute for Clinical Systems Improvement [ICSI, 2004] and are mainly based on consensus statements and narrative reviews.

• Diagnosis of the common cold is based on a cluster of signs and symptoms that is extensively described in the medical literature.
• Factors which may complicate the natural history of the cold should be recognized, to allow monitoring for complications (e.g. secondary bacterial infections).
• Recognizing serious illnesses before they become life threatening is a primary concern for the health care professional. People presenting with such illnesses at triage should be assessed immediately.

These recommendations are consistent with those made by the Institute for Clinical Systems Improvement [ICSI, 2004] and are mainly based on consensus statements and reports, narrative reviews, and medical opinion. The treatments recommended in this section are generally not suitable for investigation by randomized controlled trials (RCTs), owing to practical and economic reasons.

• Increased fluid intake. Despite being almost universally recommended, very little evidence supports increased fluid intake in the common cold. A Cochrane review (search date: July 2005) investigated this intervention but found no controlled trials suitable for inclusion [Guppy et al, 2005]. The author commented that limited evidence from observational studies suggested that too much fluid could be dangerous, especially in young children. Nevertheless, it is important to keep the body hydrated at all times, and as fluid loss is likely to be greater when fever and nasal discharge are present, it is prudent to drink more fluid than normal.
• Diet. There is no proof that specific diets are beneficial in people with the common cold. Furthermore, the available evidence from RCTs does not support the use of high doses of vitamins or minerals.
• Rest. At present, there is no evidence on whether rest is beneficial for the common cold. The best advice available is that people should remain as active as they can without feeling significant discomfort.
• Symptomatic remedies. In general, evidence to support the use of symptomatic remedies is lacking, but this does not necessarily mean they are ineffective, and anecdotal reports support their use. In general, it is thought to be better to use safe traditional remedies than to use ineffective over-the-counter medicines:
• Steam inhalation is reputed to reduce nasal decongestion by loosening mucous and inhibiting virus replication. The efficacy of steam inhalation was the subject of a Cochrane review (search date: December 2005) which identified six trials of the intervention [Singh, 2006]. Most of the trials reported positive outcomes, with an overall symptom relief risk reduction of 0.56 (95% CI 0.40 to 0.79). However, the authors warned of the dangers of steam inhalation, in particular scalding in young children.
• Vapour rubs have been shown to be beneficial in children with bronchitis [Berger et al, 1978], but evidence for their efficacy in the common cold is lacking. However, some children like the sensation of the rub and may experience a degree of symptom relief.
• Gargling with salt water has not been shown to be effective by any study, but there are anecdotal reports that it may soothe a sore throat, and it is unlikely to be harmful.
• Menthol lozenges have little effect on nasal congestion using objective measurements, but they may create the sensation of improved airflow and therefore create a subjective improvement [Eccles et al, 1990].
• Saline nasal drops are thought to facilitate mucous drainage from the nose, but there are no controlled trials to verify this [MHRA, 2009].

The recommendation that paracetamol or ibuprofen should be used to treat symptoms of the common cold is based on historical use and extrapolated evidence from randomized controlled trials, and it is consistent with most guideline groups [ICSI, 2004; MeReC, 2006].

• Aspirin and other nonsteroidal anti-inflammatory drugs are not recommended, as they are more likely to cause serious adverse effects. In particular, aspirin should be avoided in groups including:
• Children younger than 16 years of age, because of the risk of Reye's syndrome.
• Older people who are more prone to its adverse effects, or who are taking concomitant nonsteroidal anti-inflammatory drugs or aspirin for cardiovascular purposes.

The use of symptomatic treatments other than simple analgesia is not recommended by most guideline groups or expert reviewers [ICSI, 2004; MeReC, 2006]. In general, the benefits of other treatments are outweighed by their potential to harm or by other considerations. For detailed information on the available evidence from randomized controlled trials (RCTs) for these treatments, see Supporting evidence.

• Antibiotics would not be expected to be effective for the treatment of the common cold, which is caused by viral rather than bacterial infection:
• This ineffectiveness was confirmed by a systematic review [Arroll and Kenealy, 2005].
• In addition to being ineffective, antibiotics may cause adverse effects. One review found that for every 16 people treated, one would have an adverse effect (NNH = 16) [Arroll, 2006].
• Antihistamines used alone have been shown to be ineffective by a systematic review [De Sutter et al, 2003]. Sedating antihistamines may reduce some symptoms when combined with a decongestant (probably because they have anticholinergic effects), but the risk of adverse effects (e.g. drowsiness) outweighs any benefit of this approach. Non-sedating antihistamines are completely ineffective.
• Vitamin C and zinc are the most commonly recommended vitamins and minerals. However, the available evidence for vitamin C suggests that it has an effect only when taken at large doses as prophylactic treatment, and the benefit is likely to be small [Douglas et al, 2004]. The evidence for the use of zinc is even less convincing [Marshall, 2006].
• Complementary and alternative therapies are increasingly popular treatments for colds, but there is little evidence to support their use in the treatment or prevention of the common cold.
• Echinacea has shown some benefit in RCTs, but the optimum formulation is unknown and quality control remains a problem [Linde et al, 2006].
• Chinese herbal medicines have not been shown to be effective by high-quality controlled trials [Wu et al, 2007].
• Over-the-counter cough and cold products containing certain ingredients should no longer be used in children under 6 years, because the balance of benefits and risks has not been shown to be favourable [MHRA, 2009].
• A Medicines and Healthcare products Regulatory Agency (MHRA) review examined the safety and efficacy of children's cough and cold medicines, and found there is no good evidence that they work. There have been some reports of harm, for example, rarely they can cause side effects such as allergic reactions, effects on sleep, and hallucinations [MHRA, 2009].
• For children over 6 years of age, it is felt that these risks are reduced, as with increased age and size, these medicines are tolerated better [MHRA, 2009].
• In addition, there is no convincing evidence from RCTs that cough medicines make a clinically significant difference to cough or other cold symptoms, but they may have a useful placebo effect [Schroeder and Fahey, 2004].
• Decongestants are available as topical or oral preparations. Evidence from a systematic review indicates that decongestants relieve nasal congestion in the short term, but this effect does not extend past a few days, and the benefit is relatively small [Taverner and Latte, 2007].

The practical advice given in this section is consistent with that of the Institute for Clinical Systems Improvement, which is mainly based on expert consensus and extrapolation from the known mechanisms of transmission of viruses implicated in the cold (for details, see Transmission) [ICSI, 2004].

• Explaining that the incidence of the common cold is very high and infection at some stage is unavoidable may help to allay the person's fears.
• A major route of transmission of viruses involved in the common cold is direct bodily contact. Hand washing is thought to reduce transmission of the common cold [Turner and Hendley, 2005], but definitive evidence of clinical benefit from controlled trials is still lacking. Recently, trials have investigated the role of specialised hand washes in preventing the cold.
• A randomized controlled trial (RCT) found that a hand wash containing organic acids reduced transmission of rhinovirus but had no effect on the proportion of people who developed the common cold caused by rhinovirus [Turner et al, 2004].
• A RCT investigating an alcohol-based hand wash found that it reduced transmission of gastrointestinal viral infections but not respiratory infections [Sandora et al, 2005].
• A prospective cohort study found that the use of alcohol washes was associated with a lower transmission rate of respiratory illnesses [Lee et al, 2005].
• The incidence of the common cold in children has been shown to be related to their exposure to day-care facilities and the use of bottle-feeding [ICSI, 2004]. These are also thought to be risk factors in some complications of the common cold, such as acute otitis media. However, no recommendations can be made with regard to these risks, as usually they cannot practically be avoided.
• There is no evidence that vitamin or mineral supplements are effective in preventing the common cold.
• There is no evidence that travel by aeroplane increases the risk of developing the common cold [Mangili and Gendreau, 2005].

There are no UK guidelines on when it is appropriate to follow-up people with the common cold. Consequently, these recommendations are consistent with North American guidelines from the Institute for Clinical Systems Improvement [ICSI, 2004].

• The natural history of the common cold is for symptoms to peak after 3 days and start improving after 5 days (see the section on Prognosis for further details). Symptoms lasting longer than a week (with the exception of mild cough) are unusual and suggest the presence of a different illness, or that a complication may be present.
• The development of 'red flag' signs or symptoms is a cause for concern and should be investigated without delay.