Review question
We reviewed evidence for the effectiveness of antihistamines on signs and symptoms of the common cold. We identified 18 trials with 4342 participants.
Background
On average, young children have six to eight colds per year and adults have two to four. Common cold symptoms include sore throat, nasal stuffiness and discharge, sneezing and cough. It is caused by viruses and usually resolves by itself within one to two weeks. However, the common cold has a large impact on time off work or school.
As there is no cure for the common cold, only symptomatic treatment is available. Antihistamines are effective for allergic symptoms such as hay fever. Nasal symptoms of hay fever are similar to common cold symptoms and so trials have been conducted to see whether antihistamines improve common cold symptoms.
Study characteristics
The evidence is current to August 2015.
The participants were adults or children with a common cold. We excluded studies with participants suffering from hay fever, asthma or eczema. The effect of different antihistamines was compared to placebo. A beneficial effect meant a decrease in the severity or duration of the general feeling of illness and/or of specific symptoms such as stuffy nose, runny nose or sneezing. We also investigated whether side effects were more common with antihistamines than placebo.
As the common cold usually resolves in seven to 10 days, most studies were of short duration. Where possible we studied the immediate effect and the effect after six to 10 days. Most studies were of good quality although in some studies information to allow us to assess quality was lacking. We considered five out of 16 adults studies and one out of two paediatric studies to be of excellent quality.
All trials outlined the financial support received from pharmaceutical companies in the form of grants, supplying the respective intervention drug or having an author currently employed by a pharmaceutical company.
Key results
In adults, there is a short-term beneficial effect on severity of overall symptoms on the first or second day of treatment (45% felt better versus 38% with placebo), but there was no difference between antihistamines and placebo in the mid to long term. The effect of sedating antihistamines on rhinorrhoea and sneezing is too small to be relevant to the patient and involves a risk of side effects such as sedation (9% versus 5.2% with placebo). Trials in children were smaller and of lower quality and lacked evidence of effectiveness.
Antihistamines have a limited short-term (days one and two of treatment) beneficial effect on severity of overall symptoms but not in the mid to long term. There is no clinically significant effect on nasal obstruction, rhinorrhoea or sneezing. Although side effects are more common with sedating antihistamines, the difference is not statistically significant. There is no evidence of effectiveness of antihistamines in children.
The common cold is an upper respiratory tract infection, most commonly caused by a rhinovirus. It affects people of all age groups and although in most cases it is self limiting, the common cold still causes significant morbidity. Antihistamines are commonly offered over the counter to relieve symptoms for patients affected by the common cold, however there is not much evidence of their efficacy.
To assess the effects of antihistamines on the common cold.
We searched CENTRAL (2015, Issue 6), MEDLINE (1948 to July week 4, 2015), EMBASE (2010 to August 2015), CINAHL (1981 to August 2015), LILACS (1982 to August 2015) and Biosis Previews (1985 to August 2015).
We selected randomised controlled trials (RCTs) using antihistamines as monotherapy for the common cold. We excluded any studies with combination therapy or using antihistamines in patients with an allergic component in their illness.
Two authors independently assessed trial quality and extracted data. We collected adverse effects information from the included trials.
We included 18 RCTs, which were reported in 17 publications (one publication reports on two trials) with 4342 participants (of which 212 were children) suffering from the common cold, both naturally occurring and experimentally induced. The interventions consisted of an antihistamine as monotherapy compared with placebo. In adults there was a short-term beneficial effect of antihistamines on severity of overall symptoms: on day one or two of treatment 45% had a beneficial effect with antihistamines versus 38% with placebo (odds ratio (OR) 0.74, 95% confidence interval (CI) 0.60 to 0.92). However, there was no difference between antihistamines and placebo in the mid term (three to four days) to long term (six to 10 days). When evaluating individual symptoms such as nasal congestion, rhinorrhoea and sneezing, there was some beneficial effect of the sedating antihistamines compared to placebo (e.g. rhinorrhoea on day three: mean difference (MD) -0.23, 95% CI -0.39 to -0.06 on a four- or five-point severity scale; sneezing on day three: MD -0.35, 95% CI -0.49 to -0.20 on a four-point severity scale), but this effect is clinically non-significant. Adverse events such as sedation were more commonly reported with sedating antihistamines although the differences were not statistically significant. Only two trials included children and the results were conflicting. The majority of the trials had a low risk of bias although some lacked sufficient trial quality information.