The alleged health benefits of cough syrups have been questioned by consumer campaigners Which? and a panel of medical experts in Britain.
For instance, one manufacturer claimed that their preparation "works deep down to loosen phlegm, clear bronchial congestion, and make your cough more productive."
The product's key active ingredient is guaifenesin, but the experts said the studies which are used to support the claims of its effectiveness are low quality. Nor has the company provided any evidence of effectiveness, say experts.
The active ingredients of another mixture are sugar alcohol (glycerol) and liquid sugar (sucrose). It also includes other sugars such as black treacle. The experts said the mixture is roughly half sugar and its effectiveness is "unproven".
The experts also found out that one week of the adult maximum dose of the Benylin Tickly Coughs mixture is equivalent to eating the sugar contained in five Mars bars.
The team was similarly sceptical about the claims made for Covonia Herbal Mucus Cough Syrup. Which? said companies must be honest about what these products - which are often expensive - can do, particularly when it comes to important issues like health.
A spokesman said: "We spend billions on over-the-counter pharmacy products each year but we've found evidence of popular products making claims that our experts judged just aren't backed by sufficient evidence. Companies should be upfront with the evidence behind the claims they make so that consumers can make an informed decision."
A number of studies have identified glucosamine, omega 3 and chondroitin as having beneficial effects in terms of protecting ageing joints. And various medicines have latched on to these claims in order to increase sales.
But the European Food Safety Authority (EFSA) recently ruled the evidence was not strong enough to substantiate the claims.
Seven Seas Jointcare Be Active tablets contain the three ingredients and use the marketing claim: "Keep really active with this everyday plan to look after your joints."