SIMON PERRY belongs to a group called Skeptics in the Pub, which seeks to rigorously and openly apply the methods of science and reason to commonly held beliefs and claims. In his occasional column for the Mercury, he reveals the results of his investigations.

Trust Boots is the tagline that has been offered by the high street pharmacist since 2005.

According to Boots' 2006 Corporate Responsibility Strategy, "Everything we do that builds trust is good for our business; anything which could compromise it, a risk we can't afford to take."

So has Boots shown itself to be worthy of our trust?

On the shelves of the pharmacy in Gallowtree Gate in Leicester you will find a small section devoted to homeopathy.

Many people I meet are confused about exactly what homeopathy is – some thinking it is simply a type of herbal or natural medicine.

Allow me to explain.

The first principle of homeopathy is what they call the "law of similars".

Homeopaths look for a chemical that produces a similar symptom to the disease they aim to treat.

For instance, caffeine causes you to stay awake, so homeopaths may decide to use this in a remedy to treat insomnia.

Another example is hay fever. Hay fever causes runny eyes and so do onions – so some homeopaths will treat hay fever with a preparation of onions.

I realise that all this may sound a little bit unconventional, but please bear with me.

Turning a chemical such as onion juice into a homeopathic preparation involves a process of "dilution" and "succussion".

To create the centesimal or "C" remedies they sell at Boots, the homeopath takes one drop of the chemical and mixes it with 99 drops of water (dilution).

In centuries past, this was then banged against a leather covered board or book, often a bible, although in modern times the shaking is often done by machine.

This shaking is called "succussion". This is now a 1C homeopathic preparation. It contains 99% water and 1% "active ingredient".

To turn this into a 2C remedy, the process is repeated. One drop of the solution is taken from the 1C remedy is mixed with 99 drops of water and then shaken.

The 2C remedy now contains 99.99% water and 0.01% "active ingredient".

Repeat the process again to create a 3C remedy at 0.0001%, and so on.

Homeopaths believe that the higher the level of dilution, the more powerful the remedy.

Many homeopaths will use the solution directly, but Boots and many others prefer to sell homeopathy as pills – or pillules as they call them.

One pillule is meant to contain the equivalent of one drop of homeopathic solution. We can calculate approximately how many molecules of "active ingredient" get into the one drop that makes it into the pillule. A drop of water contains about 1,700,000,000,000,000,000,000 molecules. Scientists write this as 1.7x1021. That's a 17 with 20 zeros after it.

Boots sell remedies at 6C and 30C. A 6C remedy will contain about 0.0000000001% "active" ingredient – which works out at about 1.7 billion molecules of active ingredient.

But what about when we dilute this further? By the time you get to 10C, there are only 17 molecules of active ingredient left. And at 11C, you only have about a one chance in six of finding a single molecule.

The branch of Boots, in Gallowtree Gate, display a guide, provided by the manufacturer, that states a Bryonia 30C remedy "Relieves the symptoms of a dry painful cough, pressure and dehydration headaches" and that a Kali Bich 30C remedy "Soothes the symptoms of sinusitis".

I have already explained that at 11C, you only have about a one-in-six chance of finding a single molecule of active ingredient.

At 12C, there is only about one chance in 600 that you will find a molecule and at 13C just one chance in 60,000.

By the time you get to 30C, you have more chance of winning the National Lottery jackpot five weeks in a row than you do of finding a single molecule of active ingredient.

Or think of it this way – how much water would you need to contain one molecule of active ingredient at 30C dilution?

According to my calculations, the body of water would weigh five billion times more than the planet you are standing on.

If you want that in pillule form, you'd need to buy 6x1038 pillules (a six with 38 zeros after it).

At Boots' retail prices, that would cost you 35 trillion trillion trillion pounds. That's a rather expensive molecule.

To my way of thinking, homeopathy is entirely implausible, but science is incredibly open-minded to seemingly implausible ideas.

Ideas such as Einstein's theory of general relativity and quantum theory are utterly bizarre, but once they were demonstrated to be true with fair tests then scientists accepted them.

Testing for a pill is essentially simple. Take a large number of people with a particular disease and randomly divide them into two groups.

Give one group the pills you want to test and the other group some placebo pills that don't contain anything.

Neither the patient, nor the researchers working with them can know which patients were given which pill.

After an agreed period of time count how many people in each group got better. So what do the trials show? Actually, that's a little complicated.

Some of the poor quality trials where the patients were told which drug they were getting, or had very small sample sizes showed an effect.

But those effects could easily be down to the placebo effect, or random variation due to the small sample sizes.

But when the experiments are done properly with larger numbers of patients, the vast majority do not show homeopathy to be any better than a placebo.

A quick search of scientific journal, the Cochrane Library, articles leads us to reviews of homeopathy treatment of dementia, asthma and attention deficit/hyperactivity disorder.

They all end in similar conclusions: "No evidence that homeopathy is effective in treating dementia", "until stronger evidence exists for the use of homeopathy in the treatment of asthma, we are unable to make recommendations about homeopathic treatment" and "overall the results of this review found no evidence of effectiveness for homeopathy for the global symptoms, core symptoms or related outcomes of attention deficit/hyperactivity disorder."

But what do they tell you in Boots?

When I popped into their Oadby branch and asked about homeopathic treatment, the pharmacist tried to politely steer me away from the homeopathic remedies citing the lack of evidence. Fair enough.

But a pharmacist at the Gallowtree Gate branch was not so off-putting.

Despite a couple of points in the conversation where I felt she certainly gave the impression that she did not believe in homeopathy, she was still happy to say things I would never expect to come out of the mouth of professional pharmacist, by explaining that homeopaths "don't just treat the condition, they look at the whole person".

Boots' professional standards director Paul Bennett was asked about homeopathy at a parliamentary science and technology sub-committee on the October 25: "Do they work beyond the placebo effect?"

He replied: "I have no evidence before me that they are efficacious and we look very much for the evidence to support that."

I think it's unlikely Boots don't know where to look for medical evidence.

So what we're being told by Boots' professional standards director is that they've looked around, found evidence – but he hasn't found anything that shows homeopathy to work.

He was asked to clarify with the line, "You sell them, but you don't believe they are efficacious?"

He replied: "It's about consumer choice for us."

There is no doubt that Boots is a reputable firm, establishing itself as the country's leading pharmacy chain.

I feel, therefore, it has a responsibility to make it clear that these homeopathic products do not work – or better still, not to sell them at all.

That way we would feel more confident when they ask us to "trust Boots".

Skeptics in the Pub is a monthly lecture series held in cities, including Leicester.

Speakers are usually scientists or a prominent sceptic and the talks range from subjects such as alternative medicine to religious beliefs.

http://leicester.skepticsinthepub.org