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The NHS says there's "no good-quality evidence" that homeopathy is effective as a treatment for any health condition, yet it funds it. Why and to what extent?

Homeopathy is an extremely controversial issue - so it's no surprise it came top of our poll of readers when we asked what they would like us to investigate.

The Department of Health doesn't hold any figures for England - nor do the other devolved nations - so instead I've had to go to a variety of different sources to get a picture of what is happening.

There are now only two NHS centres offering homeopathic treatments - in London and Glasgow. Another two former ones - in Bristol and Liverpool - have moved into the private sector, but still see NHS patients (although it was announced this week the last health body funding the Liverpool one was going to stop sending patients).

However, the way money flows around the health service makes it hard to work out exactly how much is spent across these sites.

For example, patients receiving fertility treatment or being given support for pain or anxiety may get referred to these centres, but are not necessarily recorded as receiving homeopathic care.

Nonetheless, the Good Thinking Society, which has been campaigning for the NHS to stop funding homeopathy, estimates spending is in the region of £5m a year.

Why Nick wrote this article:

We asked readers to send BBC health correspondent Nick Triggle questions on the NHS.

Nick chose four questions and we asked you to pick your favourite, which came from Andrew Toppleman, a 30-year-old finance worker. His question was by far the most popular of the four that Nick selected.

In total, 3,577 people chose a question and Andrew's came first after being selected by 1,184 people.

Andrew asked: "Why are effective drugs denied to people on the basis of cost while millions are wasted on homeopathy?"

He told us why homeopathy in the NHS mattered to him.

"Why do we talk about raising more money for the NHS when the money we do spend isn't being spent effectively? It doesn't matter if its £100 or £10m pounds spent on homeopathy - if it does not work then it is a waste."

The NHS also funds homeopathic remedies through prescriptions, but that doesn't amount to much in monetary terms. Last year there were nearly 9,000 issued at a cost of £94,000 in England - and that doesn't take into account any money raised through prescription charges.

So let's call it about £5m of NHS funding for homeopathy each year. I put that figure to the British Homeopathic Association and they agreed it was likely to be in that ballpark.

Now that sounds a lot of money, but to put it into context the total amount spent on the health service across England, Scotland, Wales and Northern Ireland is more than £130bn. It means less than 0.004% of the budget goes on homeopathy.

It is a tiny fraction - a "drop in the ocean" says the association - albeit enough to pay for an extra 200 nurses or 50 consultants.

How homeopathic pills are made

Homeopathy is based on the concept that diluting a version of a substance that causes illness has healing properties

For example, pollen or grass could be used to create a homeopathic hayfever remedy

One part of the substance is mixed with 99 parts of water or alcohol and this is repeated six times in a "6c" formulation or 30 times in a "30c" formulation

The end result is combined with a lactose (sugar) tablet

Homeopaths say the more diluted it is, the greater the effect. Scientific consensus says patients are getting nothing but sugar

Common homeopathic treatments are for asthma, ear infections, hayfever, depression, stress, anxiety, allergy and arthritis

Source: British Homeopathic Association

So why does the NHS fund it, given it doesn't even seem to believe it works? To understand that we need to go back to the start of the NHS.

Homeopathy has been used since the 1800s and by the time the health service was created in 1948 there were five homeopathic hospitals - the four mentioned above plus another in Tunbridge Wells in Kent which closed in 2009.

Unlike now, there was not such a vociferous campaign against its use and so homeopathic treatments were brought under the NHS umbrella, where they have remained ever since.

That contrasts sharply with the approach taken to treatments now. In 1999 a drugs advisory body called the National Institute of Health and Care Excellence was set up to carefully assess the cost-effectiveness of new drugs and technologies in England, Wales and Northern Ireland (Scotland has a slightly different system).

It has looked at over 600 treatments since, taking into account cost, how effective they are and whether there are other similar treatments available. The treatments NICE rejects get the headlines so it may come as a surprise to many that they have actually agreed to recommend over 80% for NHS use.

So with ever-greater emphasis on evidence-based medicine - plus the increasing strain on resources - a growing clamour for an end to homeopathy funding has developed.

In 2010 the House of Commons' Science and Technology Committee called for NHS funding to stop as there was no evidence beyond a placebo effect (when a patient feels better because of their belief that the treatment works). Others, including the British Medical Association, have followed suit.

The problem is that short of the government stepping in, which it hasn't done, there is no clear mechanism for this to happen.

Instead, it has been left for others to chip away at homeopathy's continued use - and this has happened.

Twenty years ago there was close to £1m a year spent on homeopathic prescriptions, but the figure now is 10 times less, while NHS homeopathic centres have found themselves disappearing.

Homeopathy, it could be said, is a historical anomaly, but one there seems to be a determination to rectify.