IF you have ever wondered about the integrity of the natural beauty products produced by Liz Earle, consider the search to find a replacement ingredient for the brand's top-selling haircare range.

Previously made with yangu oil, the hair range, including the favourite Botanical Shine Nourishing Hair Oil, had to be rethought when the oil, sourced from a sustainable co-operative in Kenya, was in short supply after droughts in two consecutive years.

"The actual yield of yangu has been appalling and we weren't able to secure enough of it to really use in our products," explains James Wong, ethnobotanist at Liz Earle.

"Legally we could have just reduced the quantity of yangu oil to an absolute minimum without changing the packaging and carry on selling it. But we didn't do that. When we couldn't get it any more we decided to withdraw the products and go back to the drawing board. Meanwhile we're still working with that community on long-term plantations of yangu."

As it is such a best-selling range, the brand didn't want to lose any time in finding replacement ingredients. Within 12 months it had found a selection of substitutions, tested them - on employees of the company rather than animals - and put the new and improved product back on the market.

They settled on the the Kalahari melon, a wild relative of the watermelon that is found in Namibia where the local San people used its oil to protect their skin from the harsh environment.

"Apart from benefits for the hair, in terms of conditioning, shine and preventing breakage, what I thought was great about it is being a wild relative of the watermelon and also relatively endangered in the wild, is that we are encouraging local people to cultivate it and this is really important for conservation," says James, who trained at the Royal Botanic Gardens Kew and is now based at the brand's headquarters on the Isle of Wight, where it has a collaboration with Ventnor Botanic Garden.

"With climate change, things like watermelons which are on the cusp of growing in hot, dry environments are under threat and we need to protect wild relatives of them to be able to have that gene pool to draw on for future breeding."

Until Kalahari melon oil was put to the test in Liz Earle laboratories it was seen as a weed. Now a project run by women that directly benefits 5000 indigenous women is keeping it alive.

A double blind clinical trial carried out by James' team saw staff receive samples marked either A, B or C. No-one knew which one contained the new ingredient - not even Liz herself.

The haircare collection, including a range of shampoo, conditioners and that hair oil, is back on the shelves.

The award-winning botanical beauty brand, originally set up by Liz Earle and Kim Buckland, celebrates its 20th anniversary this year. It has come a long way from its tiny base above a shop on the Isle of Wight.

Products, including the hugely popular Cleanse & Polish Hot Cloth Cleanser, are sold around the world after the company was acquired by Avon in 2010. It now employs more than 600 people in the UK and is sold online, in John Lewis and Boots as well as on QVC UK.

"I am enormously proud of Liz Earle Beauty Co and its incredibly talented and inspiring team. We decided to hand over the reins to a much larger organisation with business experience around the globe, to grow the brand and secure its future around the world," says Liz.

"The group chose Avon as it has a strong on-going history of being 'the company for women'. I'm still very much connected to the company and continue to work as a consultant and ambassador."

The brand's aims have never changed: to source the highest performance, quality naturally active ingredients that are safe and have a unique efficacy on skin.

Some formulations are preservative-free, but where preservatives are used they are usually relatively low concentrations of the highest grade, broad-spectrum formulas. Genetically engineered ingredients are never used and products are not tested on animals.

Visit www.lizearle.com.