Kerikeri-based Cashman is originally from Bill Clinton country - Little Rock, Arkansas. She came to New Zealand via a circuitous route involving rafting on three continents, meeting husband John Sanderson along the way.
The couple settled in Queenstown, where she established a massage therapy and beauty care business, while continuing to work as a river guide in nearby Glenorchy - and becoming intimately acquainted with New Zealand's small, biting fauna.
"They're bad," Cashman says of the Glenorchy sandflies. "When you first move here, when you get bit, you kind of freak out and the bites get really welted up."
From pain sprang the first incarnation of Goodbye Sandfly. Cashman was no neophyte when it came to product formulation - she had created 25 products for her company, Essential Touch, which sold a range of natural beauty treatments.
"I made everything," she says. "I had the training in using the oils and I had so much passion for the idea that I grew my own calendula, harvested my own marjoram and thyme and herbs from the hills, and I sourced organic lavender and dried and mixed it in with the salts."
The birth of her first child, Helena, saw her concentrate on massage but, when the couple moved to another sandfly-plagued district, Karamea, north of Westport, she again started bottling her repellent for personal use and to meet customer demand.
"All of a sudden we're a business again," she says. "Two summers on the Coast and we realised that the product was just fantastic, there's nothing like it.
"When we watched our Karamea community adopt it as their own, we realised it's a product worth taking out to the whole country because it's really good."
Goodbye Sandfly has an almond oil base, supplemented by six essential oils, and is entirely naturally produced. "It's the preserving that's the trick and few natural products companies have cracked that," Cashman says.
She is no Colonel Sanders, however. She's prone to telling inquisitive people the exact formulation, much to her husband's consternation. After all, there is a lucrative family business to protect.
"People would email from Australia and I'd say, 'well, here it is, but please don't sell it'," Cashman confesses. "I think we'll give it away again ... because I believe in an open economy and there is no reason to have secret recipes."
When this anecdote draws a gasp, she says: "It horrifies my husband as well."
In 2008 Sanderson gave up his conservation work and threw his weight behind the sandfly business. The family moved to Kerikeri, where they created a garden and fruit tree grove on 2ha.
Key to the expansion of the business was the involvement of laundry powder manufacturer Quantum Pacific, which agreed to represent the company, leading to deals with all three Foodstuffs supermarket regions and Progressive supermarkets.
"Our biggest focus is grocery and that's been the key to our success," Cashman says. "We're the number-one selling natural repellent in New Zealand and we're growing. We're getting better-ranging support from the grocery stores and better shelf presentation."
Next week Cashman launches an online buying service on goodbyesandfly.com, and New Zealanders will get first shot at buying her book, before it is made available on Amazon. "Why Natural Matters is an invitation to people to take a look at the way they make decisions in their lives and to understand that living a more natural life can be fun, instead of duty," she says.
Early victim
"The most mischievous animal here is the small black sandfly which are exceeding numerous ... wherever they light they cause a swelling and such intolerable itching that it is not possible to refrain from scratching and at last ends in ulcers like the small pox."
- James Cook, 1773
