Today, her outfit is a shimmering low-cut bra with a matching ra-ra skirt in navy that exposes her belly button and stops just above her knicker-clad bottom. She wears black thigh-length boots with three-inch stiletto heels and sits on a high bar stool behind a counter that faces the large glass shop front.

It is a small interior which contains, apart from the bar stool, a fridge behind the counter and a television. The shop’s floor is raised a metre above the pavement outside and you enter the shop by walking up four steps.

Such an arrangement offers an unimpeded view of her legs, first, to even the most casual passerby. It is almost impossible then not to follow the legs up, quite naturally, to see the young woman herself.

She has a heart-shaped face and small eyes and nose that match her slight but perfectly formed figure. Her straight hair is long and dyed a rusty brown. She has skin that is pale and smooth, the kind that reminds you of babies; you want to reach out and touch it.

All day long and night, she perches on her bar stool and watches television, or smokes, or talks to a little dog. Her hands are busy, working on something small, roundish and green. Sometimes, she simply stares. Until a customer stops by, that is, drawn by the large flashing neon lights and signs with the Chinese characters, ‘man’ and ‘love’, and to what is being sold.

She is a bin lang xishi and she sells betel nuts.

The betel nut is the seed of the Areca Palm and the size of a walnut. It is, in fact, a fruit known as a drupe (other examples are peach and cherry). Grown and chewed over much of East and South East Asia, it is a mild stimulant with an effect said to be similar to that from smoking cigarettes or drinking coffee although euphoria and a pleasantly hot feeling are also common. Long-term use is addictive.

The betel nut has been cultivated and used in numerous ways beyond mere stimulant for thousands of years in Taiwan. It is Taiwan’s second largest agricultural crop after rice and, despite respected international studies linking its use to the single most important cause of oral cancer, production and use continue unfazed by the Taiwanese government’s efforts to arrest their growth.

To prepare it for chewing, lime paste is spread over a betel leaf which is then wrapped round the betel nut. It is sold in packets of 10 for NT$100 (£2.50). The nut is chewed, not swallowed, and the residual juice is spat out. Streets and pavements in towns and villages (but not usually the cities) across Taiwan are littered with splatters of this brown-red juice that stains the teeth, tongue and mouth, a graphic testament to its popularity.

What makes Taiwan unique from other betel nut-chewing countries is how the betel nut is sold. There are an estimated 70,000 betel nut shops - some no larger than a 2 metre x 3 metre booth - scattered throughout Taiwan which often contain nothing more than a young woman in skimpy clothing offering betel nuts for sale.

Mei Mei (not her real name) works in the betel nut shop next to my apartment which is located in a small but bustling town 65 km south of Taipei. She can be between 22 and 32 years old (she says her age is a secret). I see her almost every day sitting at her bar stool.

It is hard for me not to glance furtively at her when I walk past the shop: she is pretty and some of her outfits - selected from a specialist costumier - are extremely sexually provocative. Mei Mei is from Kaoshiung, a city in the south of Taiwan. She works shifts, either 7.00 am to 3.00 pm, or 3.00 pm to 11.00 pm.

Her mother had been a bin lang xishi for 10 years so it was not so unusual for Mei Mei to have chosen the same type of work; and she has been at her job for four years.

Now her younger sister is a bin lang xishi, too, at the same shop. Mei Mei earns between NT$50,000 (￡1,063) to NT$150,000 (￡3,191) per month, depending on how much betel nuts she sells. She says she enjoys her job and is good at it; she cannot imagine wanting to do anything else.

Beixin Lu is a main thoroughfare that runs for a kilometre along the northern edge of the town. There are over a dozen betel nut shops on this stretch of road alone. Many more are scattered around strategic locations to catch their main passing trade.

The customers, almost exclusively male, pull up in their loud trucks, their dusty scooters and their shiny cars. The young woman runs out to him. She smiles as she bends over to speak to him through the wound-down window of his car. Sometimes, she squats by the car and the man leans out of his window to speak to her.

After the exchange of words, she hurries back into the shop and returns with a packet or two of betel nuts. He hands her some money. Occasionally, she lingers before the car roars away. The young woman returns to sit on her high bar stool. Sometimes, the man walks into the shop for this exchange of betel nuts and money.

There have been many campaigns over the years to control or ban outright the sale of betel nuts in this titillating way, with reformers citing the practice as indecent and demeaning to the young women whose job it is to attract the customers. All have failed against a powerful lobby of Areca Palm businessmen and growers, which include entire mountain communities who rely totally on its cultivation for survival.

Not all betel nuts are marketed this way. A middle-aged man sells his betel nuts in a booth near the centre of town. It has been a family business for several years. Some women sell betel nuts dressed in ordinary T-shirts and jeans. But the majority of betel nuts are peddled by a young woman who wears a bra and a ra-ra skirt and an expression that alludes, perhaps, to different times.

Words and pictures by Wah-Yin Rixon. Wah-Yin Rixon lives and works in Taiwan.