It's hardly an activity that everyone would be comfortable with (to say the least) – but some women are making hundreds every month, simply by selling-off their used underwear. 

Indeed, the likes of pantydeal.com, which describes itself as a "market for used panties," facilitates both buyers and sellers – and says it's busier than ever.

"How would you like to make good money from worn panties with a resale value that is far higher than the original price?" the US-based website asks.

"The product requires no extra marketing, manufacturing or storage space – just wear your panties as normal and then sell them for a substantial profit to one of our fun loving, adult panty sniffers."

And now one advocate of the practice has spoken candidly to the New York Post, explaining why she first got involved. 

"It all started in January 2015, after I damaged my shoulder helping a friend move. 

"I had to give up my waitress jobs because I could no longer hold the trays. Another server confided that she occasionally sold her underwear for cash. I was intrigued."

The unnamed businesswoman, who is single, currently charges a fixed price of €13.50 per pair of knickers or tights.

That includes 48 hours of wear. Additional days of wear are available at €4.50 per day, though she'll only go up to four days in total.

The young woman says she buys her underwear in bulk for just 25c a pair so she makes about €55 a week profit, a sum "which helps pay my share of the utility bills".

She explains: "My first deal went like a dream.

"A guy messaged me about a pair of panties he’d seen on my page. He wanted me to wear them for 24 hours, and to not masturbate in them (most men actually want you to do that).

"He paid me via PayPal within 20 minutes, and I shipped the undies off via USPS in a Ziploc bag and a discreet brown envelope."

She continues: "The more info you share about yourself, the more popular your products, and the more you can charge.

"There’s no way I would show my face, because it’s not worth jeopardising a future career.

"But I will send buyers a digital picture of myself – waist-down only – wearing the panties they’ve bought."