Ms Guille said she felt "yucky" when she saw the messages.
When Alison Guille's daughter finished primary school forever, she wanted to get rid of the dresses and tights that had been laying around the house for years.
But the Sydney mum didn't want to just throw them in the bin, so she took to Facebook in search of someone who might want to buy them. They were only worth about $5 and she thought they would be sold in a heartbeat.
However, within days she was inundated with perverted messages which left her feeling "yucky" and worried about selling clothes online.
She posted an innocent advert on a Sydney buy, swap and sell page in May along with a photograph which showed a small bundle of dresses and tights — which were suitable for a girl aged between 10-11.
However, she looked at her phone about two days later and found a number of strange messages from a man with a cartoon picture as a profile picture, who asked numerous questions about the children's clothing.
"I blocked him because he wanted pictures, up-close, of the crotch area to 'make sure there was no rips or holes,'" the concerned mother told news.com.au.
"He wanted to know how often she had worn them and if I had washed them."
She said the questions felt very strange, particularly because it appeared — from the man's Facebook page — that he didn't have any children.
"I said: 'Of course they are clean. I wouldn't sell dirty things' and thought 'that's strange'" she said.
"When he asked for pictures I felt like he was a pervert and there was no way I would take pictures like that. It's like violating my child's privacy. And it was just so strange to have all these questions for about $5 worth of tights.
"And, when he kept insisting on me sending him pictures to make sure they were in good condition, I decided there is no way, as a mum, I could let him collect from my home or, in fact, even have something that had been so close to my child's private parts.
"The questions kept coming even when I wasn't replying. It was so strange so then I blocked him."
However, just a few hours later she began to receive more strange messages, this time from a "woman" who wanted to post her the tights for $10 and "refund" her 30c because the postage was $9.70.
But what creeped her out was how the woman said the blue tights were impossible to buy in shops, which wasn't true — you could buy them anywhere.
Feeling uncomfortable, Ms Guille just gave up and said it just wasn't worth the hassle but the creepy messages from the man — who later deleted his profile picture and changed his name — made her wary when selling clothes online.
She said she didn't report it to the police because she hadn't given out her address and the man had disguised themselves online, but looking back, she wishes she had at the time.
"It left me feeling really yucky about the process of selling and now I'm more careful about who I allow at my house to collect items and offer to drop off (if) I feel they don't seem legit," she said.
"I will never sell underwear or swimwear after that."
It comes after a man with a zip fetish has approached at least six women selling clothes on social media in Sydney — asking them oddly specific questions about how the zips on their clothes taste.
Ms Guille said she had been sent many bizarre messages through selling clothes on social media, but added they were normally harmless and it was all part of the fun of it.
"The whole selling thing is just a strange experience all around," she said. "I've met some lovely people and some very strange people. It's entertaining."