The Instagram Love Your Lines page. Picture: Website screenshot

London – Standing in the bathroom at her parents’ home, Jill Gardner contorted herself in front of the mirror, the better to see the rear of her body. Had she really just spotted angry, purple stretchmarks all over the backs of her arms and calves?

But Jill wasn’t a new mom whose body had suffered the ravages of pregnancy – she was just 13 at the time. Now 40, she has never come to terms with the stretchmarks that have blighted her fair skin, and her life.

‘They were a legacy of growing from 5ft 4in to 5ft 11in in the space of two years,’ says Jill, a health and fitness consultant. ‘I have always covered my legs and arms as a result, and have loathed myself because of how ugly my stretchmarks look.

‘They badly affected my self-esteem and I still look in the mirror and feel ashamed. As a child, I felt like the only person on the planet who had them, and that I was a freak.’

Yet Jill is far from alone. For while stretchmarks remain the last taboo for many women - as loathed as cellulite but far less talked about – the truth is around 90 percent of women have some.

Even models aren’t immune. Model and new mom Lara Stone recently posed nude for photographs that clearly showed stretchmarks on her breasts.

While they are usually associated with pregnancy, stretchmarks can develop at any time, on anyone. Many develop during puberty, while some spring up as the body ages or changes.

A campaign was recently launched to show that stretchmarks are extremely common - and that a body can still be beautiful with them. Love Your Lines, launched on photosharing site Instagram by two anonymous mothers, is dedicated to celebrating stretchmarks.

Within weeks it had amassed over 84,000 followers and caused many women to post photos of their stretchmarks and reveal the stories behind them.

The aim is to bring attention to an issue that leaves many depressed about their bodies.

Women like Jill who, despite being a slender size 10-12 throughout her adult life, has hidden her body away for decades.

‘At school, girls weren’t allowed to wear trousers so I had to wear long skirts and socks pulled up to cover the stretchmarks on my legs,’ says Jill, a divorcee who lives near Milton Keynes with her children Gracie, 16, and Alex, 15.

‘You wouldn’t see me without a T-shirt on holiday, and at university I never wore strappy tops on nights out like the other girls. I felt so alone and I couldn’t talk to anyone about it.

‘I was shy with men and as I got older the idea of being intimate filled me with horror.

‘I met my first boyfriend at 18 and when we slept together - with the lights off - he seemed oblivious to my stretchmarks. But it didn’t alter the fact I couldn’t bear anyone to see me naked.

‘At 19, I saw a plastic surgeon to ask if he could cut away the skin on my arms. He told me the scarring would be worse.

‘Thankfully my ex-husband, Adam, an IT consultant, was always complimentary about my body and could never understand my self-loathing.’

So what lies behind these distinctive marks? They are caused by a weakness in the elastin and collagen fibres in the middle layer - the dermis - of the skin, says Dr Nick Lowe, spokesman for the British Association of Dermatologists.

‘The fibre of the skin either breaks or stretches, or both, resulting in these characteristic shiny ripples on the surface of the skin,’ he says. ‘More research needs to be done to understand what causes them but certainly weight gain and loss, growth spurts and big changes in hormones at different stages in life, such as puberty and pregnancy, are major factors.

‘Genetics may also play a part, making some women more prone even if they don’t gain much weight while pregnant, for example. Meanwhile, others may gain lots of weight and get none. But whatever the cause, stretchmarks can have a hugely detrimental effect on a woman’s confidence.’

They certainly led Joanne Hales, 35, an accountant who lives in Stoke-on-Trent with her son Ben, 15, to suffer from low confidence. She has been wary of what men might think of the lines that have covered her tummy since pregnancy.

‘There are days when I look in the mirror and hanker after the smooth stomach I had before I fell pregnant,’ she says. ‘I was young and naïve and used pregnancy as an excuse to eat Mars bars and cream cakes, ballooning from 10st stone to 14st.

‘When I gave birth, I didn’t have a single stretch mark, but within weeks - having lost the weight very quickly - my stomach was so lined it looked awful. No one had warned me that stretchmarks often don’t appear until after you’ve had your baby.

‘My husband never mentioned them, but we separated when our son was seven and I dreaded being intimate with anyone new because I hated the marks so much. I assumed men would be put off.’

Joanne says the first time she had sex with a new partner was ten months after her marriage ended. ‘I made sure it was in the dark – even now I prefer to have sex in the dark, so a man can’t see my stretchmarks,’ she says. ‘Since then, I’ve always mentioned the marks before getting intimate with anyone because once I’ve blurted it out, I can relax.

‘I probably mention them more than I should, but I can’t help it as I hate them so much.’

Similarly, when Jill’s marriage ended three years ago she was terrified her stretchmarks would affect her ability to find new love.

Jill says: ‘I felt I’d been very lucky with Adam being so complimentary about my body and worried that a new partner wouldn’t be so accepting.

‘It took me eight months to summon up the courage to go on a date, and then I thought about my stretchmarks all the time and the reaction they might get.

‘When I have been intimate with men, I find myself scrutinising their face for signs of repulsion. It’s been a surprise that, so far, I haven’t had any negative comments.’

While women like Jill and Joanne would love to be rid of their stretchmarks, a cure remains elusive, despite a massive industry of lotions and treatments claiming to diminish their appearance.

‘Once you have them, you won’t get rid of them,’ says Dr Lowe. ‘So be wary of products, treatments or practitioners who say you can.

‘The mass-market cosmetic creams and oils that claim to prevent or diminish stretchmarks will just improve the appearance of your skin by moisturising it.

‘There are a number of topical Retinoid treatments - vitamin A-based products, including Retin-A and Zorac – which have been scientifically proven to help. When applied directly to the stretchmarks, they help stimulate the production of new collagen to plump and tighten the skin and thus improve the appearance of the lines.

‘But they must be used under the supervision of a dermatologist and absolutely must not be used during pregnancy – too much absorption can be harmful to the baby.

‘Other options include fraxel laser or radiofrequency treatments, which again tighten and improve the appearance of the skin by stimulating the production of new collagen and elastin.’

But there may be hope for moms-to-be who want to try to prevent stretchmarks. A £70 tummy support claiming to banish them for two out of three pregnant women is to go on sale soon.

Women would have to wear the Secret Saviours band during the day from about 12 weeks into their pregnancy. It is said to work because it dissipates stress points over the growing bump, which makes it more difficult for an internal tear to spread down a straight line and turn into a stretchmark.

Zoe Staveley, 30, was desperate for a treatment after ballooning from a size 8 to 16 during her first pregnancy left her stomach looking like ‘a road map of London’.

‘Ninety per cent of the lines appeared during my first pregnancy, when I was only 18, and I believed that because I was young I could eat what I liked and my body would snap back into shape,’ says Zoe, a support worker for adults with learning difficulties. ‘By the time I gave birth, my stomach, calves, thighs, hips and boobs were covered in lines. At the time they didn’t bother me – I saw them as a badge of honour that I was a mother. But I soon began to dislike them – they left my body unrecognisable.’

When the relationship with the father of her daughter, Kodi, now 12, ended, Zoe was worried about meeting someone new. ‘One boyfriend said “Ugh, what’s wrong with your stomach?”, which knocked my confidence for a long time,’ she says.

Zoe spent hours searching the internet for a cure, but had to accept they weren’t going to disappear. Instead, she concentrated on slimming down from a size 14 to a size 8.

‘When I met Darren, who’s now my husband, I was really worried about the marks and for the first six months I always kept the lights off because of them,’ says Zoe, who lives in Dover with Darren, 29, who works for a fencing company, and their daughter Erica, four. ‘I’d also make sure I got dressed while he was still sleeping so that he didn’t catch sight of my body in daylight.

‘But he’s never mentioned my stretchmarks, and if I comment on them he says he loves me whatever my body looks like.’

Housewife Emma Hunt, 35, from Alsager in Cheshire, was terrified pregnancy would ravage her body. Her back and hips were already covered in silvery lines from puberty, after she suddenly shot up to 5ft 8in tall. ‘Thankfully, they’re are on the back of my body, which means I can ignore them,’ she says. ‘But when I’m wearing a bikini on holiday, people sometimes point them out and it’s embarrassing.

‘When I became pregnant with my son, George, who’s now four, I was paranoid I’d get them on my stomach. I would have been devastated. I stockpiled everything from cocoa butter to Bio-Oil, determined to do everything I could to prevent getting any more.’

Her midwife had warned that a woman can often get through pregnancy without any stretchmarks, but then they appear as soon as the bump has gone down. ‘I thought: “Please, no!”,’ Emma says.

Astonishingly, given her pre-disposition to stretchmarks, she didn’t gain a single one while pregnant, something Dr Lowe says is surprisingly common.

‘The reason some women get them in puberty and not in pregnancy, or vice versa, is down to a shift in the hormones oestrogen and progesterone, which affect how the structure of the skin behaves,’ says Dr Lowe.

It all goes to show that it’s impossible to predict if you will get stretchmarks.

Emma adds: ‘My tummy has always been flat, taut and probably my best feature. To lose that would have played havoc with my confidence.’

That is something many women know all too well. For the sad reality is that while positive body image campaigns may help to shed light on the scourge of stretchmarks, the lines continue to have a devastating effect on self-esteem and body confidence.