“If it’s a choice between electricity, snacks for the kids, or sanitary towels … Even that £2 at the end of the month matters,” says Kerry, from Aberdeen.

The 35-year-old is raising three teenagers alone – a daughter and two boys with autism. She doesn’t need to explain what gets sacrificed as she chooses between food, heating and other essentials for the children, and sanitary products for herself.

Kerry used to have a wage coming in – she was a home carer for disabled and older people – but four years ago had to give up work to care for her boys. As she struggled to apply for benefits, her financial difficulties “snowballed”, and having a period became another cost she couldn’t afford.

For a year, in order to pay the bills, Kerry went without any sanitary products at all. Instead, each month she would stuff toilet paper into her underwear. Often, she would just stay in the house and not go out. “Y’know, to be near the toilet,” she says.

The only reason Kerry has pads now is because of a local food bank, the Aberdeen City Food network. She’d started to volunteer last Christmas – giving out food parcels to the city’s most deprived areas – and one of the female organisers quietly asked if she needed any “girly bits” herself.

She has no idea what she’d have done otherwise. “How do you even say to someone you haven’t got £2 for tampons? How do I verbalise it?”

Worker Kerry Wright and client Kelly Donaldson at the Community Food Initiative food bank in Aberdeen. Photograph: Murdo MacLeod/The Guardian

Period poverty is in many ways the hidden side of British inequality: women and girls in one of the richest societies in history stuffing socks inside their underwear and being trapped in their homes each month.

It isn’t hard to see why sanitary products are often out of reach. Research shows pads and tampons cost women around £13 every month. Add another £8 for new underwear, and then almost a fiver for pain relief. That means women need to find more than £300 each year for periods – or the equivalent of a fortnight’s rent.

Women having toiletries for menstruation isn’t discretionary but essential healthcare

The problem isn’t a new one. As a teenager, Kerry herself didn’t have access to sanitary products, missing chunks of school as she waited out her period at home. But, as she puts it to me: “Twenty years down the line, I’m still seeing it.” In a climate of shrinking wages, cut benefits and rising living costs, period poverty is rearing its head with new prominence. Increasingly, food banks are reporting women coming in needing donations, and being ushered into a back room lined with boxes of tampons.

Charities typically charged with donating sanitary pads to Kenya are now being called to Leeds; swaths of girls are missing school because their parents can’t afford pads. The scale is such that the Labour party pledged last week to commit £10m to ending period poverty in schools in England. Scotland is already piloting offering free sanitary products to women and girls, via the same scheme that Kerry now relies on.

But period poverty is only part of the picture. Hygiene poverty – where families are unable to afford essential products such as shampoo and deodorant – is quietly spreading. As destitution grows, dignity is now a luxury item. One charity alone, In Kind Direct, distributed £20.2m of hygiene products in 2016 – up almost 70% on the year before. Trussell Trust research with the University of Oxford found that more than half of the households visiting the network’s food banks this summer are now struggling to afford toiletries as well.

There is something glaringly symbolic about this. Sweat stains. Dirty hair. Blood on your underwear. It’s literally marking certain people out, with poverty seeping into their skin.

When Labour announced its commitment to fund sanitary products for low-income school pupils, it signalled more than a pot of money. It was a message that women having toiletries for menstruation isn’t discretionary but essential healthcare; that, as austerity measures exacerbate hardship for the poorest, it is the state’s duty to provide a safety net for a human being’s basic needs.

Britain is witnessing the growth of poverty at its most debilitating: isolating, shaming and lasting. For any politician who doubts the need to address this, Kerry’s parting words are worth remembering. “It leaves you with an anxiety. Even once you get access, you worry it will happen again.” She pauses. “The impact stays with you.”

• Frances Ryan writes the Guardian’s Hardworking Britain series