Some skin lessons are best delivered as stories, because children remember stories long after they forget instructions. This one is for reading aloud on a summer morning, with the science for grown-ups following after. It begins, as the best summer stories do, at a grandmother's garden gate.

Mira was seven, and she did not want the hat. 'Hats are for babies,' she announced. Her grandmother, who had the most interesting face in the family — soft lines around the eyes like a map of every smile — sat down on the step beside her. 'Let me tell you about my friend the tomato,' she said, and Mira, who knew a good beginning when she heard one, sat down too.

The story of the two tomatoes

'When I was your age,' Grandmother said, 'I grew two tomato plants. One grew under the big net that shades young plants; one grew out in the open, because I wanted it to be strong and brave. The sun in our valley is friendly in the morning and fierce at midday. My open-air tomato ripened fast — and then its skin grew tough patches and cracks, and by August it was wrinkled like an old boot. The shaded one grew slower, and stayed smooth and glossy right until picking day.'

'Your skin is a little like the tomato's,' she said, tapping Mira's nose. 'It remembers every hour of fierce sun, even when you forget. Not the morning walks and the playing in the shade — skin loves being outdoors. The burning hours, the red-shoulder days. It writes them all down in a secret notebook, and it reads the notebook back to you when you are my age.' Mira looked at the map of lines around her grandmother's eyes. 'Did your skin write things down?' — 'Plenty,' laughed Grandmother. 'Sunhats hadn't been invented as far as I was concerned. I would like your notebook to be mostly empty, that's all. Wearing the hat isn't being a baby. It's being the gardener.'

The science under the story

For the grown-ups: the tomato is doing honest work. Childhood is when skin is thinnest and most vulnerable, and research consistently links sunburns in childhood to substantially higher lifetime skin-cancer risk — the 'notebook' is real, and it is cumulative. The protective playbook for children is well established: shade in the peak hours, cover-ups and wide-brim hats as the first line, and a broad-spectrum SPF 30+ on what remains exposed, reapplied after swimming and sweat.

Babies under six months are a special case — direct sun and sunscreen are both to be avoided; shade and clothing do the whole job. And the most powerful intervention of all is unglamorous: children copy adults. A parent who wears a hat and applies sunscreen without commentary teaches more in a summer than every lecture combined.

Making it stick

Habits outperform rules. Keep the sunscreen next to the breakfast things in summer so it joins the leaving-the-house ritual; let children choose their own hat, because ownership beats compliance; name the shade-hours in family language ('tomato hours') so the concept has a handle a child can grab. None of this needs fear — the sun is not the villain of the story, the burning hours are.

Mira, for the record, wore the hat — a yellow one she chose herself, with a brim like a sunflower. And on the way to the beach she explained tomatoes, at length, to her little brother. Lessons that arrive as stories leave as stories, which is exactly how they travel best.