Ridiculously, I worried most about what others might think, or say. Before, when I told people that I have a 23-year-old son, they'd reply with mock horror: "No way! Were you, like, 14 when you had him?" Now, I feared they'd say: "So, your other son must be 30?"
When a man stopped me in the street to ask for directions, I thought it was because I looked like I'd been around long enough to know. When I saw my reflection in the car door, I had unconsciously started walking slowly and with a stoop, until I snapped myself out of it.
I thought it would be my just-teenage son who would be the most contrary - embarrassed to have a grey-haired mum. His reaction when he saw it?
"So what? I've got orange hair and I deal with it."
We have no choice about our natural hair colour, created by the pigment cells in our hair follicles producing melanin, which colours our skin, hair and eyes. But the cells in our hair follicles eventually die and, without them, hair is almost transparent and looks grey. But it doesn't mean we're old.
Researchers are finding we're losing our colour much younger, and a third of women in the west discover their first grey hair before they're 30.
Genetics tend to determine at what age the first grey will sprout. But smoking, poor nutrition, a lack of vitamin B12 and thyroid problems can help speed that along.
My genetic lottery could have gone either way: my mother's hair began to turn grey when she was 19, but most of my father's hair - at 75 - is still silky black. No need to guess whose genes I drew.
Since my late 20s I had hidden the greys beneath hues of chocolate brown, brassy auburn, and even once an alarming electric blue-black, both through professional colourists in salons and messy home jobs in the bathroom. It was time-consuming, smelly and expensive.
On the plus-side, it made me feel younger (or at least my age).
I made the decision to stop only after suffering allergic reactions to hair dye. My eyelids swelled, my eyes burned for days, my scalp itched and the skin on my face was ultra-sensitive for a week. I felt nauseous and tired and, by the third time it happened, I connected each episode to having my hair dyed.
My mother suffered a similar reaction. One of my cousins had such a strong reaction she had trouble breathing, and my grandmother's face swelled violently in reaction to a dye.
We're not the only ones, it turns out. Hollywood actress Pauley Perrette, a natural blonde, dyed her hair ink-black to play NCIS's goth forensic scientist Abby Sciuto. But when she was hospitalised after her face swelled, Perrette tweeted a warning to her fans on the risks of dyeing.
A reaction to dye is not always immediate; you can use it for decades without so much as a tingle. Actress Pauley Perette tweeted a warning to fans when her face swelled. Photo/ @PauleyP via Twitter
So what does this to us, and why only some of us?
We can blame the chemical para-phenylenediamine (PPD), found in most permanent hair dyes, especially darker colours. It was banned in Germany, France and Sweden in the 20th century, and voted Allergen of the Year 2006 by the American Contact Dermatitis Society, which is no great compliment.
Professor John McFadden (no relation), an internationally recognised expert in contact dermatitis, wrote in the British Medical Journal that the incidence of allergic reactions to hair dyes is rising, as more - and younger - people dye their hair. In Denmark, 75 per cent of women and 18 per cent of men have used hair dye, most first using it as teenagers.
"Cultural and commercial pressures to dye hair and, perhaps, the widespread obsession with the 'culture of youth' are putting people at risk," McFadden says, calling for wider debate on the safety of hair dyes.
A reaction to hair dye is not always immediate; you can use it for decades without so much as a tingle. But when your body reaches its threshold for PPD, it will react.
Next time your head is exposed to hair dye, the reaction is likely to be stronger.
DermaNet NZ says mild reactions are dermatitis to the eyelids and ear rims; in severe cases, there is marked reddening and swelling of the scalp and face, and the eyelids can close completely. Anaphylaxis occurs in rare cases.
Most hair colour products carry a warning on packaging to do a patch test, behind the ear or on the arm, 48 hours before you use the dye. But, seriously, who does it? Especially when we've been using them for years without complaint. But because that sensitivity can develop over years, you should do the allergy test every time you're about to colour your hair.
My mother stopped colouring her hair more than a year ago. It is now the most stunning tone of silver. The funny thing is, people don't really comment on her new hairstyle; more how beautiful her complexion looks.
It's always intrigued me how, as women, we've grown up terrified of it, yet men can wear grey with distinction - George Clooney, Hugh Grant and even newsreader Mike McRoberts, who's now known in the corridors of TV3 as the Silver Fox. But then, men have their own cross to bear: baldness.
I'm easing my way into this colour transformation, with the help of a very supportive hairdresser and an understanding husband and family. I've started with a few golden highlights - I figure it's on-trend, like silver and gold cutlery - and the cut will always be short and funky. Jamie Lee Curtis is my muse.
I won't let my lack of hair colour determine who I am. I've just completed my first quarter marathon, got my day skipper's certificate and I'll wear short shorts if I want to. I am happier and healthier than I have been in 20 years.
People have told me I'm brave. But I had little choice. What anyone else thinks, I no longer care. This is me now, greys and all. It's much better than warts - or swollen eyelids - and all.
