In a year I shall have saved approximately £2,000 on hairdressers' bills and two weeks' worth of blow-drying time. That's the good news. The bad news is that I am bald. I have lost my crowning glory. To be honest, it was never exactly glory - more a sort of placatory mop, an agreeable and undemanding piece of furnishing. When I look at it in photographs, it seems to say, "Touch me, I'm soft. Trust me, I'm harmless."

And now it's gone. Last autumn, I was diagnosed with ovarian cancer. After a hysterectomy, I was prescribed a course of chemotherapy and told it was "99% certain" I would lose my hair. I clung on to that 1%. My hair was my first address to the world. I wasn't exactly proud of it, but I was pleased with it - pleased that my hairdresser made it look thicker than it really was; pleased that it never got a ratty, menopausal look.

I read all I could about hair and chemotherapy. There was the ice cap, a rubber hat filled with water, then frozen, which blasts cold air on the head during treatment and protects the cells from the effects of chemicals. But my treatment was long and the ice would melt. I tried an oncology hair specialist. "What are you to be treated with?" he asked. When I told him Taxol, he said he couldn't do a thing for me. Now it was down to handy hints. The most practical advised cutting my hair as short as possible, avoiding all colourants and harsh shampoos and washing it in cold water.

"Get a wig," my sister urged. But wig-buying seemed to belong to the damp-knickers world of old age and prosthesis. She hauled me into town anyway. My eventual purchase, a strawberry-blond bob, made me look like a French transvestite.

I got myself an army number-two cut. Actually, it didn't look too bad and although I think it pained my husband that his ultra-female partner had gone butch, kind friends flattered me and said I should keep the style when my hair regrew. I felt quite at ease with it; I had once had my hair cut like this when I was 19. As a young journalist, I was sent to interview Ireland's first unisex hairdresser. It was the era of huge Mary Quant eyes and false eyelashes and the boyish cut she gave me, tinted platinum blond, made my eyes look like dinner plates. It was the best look I ever had. There is a difference, of course, between 19 and now. No lovely stem of teenage neck, no razor jaw. Still, I felt quite smug. I no longer kidded myself that my hair would hang on for ever, but felt confident that it would last at least until after Christmas.

Two weeks before Christmas it began to fall out. At first I was completely grief-stricken. All the sorrows of my life seemed to gather in around this dismal shedding. When I woke in the morning, a sinister hairy nest lay on the pillow. If I ran my hand over my hair, I had hairy palms. And this wasn't even like normal hair. The strands that drifted seemed lifeless, dull and repellent.

I went to London with my sister to order a hand-made wig. On the way to the wig-maker, we stopped for coffee. The cafe had a mirrored wall and I became aware that a customer behind me had lost interest in her book and was staring fixedly at the back of my head. I jumped up from the table, dashed into the loo and held a mirror to the site of fascination. Alopecia had set in - but only at the back. I wasn't just going bald, I was going old-lady bald. Mangy bits of hair draped the back of my skull and a large, sad, naked patch showed through. Oh, what treachery that one's front should present a creditable image and one's rear betray one so spectacularly.

It was only two days to my next chemotherapy session. I made up my mind to get my head shaved at once, before post-chemo exhaustion set in. Back from London, I headed into town to visit a hairdresser. It was the festive season. The salons were frenzied with women having their own lovely, luxurious locks frosted or fretted or softly curled. I tried hairdresser after hairdresser. None could fit me in before Christmas. I was about to give up and go home when I sighted the candy cane sign of a barber's shop. It was empty but for the barber, a stocky young man with one earring. "Can you shave my head?" I blurted out. "I'm on chemotherapy."

He put a hand on my shoulder. "I done it for my mother," he said in his Dublin accent. As the razor buzzed, he kept his hand on my shoulder. It was a gesture of infinite kindness. When I had entered the shop it was empty. Now, four schoolboys came in and then a middle-aged man. The schoolboys stared in avid fascination. The man writhed in hideous embarrassment. I was committing the ultimate indiscretion. I was baring my skull. The naked breast, I was to discover, is far less shocking in a woman than the unfurnished head.

Back home, I tied my head up in a scarf and mentioned offhandedly to my husband, "Oh, I got rid of my hair."

There was a pause while he absorbed the fact that I was now officially a bald woman. "Oh, probably the best thing," he murmured mildly.

I wanted to howl and howl. I wanted to be hugged and consoled and assured that I would still be loved and accepted. But a part of me feared I could not be lovable. Best not to make a fuss, and just get on with life.

Armed with my new wig, I was able to face Christmas. I wore a knitted skull-cap at home, rather like the one worn by the Irish author Sean O'Casey in his eccentric old age. I quite liked this. It made me seem dotty rather than disadvantaged. Then I developed a rash. Heads aren't meant to be covered all the time - particularly in indoor temperatures. I joined the world of women in Sound of Music-style bandannas.

Although my face is no longer young enough to make me a beautiful bald woman, like Sinead O'Connor, my skull is really quite handsome. It is high-domed with a large bone mass at the back that looks like a taut pregnant belly. Under that is the soft, shadowy nape of the neck. The skull is the one part of the body that stays youthful, that does not get lined and old. For although bones grow brittle and the body slows down, the life of the mind is always active, from the first infant recognition of light and sound and colour, to the amazing development of a child's imagination, to the dreams and sexual fantasies of teen years, to the ambitions and achievements of adulthood.

Years ago, I had a conversation with a spiritual healer. I asked him what he believed and he said he considered himself to be a part of a universal consciousness. I told him I believed in individuality and that I myself was strongly defined by my work as a writer, and I liked it that way.

"But suppose you were in an accident," he said. "Suppose you could no longer move or speak or write, although your brain remained the same. Then, who is Clare?"

Now I could no longer write. I was too tired and chemotherapy sets a scrambler on the intellect. My most feminine and sexual signatures, my hair, my womb, my ovaries, had been removed. Who was I? But the question struck me with curiosity rather than fear.

In spite of my own optimism, I never quite had the courage to go out in public without my hair. "What's the problem?" I challenged myself. But heads don't get the tan and shine of those parts of the body exposed to the weather. It is the pallid, underwater look that makes them seem so odd and vulnerable. I kept my head covered in public places, but it seemed to me worse than a compromise. I preferred my hairless head to the scarves and wig I wore. The range of cancer accessories is dull at best and limited by one's own lack of mobility. To get a good wig you need friends and determination and courage. Most people being treated with chemotherapy feel too beaten to do the rounds of the shops. The head-coverings sold to cancer patients mostly have a sad, "this'll do" feel.

Just 10 years ago, this is how it was for pregnant women. They buried their shameful bulge in a shapeless smock. They stuffed the hapless infant up under a jumper so that "ordinary" people would not be shocked by the sight of a child feeding from its mother. Now, mothers polish their bumps with oil and display them proudly to the world. It only takes a little pioneering, an imaginative make-up artist or headwear designer, to banish the stigma of cancer baldness.

Some years ago a glossy magazine published a computerised mock-up of famous women without their hair. The one who showed up best was Barbra Streisand. Her bold eyes, her striking mouth and nose looked beautiful without a softening frame of hair. Her direct and humorous gaze were given full measure. She actually looked sexier - but tougher.

Charlotte Brontë suffered agonies over her plain appearance (a Victorian earphone of ringlets did little for her). Many eminent women were considered plain because a lot of frothy hair made their thoughtful faces look silly. George Eliot's strong, intelligent face was humiliated by its mop of dry-looking curls, as was Elizabeth Barrett Browning's. Without their hair the world's gaze would have been directed to their amazing brains rather than to a set of features that scored poorly on the beauty barometer.

I'm not advocating a Shave the World movement. I have just finished chemotherapy and have been told that in six weeks my hair will begin a tentative resprouting. I will welcome it back. But I am grateful to have made acquaintance with this naked self. As a baby's hairless head is tender, a woman's is arresting. It says, "There is more to me than the sexual female. I am my own woman - a thinker, a dreamer, a voyager, a survivor."

· Clare Boylan's novel Emma Brown is published in paperback by Abacus today. To order a copy for £6.99 with free UK p&p, call the Guardian Book Service on 0870 836 0875.