I am not a fully sentient being. To those who have seen me first thing in the morning, this will come as no surprise. But in this case I am referring to the fact that I am congenitally anosmic; or, as I more helpfully put it when people thrust perfumed articles under my nose and invite an opinion on the aroma, I was born without a sense of smell.

It took until I was seven to convince my mother. She reluctantly acknowledged the truth of my claim ("Air! It's just air, mummy!") after making me sniff the fumes from her bottle of nail varnish remover until I looked up hopefully and said "My eyes are burning - is that what you mean?" Although I would still privilege that experience over the time I was persuaded by well-meaning schoolfriends that as I couldn't smell Emma Webster's perfume, I should drink it. This was, I recall, on the grounds that taste and smell are so closely linked that it would give me at least some idea of the delicious scent I was missing. Alas, all it taught me was that perfume is not a viable beverage, and all it taught the rest was that White Musk-laced vomit still smells, ineluctably, like vomit.

Max Christian, a fellow congenital anosmic, whose website (maxuk.net) has several pages devoted to the subject, had similar difficulties. "My first girlfriend's parents were industrial chemists," he says. "They didn't believe me either, so they gave me a bottle of concentrated hydrochloric acid, just to be sure. What they hadn't realised is that I would hold it right under my nose before trying to smell it.

"Apparently that's not something [normal] people would actually be capable of. Before anyone could stop me, I had inhaled enough fumes to keep all past, present and future members of the Grateful Dead happy for a week."

Naturally, the problems of being olfactorily-challenged don't compare to those which attend blindness or deafness, but certain accommodations do have to be made, which you only fully appreciate when you start living alone. I had enough sense to buy a smoke alarm, but it wasn't until my sister called round and nearly collapsed from the smell of a hob burner I had accidentally switched on that I realised I needed something that would alert me aurally to gas leaks before I blew up the street. The good people of Corgi eventually put me in touch with www.besltd.uk which sells such detectors. A few bouts of food poisoning alerted me to the fact that I can eat, unperturbed, food which would cause those with functioning nasal passages to don HazMat suits and call in the public health authorities. I now shop every two days, check best-before dates assiduously and treat three-day-old milk with the respect it deserves.

I have also learned to stock my shelves with visitors as well as myself in mind. So I have fruit teas in the house even though they appear to be nothing more than an expensive way of colouring a mugful of hot water, wine (variants on a vinegar theme to my useless palate, but people look bewildered when you offer them hot chocolate with everything) and herbs, even though they are a matter of supreme indifference to me. When I cook for other people and a recipe says "season to taste", I consult my written list of what green bits are supposed to complement which, add them until the dish looks decorated enough and hope for the best. I'm still mastering garlic.

My mother - possibly in an attempt to make up for earlier acetone abuse - used to smell all my clothes for me, but now I have to operate a strict rota and wash everything after I've worn it once. Occasionally, of course, the system breaks down, and for those who have had to sit next to me at work or on the tube at those times, I can only apologise.

On the other hand, I am a very good babysitter. I can't smell nappies or any of the preliminary gases that tell you something spectacular is on its way, so I have to watch my charges like a hawk for the brief cessations of activity and that faraway look in their eyes that tells me they are about to excrete something delightful. No kid is going to fall into a pond or lynch itself from a bunkbed on my watch. Although we may burn to a crisp if a fire starts out of eyeshot, of course.

I subscribe to the "what you've never had, you never miss" school of thought, as does Christian and many of the visitors to his site, but for those who lose their sense of smell later in life - through viral infections, nasal surgery or head trauma - the effect on their quality of life can be enormous. "I see a great number of people who are seriously depressed after losing their sense of smell," says David Roberts, ear, nose and throat consultant at Guy's & St Thomas's Hospital in London. "It's a very emotive sense, ingrained in us, in our pleasures - like mating and sexual desire - and in our warning systems. The nerves stimulated by smell send messages to one of the oldest, most primitive parts of our brain, which is why it's so integral to our lives."

Professor Tim Jacob at Cardiff University, who researches olfaction and had to start a second website when anosmics read about his work on the first one and started inundating him with requests for information, agrees. "You will have found other ways of adapting, using texture and consistency to get information about food. But other people get very disturbed [by the loss]," he says.

"The tongue can only distinguish the four basic tastes: bitter, sweet, salty, sour. Smell detects flavour and nuance, so they lose all significant sense of taste. About 17% become clinically depressed - they become oversensitive about having body odour, frightened of going out."

And those are just the obvious things. As Jacob also notes: "You lose lots of subliminal information and links with the emotional centres of the brain. Smells are inextricably linked with memories and form the backdrop to your sensory experience. They are tremendously evocative. The smell of your first girlfriend's perfume or boyfriend's aftershave, anything associated with strong emotion, will always trigger a rush of memory."

I am beginning to feel quite intrigued by this unknown world, but this quickly deepens into concern about what else I am missing. "And of course you are attracted to people who smell different from you, because it suggests they have a different immunotype," says Jacob. "It's the evolutionary system trying to get you to pass on two sets of immunity advantages to your offspring."

Galvanised by the thought of spawning only sickly, wizened mites, I ask about treatment. For those who have lost their sense of smell through infection or damage, the news is relatively good. "They usually regain some ability because the olfactory nerve, unlike the rest of the dozen cranial nerves, is capable of regeneration," says Roberts. Steroid-based drug treatments can help further. Nasal polyps causing blockages to olfactory passageways can be treated medically and surgically. But, as one might expect, less can be done to rectify congenital causes.

I will have to soldier on, and draw what comfort I can from a recent exchange with an ex-boyfriend who, as we reminisced about our relationship said wistfully, "You were the best girlfriend in the world. You let me bring curry home from the pub every night and I could fart as much as I liked." I'm putting it in my next personal ad.