Sadly this isn't always the case, as I know only too well. Having sailed through adolescence with barely a zit, I had smugly assumed that my skin was unassailable. Until a year ago, when a vague itching suddenly blossomed into a body-wide case of eczema.
Out went biological washing powder, scented fabric softener, perfumes and soap; in came cleansing bars and water, but to no avail. My doctor diagnosed "adult-onset eczema", and prescribed steroid creams, adding that the condition was "very rare". When the creams had little effect, he sent me to a dermatologist who prescribed more and stronger creams.
But are adult-onset skin problems so rare? I was amazed by the number of my girlfriends in their early thirties who admitted that their skin had never been so bad as it is now, even in the worst throes of puberty. I was reluctant to use steroid creams for any prolonged period because they are known to thin and irritate the skin in the long term. But when you're afflicted with a hugely obvious glowing, flaking, burning patch of skin right on the front of the neck, a beacon which visibly transfixes anyone you speak to, you do tend to want some kind of treatment.
According to Prof John Hawk, consultant dermatologist at St Thomas' Hospital in London, adult-onset eczema is relatively common. "The older you get, the more likely you are to get one form of eczema or another, because the skin is drier," he says. "In the short term it usually reacts well to intensive moisturising. Eczema is probably caused by an allergic reaction to something on the skin - cosmetics, jewellery, perfumes, nail varnish and hair dye can all cause it."
The conventional remedy - hydrocortisone cream - is, he says, "very weak and unlikely to cause any harm. At higher strengths it can cause thread veins and fragile skin, but that is after long-term use - a few days every so often won't cause problems". But, he says, such creams treat the effect, not the cause, of the disorder. Other problems such as acne are rarer in older people, and are likely to be inherited or down to a hormonal problem.
Skin specialist Helen Sher says that she sees lots of women in their thirties with problem skin. "I actually call myself a skin psychologist, because skin problems can be so depressing. People can even become agoraphobic because they don't want anyone to see them."
The Sher system is a range of products that are designed to be used together for maximum effect - mixing and matching with other ranges is not recommended. "If you are baking a cake and you leave out two ingredients, you won't have the cake you wanted," says Helen. Sher products are particularly effective for acne.
Every Sher client fills out a detailed questionnaire that deals not only with skin but also with lifestyle, and is prescribed an individual selection of products for their particular skin type. If, like me, you are diagnosed with dry and sensitive skin, you need an oily pre-cleanser, a gentle toner, foaming facial wash, moisturiser and extra-rich moisturiser. And the key to the system is rinsing with warm water - splashing 20 times each night.
Helen, who is 64 but looks years younger, also insists on a make-up regime. Wearing make-up might seem the worst possible thing for problem skin, but, she says, it is vital. "Your skin is exposed to everything - sun, rain, hard water. If you had a most beautiful Hermes handbag and left it in the garden, exposed to the elements, how long do you think it would last?"
She prides herself on her no-nonsense approach - "even women who hate wearing make-up like wearing this". So each morning, on goes the light foundation mix, powder and bronzing glow. Although her instruction booklet looks daunting, once the habit is formed the system takes about 10 minutes every morning and evening. All Sher products are completely natural and water based. Using steroid creams, says Helen, is "the worst thing you can do. They thin already fragile skin". And she is also wary of some strong drugs for acne - linked to cases of teenage suicide.
The holistic beauty therapist Bharti Vyas also says that adult-onset skin problems are in fact very common. "I am definitely seeing this more and more often," she says. "These are very distressing conditions because you can't hide them." Eczema, she says, is particularly rife.
"It's very common, particularly on the arms and legs, and very upsetting," she says. "It really shatters your confidence." Stress and diet, she says, are important factors. "I advise people to control their stress levels using techniques like acupressure. And diet is the most important thing - the body is what we eat, and when the body is complaining, it manifests itself in the skin." She does not recommend discontinuing conventional treatments. "I always tell people to keep applying their doctor's medication, but I teach them to wean themselves off it slowly," she says.
For eczema, the products she uses are a skin softener and body polisher, and liquid mineral salts to go in the bath. And for acne, and similar conditions, she looks particularly hard at diet and general health. "I am a great believer in vegetarian food - no meat or dairy products," she says. "It helps the elimination process, and constipation is related to acne. Once you start helping the detoxification of the interior body, you can also have a facial routine to deal with local spots." She believes that every condition is treatable and ultimately curable. "One thing I boast about is that I don't fail. If people stick to what I tell them they will get better."
My own scabbiness is on the way out, I think. It is finally responding to a regime that includes two litres of water a day (well, maybe one and a half), more fruit and vegetables than I'd ever have thought possible to cram down, a drastic reduction in wine consumption, avoidance of dairy products and red meat and sugar, plus the Sher system and Bharti Vyas products.
I'm not sure which has had the greatest effect but I'm most happy to carry on with the lot indefinitely, as long as my skin stays clear. After all, it's taken me a year and a half to get this far.
Helen Sher: 0171 499 4022. Website: http://www.sher.co.uk/skincare. E-mail: firstname.lastname@example.org.
Bharti Vyas Clinic: 0171 486 7910. Her book `Beauty Wisdom' is published by Thorsons at pounds 12.99.