Being called Pizza Face and having your complexion likened to a dot-to-dot puzzle is traumatising for teenagers, and wishing for the day they grow out of it has become an adolescent pastime. So having to endure the agony of acne in adulthood is a particularly heavy cross to bear.

But it's a growing problem. Adult acne - which now affects 20% of adults in the UK - is especially on the rise among high-flying women. According to the Acne Support Group, 5% of them get their first serious attack in their 30s or 40s. The spotty skin of Cameron Diaz, Britney Spears and Victoria Beckham, among others, is testament to the findings.

And it's not just a superficial problem. The psychological effects of adult acne can include a severe lack of self-esteem, social isolation, increased unemployment and even, in the most vulnerable sufferers, thoughts of suicide.

But why are more and more grown-ups being brought down by the problem? "We don't know, to be absolutely honest with you," confesses Professor Keith Holland of the department of microbiology at Leeds University. "It hasn't been resolved, but a large group of scientists are absolutely fascinated by it. If we could solve that, we could solve a lot of unanswered questions about acne. There's no rational explanation that everyone agrees with."

Acne at any age is triggered by hormones rather than by eating fried food, chocolate, smoking or a lack of hygiene as folklore would have it. It is caused by an abnormal response of the skin to normal levels of androgens, male hormones found in men and women, which control how much oil, or sebum, is produced from the sebaceous glands. These glands occur mainly on the face, back and chest, which are therefore the main sites where acne appears.

One of the possible reasons that adults experience the onset of acne - even if they were clear-skinned throughout their teens - is stress.

"My personal view is that stress is an important factor in acne," says Professor Holland. "We always see people's grades of acne worsen in May, which seems to be to do with exam time."

Stress exacerbates the problem by triggering the body's adrenal glands to become overactive. This in turn boosts sebum production.

Hormones are also the culprits when it comes to the onset of acne during pregnancy, because of polycystic ovary syndrome and in women who have recently stopped taking the contraceptive pill.

Other causes include alcohol and drug consumption, which can reduce the capability of the immune system and make adults vulnerable to spots, while cosmetics have also been shown to clog pores. Adult acne sufferers often get depressed, wondering if teenage angst has come back to taunt them. But two new treatments have excited dermatologists and brought a chink of hope.

The first comes from Dr Tony Chu, consultant dermatologist at the Hammersmith hospital and president of the Acne Support Group. He used single five-minute doses of laser treatment on 31 men and women with mild to moderate acne who had failed to respond to conventional drugs, and compared the results with a control group of 10 people given a sham treatment. After 12 weeks, 18 patients had lost at least half their spots and 10 had lost them altogether.

Dr Chu explains the findings by suggesting that the wavelength of light kills the bacteria, having a collagen-producing effect. In other words, the energy of the light targets blood vessels in the skin and fools them into thinking there has been a wound. The collagen then produces a wound-healing response.

Why this turns off the acne "switch" is still unclear, but Chu believes that the laser treatment effects a biological change in the reactivity of the skin.

It's a significant breakthrough. But Chu acknowledges that more work and larger studies are needed to confirm the findings. "It isn't a cure," he says. "What it does is manage and control acne."

At Leeds University, frustration at the ineffectiveness of antibiotics in the treatment of acne has led to another new approach. Professor Holland explains: "The reason people like us are looking for other treatments is the failure of antibiotic treatments.

"Treatment times for antibiotics are very, very long - between 12 weeks to two years - and that promotes resistance. Think about it - treatment for an infection is usually only seven days.

"We're working on something at the moment which we believe will come as a breakthrough. We have identified a virus that attracts the organisms associated with the inflammatory side of acne. A virus has been found on human skin which kills the organism, so instead of antibiotics we may be able to use viruses to help get rid of the disease. However, I have to say that it's early days yet."

These treatments may help in the future. But that won't help if you're desperately trying to get rid of the sore, scarlet volcanoes that are threatening to erupt just in time for Saturday night's big party.

Many beauticians offer "extraction", which is salon-speak for easing out blackheads in a haze of steam and expensive lotions.

But even if nothing else works, pick spots at your peril. Trying to gouge out your blackheads will force the contents deep into the skin rather than on to the surface and can lead to scarring or cysts. By adulthood, most acne sufferers have learned that squeezing a pore plugged by a blackhead only leaves the way open for another.

If you feel that you absolutely must extract your blackheads, invest in a comedone spoon or a blackhead expressor - a tiny device with a needle-eye end that inflicts fewer traumas on skin than eager fingers and is available from most chemists and the Body Shop.

Still, few of us can resist the urge to pop, and that little flash of satisfaction on the successful expulsion of an intruder is perhaps one of acne's few pleasures. So if you are going to do it, at least make sure you do it properly. According to the Acne Support Group, the best way to proceed is this: first wash your hands, then puncture the surface of the pustule with a sterilized needle, before gently squeezing out the pus. But know when to stop - if you see blood, you may be left with a scar.

· Acne Support Group: Alison Dudley, PO Box 9, Newquay, TR9 6WG. Tel (0870) 870 2263. Website: www.stopspots.org