A Psoriasis affects about two per cent of the population at some time. It is most common in those aged 10 to 30 years old, so your daughter falls within the usual bracket.

However, since people in their teens and 20s tend to be self-conscious about their looks, psoriasis is all the more distressing on the face at that age - even without the physical discomfort it can often cause.

Most conventional treatments of psoriasis are aimed at improving symptoms rather than getting to the root of the problem. However, they come with a raft of risks, limitations and side-effects, so you may find it helpful to be forearmed with the facts.

Topical steroids are recommended where, as in your daughter’s case, the psoriasis covers 5 per cent or less of the body. They can take effect quickly, but come with a range of side-effects such as thinning of the skin, which can make the symptoms worse.

Tar creams, another commonly prescribed topical preparation, have fewer side-effects, but can take up to 12 weeks to work and are messy to apply.

Vitamin derivatives are based on vitamins A or D, but are not, as they may sound, naturally based substances. They often cause skin irritation and can only be used for a maximum of 12 weeks.

Systemic drugs are generally only prescribed for severe psoriasis. Cyclosporin, methotrexate, acitretin and hydroxyurea are the most widely used, but can cause hypertension, kidney damage, anaemia and reduced immunity. However, your daughter’s case sounds mild-to-moderate, it is unlikely to merit such a powerful treatment regime.

Biological drugs seek to stem the development of psoriasis by targetting the immune system as psoriasis is considered an autoimmune condition. These drugs seek out dysfunctional immune T cells, or the chemical messengers they release, to eliminate the psoriatic process at source.

However, these novel agents do have drawbacks: they need to be taken by injection; they are expensive; they must be used continuously to maintain any improvement; and perhaps most important of all, their long-term safety is still under evaluation.

The good news is that there’s a wide range of alternative treatments available. So, before taking your daughter out of school, it’s worth trying out some of the alternatives that have proved effective for mild-to-moderate psoriasis. But first, it helps to understand what’s caused it.

The rough, raw skin that characterises psoriasis is due to accelerated skin-cell division. These cells replicate more rapidly than the body is able to shed them - in acute cases, at 1000 times the usual rate - so they build up on the skin surface.

The problem originates not in the skin itself, but in the immune or digestive system. Irritable bowel syndrome, ulcerative colitis or Crohn’s could be the source of the problem, so check these out first.

In the case of immune dysfunction, skin cells super-generate and, as they migrate towards the skin surface, they act as if they are fighting an infection or healing a wound, hence, the resulting inflammation. The role of immunity explains why psoriasis often starts or flares after an infection such as a sore throat.

Assuming you have discarded the possibility of a gut problem, a sensible two-pronged approach would be to target both the immune system, where it starts, and the epidermis, where it surfaces.

The ground rules for boosting immune function basically cover diet and supplementation and, to a lesser extent, relaxation and exercise.

The woody vine Smilax sarsaparilla works via the immune system, and is especially effective against the plaque-forming type of psoriasis.

Natural topical treatments include oils and creams containing bee propolis (found to be anti-inflammatory and analgesic by pharmacologists at Cuba’s National Centre for Scientific Research), aloe vera (J Eur Acad Dermatol Venereol, 2005; 19: 326-31), chickweed (Stellaria) and evening primrose oil (Clin Exp Dermatol, 1994; 19: 127-9). Anecdotal evidence supports their effectiveness to varying degrees.

One WDDTY reader enthusiastically recommends virgin olive oil, applied twice a day, which may work. Indeed, when five psoriasis sufferers followed a dietary programme that included olive oil (as well as saffron tea and slippery elm bark water), the results suggested that this might be a useful form of nutritional therapy (Altern Med Rev, 2004; 9: 297-307). Other specific nutritional treatments may address the problem from the inside out.

The incidence of psoriasis among the Inuit Eskimos is significantly lower than in other populations, and may be due to the large amounts of omega-3 fats in their fishy diet. However, a trial of dietary fish-oil supplementation by dermatologists at the Bristol Royal Infirmary failed to show any improvement in psoriasis symptoms (Clin Exp Dermatol, 1994; 19: 127-9). But as fish oils have multiple benefits, especially for growing bones and brains, it may still be worthwhile increasing your daughter’s intake.

The incidence of psoriasis is also very low in Africa. Dermatologists at the Shiraz University of Medical Sciences in Iran believe this may partly be due to the high consumption of maize in the traditional diet. Unlike wheat, maize is rich in linoleic acid, another essential fatty acid generally lacking in the modern Western diet (Int J Dermatol, 2004; 43: 391-2).

As with fish oil, it may be easier to take linoleic acid in supplements as it may be difficult to get enough from food sources to have a demonstrable effect. There is also good anecdotal support for supplementation with other oils such as hemp, shark liver and evening primrose. You have little to lose by trying these in turn.

It is also worth trying an exclusion diet - cutting out or drastically reducing acid-forming foods such as red meat, alcohol and dairy works for some. This may improve gut health and speed up the elimination of toxins in the gut. A high-fibre diet is recommended for the same reasons.

Your daughter’s condition may also be stress-related. Given the social and academic pressures at this time in life, it is a common contributory factor.

Psoriasis may respond well to psychotherapy (J Am Acad Dermatol, 1996; 34: 1008-15). Meanwhile, your daughter may wish to contact the UK Psoriasis Association, which is currently conducting a survey of teenage sufferers and offers support on its website at www.psoriasis-association.org.uk. The site also includes some brief advice on bullying.

Finally, in tandem with any of the above, your daughter could try increasing her water intake and sun exposure. In moderation, the sun’s ultraviolet B (UVB) rays can improve psoriatic symptoms (Exp Dermatol, 2004; 13: 764-72), though too much can aggravate symptoms. Drinking more water seems to help and will certainly do no harm.