An intriguing observation is that eczema rates have increased in line with sales of paracetamol. Paracetamol use has already been associated with an increase in asthma and rhinitis in young adults. Researchers at King's College London performed an analysis to see if there was any link between paracetamol sales and atopic disease prevalence in children and adults.

They used data from the International Study of Asthma and Allergies in Childhood (ISAAC) on the prevalence of four atopic symptoms in 13 and 14 year olds and 67 year olds in 1994-1995 as well as data from the European Community Respiratory Health Survey (ECRHS).

Not surprisingly, they found that paracetamol sales were high in English speaking countries. But what was surprising was that paracetamol use was positively associated with asthma, eczema and allergic rhinoconjunctivitis in teenagers, and wheeze and asthma in older individuals (Eur Resp J, 2000; 16: 817-23). The risk went up as the dose went up.

Even more intriguing is the hypothesis that the decrease in paediatric aspirin use (due to the risk of Reye's syndrome) in favour of paracetamol may also be a contributing factor. Aspirin, in contrast to paracetamol, sets off chemical reactions in the body that suppress immunological T-cell responses (Ann Allergy Asthma Immunol, 1998; 81: 347-51).

If all this seems too much to take on board, consider that atopy is much less common in children who live in somewhat less sanitary conditions such as farms (Clin Exp Allergy, 1999; 29: 28-34) and in those whose families are not obsessive about handwashing (see box, p 3). There is also growing evidence that children in large families where diseases get spread around early in life have less atopy (Thorax, 1998; 53: 28-32; BMJ, 1994; 308: 692-5). Also, children from small families who enter daycare at an early age also seem to get the same protection (Lancet, 1999; 353: 450-4).

Add to this the finding of a recent Swedish study, that children in families who follow an anthroposophic life style avoiding unnecessary antibiotics, having few vaccinations and diets which include live lactobacilli have lower rates of atopy (Lancet, 1999; 353: 1485-8), and the hygiene hypothesis begins to look increasingly sound.

Newer thinking is that if eczema is to be approached with any drug treatment at all, then drugs should seek to activate certain pathways within in the immune system to keep it from overreacting. Such therapy is similar to the desensitisation regime which homoeopaths have been advocating for years.

Studies are in progress to assess the effectiveness of a 'vaccine' that might do the job which natural dirt and diseases were supposed to do. Experiments based on animals given a vaccine based on Mycobacterium have been encouraging (Immunology, 1998; 93: 307-13) although, of course, it is difficult to draw firm conclusions about human health from animal studies.

You can't help but wonder whether a campaign to educate parents on the benign nature of most household germs and the benefits of childhood illnesses might be a cheaper and more effective way to protect future generations.

!APat Thomas