High consumption of acetaminophen, the active ingredient in Tylenol and other products, might increase the risks of asthma and help to partially explain why it is so much more prevalent in English speaking countries than elsewhere.

In a report published earlier this year Dr. Seif Shaheen from King's College, London, and colleagues had suggested that asthma is linked to acetaminophen use in adults (Thorax 2000;55:266-70). Now, the same research team has just published additional findings, reinforcing the earlier results.

• Researchers performed an ecological analysis to investigate if asthma and other allergic diseases, such as eczema and rhinitis was more common in countries with higher acetaminophen sales.

• Acetaminophen sales and their association with atopic disease was investigated in 36 countries across the world.

• They found that English speaking countries (the United Kingdom, the Republic of Ireland, the United States, Canada, Australia, and New Zealand), which have some of the world's highest rates of allergic disease, also had some of the highest levels of acetaminophen sales.

• The prevalence of wheeze in adolescents increased, on average, by half a per cent for each gram increase in acetaminophen sales, per head of population.

Researchers hypothesize that the link may be due to the fact that acetaminophen reduces levels of the antioxidant glutathione in immune cells, thus impairing antioxidant defenses and promoting allergic inflammation.

Dr Shaheen said recent in vitro studies suggest that depletion of gluthatione can occur after clinically relevant doses of acetaminophen.

The earlier study in Thorax had found that daily acetaminophen users had a 138% increased incidence of asthma and weekly users had a 79% increase.

In an emailed response to the British Medical Journal's report of the recent study, Ron Law, Executive Director of the National Nutritional Foods Association of New Zealand (NNFA), criticized some of Dr. Shaheen's conclusions. He states:

I am intrigued by Dr Shaheen's reported comment that more evidence is needed to establish causality regarding the hypothesised link between paracetamol consumption and asthma; if it had been a dietary supplement the medical profession would have been baying for it to be removed from the market forth with -- it would be 'further evidence that dietary supplements are dangerous.'

European Respiratory Journal November, 2000; 16:1-7 and British Medical Journal November 11, 2000;321:1178A