It is disturbing that as we enter peak cough, cold and flu season, we are faced with the dilemma that acetaminophen (sold under the brand name Tylenol) may increase the risk of developing asthma.

The last major Tylenol scare occurred in the 80s when a few pill bottles were tainted with cyanide, intentionally, which killed seven people in the Chicago area. Of course, in that event, the problem with the popular pain killer had nothing to do with medication itself (investigators concluded the bottles had been tampered with after production and then replaced on the shelves).

Over the past several years, a growing number of studies have identified an association between acetaminophen intake and increased asthma and other allergic disorders. Last week, Reuters summarized the findings of a study published in the British medical journal Lancet, which linked paracetamol (the brand name of acetaminophen in Europe) to increased development of asthma and eczema in children.

The Lancet study included data from more than 30 countries and over 200,000, children. In short:

• Asthma risk was increased by 46% in children 6-7 years of age that had acetaminophen in their first year of life.

• Medium use of acetaminophen (defined as acetaminophen given one or more times per year but less than once monthly) in the previous 12 months resulted in a 60% increase in asthma.

• High dose use (doses given more than once per month) resulted in more than 3 times greater asthma risk.

Why is there an increased risk?
Acetaminophen, unlike, aspirin and ibuprofen, decreases the level of glutathione in the lungs and other places in our bodies. Glutathione is an antioxidant that reduces free radicals which may have a toxic effect on the lung and surrounding tissue. Other studies have reported similar findings and support this explanation.

Is there increased risk to the unborn child if acetaminophen is taken during pregnancy?
Last week I would have answered by saying I don't think anyone has reported a study on pregnant women and acetaminophen use. But there are two studies, the most recent one published in this month's Annals of Allergy Asthma and Immunology (AAAI) -- "Prenatal exposure to acetaminophen and respiratory symptoms in the first year of life" AAAI.2008; 101:271-278

In this study, 345 women were followed from the first trimester of pregnancy through the first year of their child's life. Researchers evaluated acetaminophen use by questionnaire and correlated with respiratory symptoms of the newborn during infancy.

In a nutshell: Acetaminophen taken in mid to late pregnancy (third or fourth trimester) was associated with increased wheezing or coughing in the newborn's first year of life.

There were some flaws in how this study was designed:

• The frequency and doses of acetaminophen taken in pregnancy were not reported.

• The reasons for taking acetaminophen (e.g. infection, other ailments) were not well documented. Such reporting may have allowed the identification of another cause for the increased respiratory symptoms in infancy (a certain virus or bacterial cause of wheezing in the infants).

• Finally, wheezing in the first year of life does not have a direct correlation with future asthma. I recently reviewed how early wheezing impacts the risk of developing asthma.

Why do these studies on Acetaminophen create a potential dilemma?
Acetaminophen became more preferable for children in the 1980s when Reyes syndrome was reported to be associated with aspirin use in children with certain febrile viral illnesses. Reyes syndrome was characterized by a host of medical problems that included severe brain and liver injury. In 1986, the Food and Drug Administration had warning labels about the risk of Reyes syndrome placed on all aspirin products.