Dr. Joseph Mercola reports that high consumption of acetaminophen, the active ingredient in Tylenol, may increase the risk of developing asthma. Dr. Seif Shaheen from King’s College in London has published research which links high rates of allergic disease with high levels of acetaminophen sales in different countries. English-speaking countries lead in both acetaminophen sales and allergic disease. Dr. Shaheen’s research team also found a correlation between the prevalence of wheeze in adolescents and the level of acetaminophen sales. An earlier study found that daily acetaminophen users had a 138% increased incidence of asthma; weekly users had a 79% increase.

Researchers hypothesize that acetaminophen may deplete glutathione, an important antioxidant in the immune system. Dr. Mercola cautions that it is unwise to use Tylenol to control fever in children — because a fever is a natural response to infection, and controlling a fever with Tylenol may prevent proper development of the immune system and increase the chance of allergic disease.