Salicylic acid, a popular topical acne treatment and active component in willow bark extract and Aspirin, may lead to upper respiratory tract infections according to researchers at the Institute of Microbiology, Vetmeduni Vienna, and the University of Buenos Aires.
Staphylococcus aureus (S. aureus ) can colonize the upper respiratory tract of around one quarter of the human population but usually isn’t harmful. If the host is healthy and the bacteria obtain sufficient nutrients, the bacteria remain “quiet” and are kept under control by the immune system. They may, however, become active in response to infections by another pathogen or illness weakening the host immune system.
The regular consumption of salicylic acid, or its consumption in higher doses, could unexpectedly promote and prolong bacterial colonization, according to the researchers.
The metabolism of many bacteria, including S. aureus, depends on the availability of iron molecules. Salicylic acid forms complexes with iron ions in the blood and so deprives the staphylococcal bacteria. S. aureus modifies its metabolism if it’s not getting enough iron and forms a biofilm.
Researchers say the increased consumption of salicylic acid promotes this biofilm formation, which then can lead to infections of the upper respiratory tract.
As pain relief medication, this compound is usually not taken regularly. However, it also is a component of anti-acne preparations and certain exfoliate products, which are often used for a longer period of time. Researchers did not clarify whether topical use of salicylic acid poses the same risk as ingestion.