Researchers recently discovered that cosmetic preservatives such as benzalkonium chloride and formaldehyde can be toxic to meibomian gland epithelial cells; exposure could lead to cellular atrophy and death—within hours. They noted that this is not unique and have since found that methylparaben, ethylparaben, phenoxyethanol and chlorphenesin also exert adverse effects on the meibomian gland cells.

The team cultured meibomian gland epithelial cells under proliferating and differentiating conditions with varying concentrations of methylparaben, ethylparaben, phenoxyethanol and chlorphenesin for up to five days. They then monitored the cells’ signaling ability, appearance, number, neutral lipid content and lysosome accumulation.

The investigators found that 30 minutes of exposure to these preservatives resulted in a significant reduction in cell activity, an effect they confirmed is dose-dependent and occurs at concentrations equal to (chlorphenesin) or less than (all others) dosages approved for human use.

Looking into longer-term effects, the study authors observed cellular atrophy and death after 24 hours of exposure. At all concentrations tested, they noted that none of the preservatives stimulated cell proliferation. They added that it was not possible to evaluate the influence of these preservatives at even close to human-approved dosages because the cells did not survive the treatment.