Does nail polish impact pulse oximeter accuracy?

Nail polish or nail varnish can impact pulse oximeter accuracy, so it is best to remove the polish to allow the light from the probe to pass through the tissue. If it cannot be removed, placing the probe on the toe or on the fingertip sideways can be an option.  

Certain colors of nail polish may lead to underestimation of SaO2 by pulse oximetry. Studies have shown that in healthy adults, blue, green, black, purple and brown nail polish appear to interfere the most with pulse oximeter SpO2 readings. In fact, they can cause readings of up to a 3-5% underestimation in oxygen saturation, though data are mixed. 

Another study, which examined different nail polish colors on 50 critically ill patients, showed that all colors interfered with pulse oximetry readings, but that the most significant interference was due to black, purple, and dark blue polish. All other nail polish colors had a lesser effect on pulse oximeter readings. 

Regarding gel nail polish, a study in 17 healthy adults tested several colors of gel-based manicure, and concluded that certain colors of gel polish resulted in a significant overestimation of SpO2, although their results varied when using different brands of pulse oximeter.

A recent review on the topic was published in 2023 and concluded only marginal reductions on SpO2.

References: Lifebox Pulse Oximetry Learning Module, Ralston et al, Anaesthesia 1991; Adler et al, Acad Emerg Med 1998; Hinkelbein et al, Resuscitation 2007; Yönt et al, Intensive Crit Care Nurs 2014; Coté et al, Anesth Analg 1988; Yek et al, Singapore Med J 2019 Aggarawal et al, Respiratory Care, 2023.

Keywords: nail polish, varnish, nail color