Applying nail polish can lead to the display of inaccurate oxygen saturation (SpO2) readings on pulse oximeters, a recent study conducted by the department of pulmonary medicine at the Post Graduate Institute of Medical Education and Research (PGIMER) has uncovered.

According to a systematic review led by a team of doctors, including Dr Ashutosh N Aggarwal, Dr Ritesh Aggarwal, Dr Sahajal Dhooria, Dr Kuruswamy T Prasad, Dr Inderpaul S Sehgal and Dr Vallappan Muthu, wearing nail polish, especially in darker shades, can interfere with oximeter readings. The study, conducted without any external funding, was presented during the researchday celebrations at the institute in March.

The PGIMER team reviewed 117 studies published up to May 2022 across medical databases like PubMed, EMBASE, and CINAHL, narrowing down its analysis to 21 suitable studies. These studies examined the effects of various nail polish colours, including black, blue, red, and yellow on SpO2 readings.

A pulse oximeter is a small, non-invasive device that measures blood oxygen saturation level (SpO2) and heart rate. The team concluded that while not all nail polishes affect oximeter readings equally, dark-coloured nail polish, particularly black, poses a notable concern as it can show artificially lower SpO2 levels. This could potentially lead to misjudgment in critical cases, where an accurate assessment of a patient's oxygen levels is crucial.

How to ensure accurate measurement

As per PGIMER study, black nail polish was found to reduce oxygen saturation readings by an average of 0.57 points, an impact deemed statistically significant. Lighter or less intense shades, such as yellow, brown and green, had minimal to negligible effects on the readings.

The researchers advise healthcare professionals and patients not to rely solely on pulse oximeter readings if anyone is wearing dark nail polish. They recommend either removing the polish or taking the measurement from an unpainted finger. The finding has important implications for at-home health monitoring, especially when pulse oximeters have become a household essential since the Covid-19 pandemic.

Doctors emphasise that even seemingly minor factors like nail polish should be taken seriously when assessing SpO2 levels.