What Happens If You Don’t Remove Nail Polish Before Surgery?

Leaving nail polish on before surgery usually will not cause a medical emergency, but it can complicate the monitoring equipment your surgical team depends on. The main concern is the pulse oximeter, a small clip placed on your fingertip that uses light to measure your blood oxygen levels throughout the procedure. Darker polishes can interfere with that light, and newer research suggests the interference is smaller than once believed, though it still matters in certain situations. There is also a separate concern about visual assessment of your nail beds and, surprisingly, little evidence that polish has anything to do with infection risk.

Why the Surgical Team Cares About Your Fingernails

During any operation under general anesthesia, the anesthesia team continuously tracks how well oxygen is reaching your tissues. The workhorse device for this job is the pulse oximeter. It clips onto a fingertip and shines two wavelengths of light, one red and one infrared, through your finger. Oxygenated blood absorbs these wavelengths differently from deoxygenated blood, so by comparing how much of each wavelength makes it through, the device calculates your oxygen saturation (the familiar “SpO2” number on the monitor).¹ Anything sitting between the light source and your finger’s blood vessels, including layers of colored lacquer, can absorb or scatter that light and throw off the reading.

Beyond pulse oximetry, clinicians sometimes glance at your nail beds during and after surgery. The color of the tissue under your nails gives a quick, low-tech sense of circulation. Pale or blue-tinged nail beds can signal poor blood flow or low oxygen. If your nails are covered in opaque polish, that visual cue disappears. In procedures involving the hands or arms, surgeons may also need to see the nail beds to assess blood supply to the extremity.

How Much Does Nail Polish Actually Affect Oxygen Readings?

The short version: dark colors cause measurable but usually small drops in the SpO2 number. A systematic review that pooled results across multiple studies found that black, blue, brown, and purple nail polish all produced statistically significant reductions in pulse oximeter readings, but the actual size of those reductions was small enough that the review’s authors described them as “clinically insignificant” for most patients.² In plain terms, the readings dipped by fractions of a percentage point on average, not enough to change a treatment decision in someone whose oxygen levels are otherwise normal.

The bigger practical problem showed up in one of the studies included in that review: when fingers were painted with black polish, the oximeter failed to produce a reading entirely about 88% of the time. Brown polish caused failures about 36% of the time.² A slightly inaccurate reading is one thing; getting no reading at all during surgery is a genuinely serious problem. If the device cannot lock onto the signal, the anesthesia team loses one of its most important real-time safety monitors.

That said, the degree of interference varies with the brand of oximeter as well as the polish color. A study testing gel-based manicures found that with one brand of oximeter, light blue and orange gel polish actually nudged SpO2 readings slightly upward rather than downward, while a different brand of oximeter showed wide imprecision, especially with black gel polish, where the range of potential error stretched to around 17%.³ The takeaway is that the size and direction of the error are unpredictable. What matters clinically is not the average shift across a study but whether a particular color on a particular machine might mask a dangerous drop in oxygen in a specific patient, especially someone whose oxygen levels are already borderline.

The Problem That Is Not About Oxygen at All

Most of the concern about nail polish and pulse oximeters focuses on the oxygen saturation number. But the same device also reports your pulse rate, and here nail polish can cause a stranger kind of trouble. A published case report described a patient wearing white nail polish whose oxygen readings looked perfectly normal yet whose pulse rate display jumped wildly between very slow and very fast values. The clinical team, understandably worried about a possible heart rhythm problem, ordered a full electrocardiogram, which turned out to be completely normal.⁴

White polish is worth noting because it is not a “dark” color, and most patients would assume it is harmless. The issue is that certain pigments distort the shape of the light waveform even when they do not block enough light to change the oxygen number. The oximeter then misinterprets the waveform’s peaks and troughs, producing a phantom heart rhythm that does not actually exist. In a high-stakes environment like an operating room, this kind of false alarm can lead to unnecessary tests, delayed procedures, or misguided treatment decisions.

What About Acrylic or Gel Nails?

Acrylic overlays without any polish on top are a different story. A study that measured oximetry readings before and after applying unpolished acrylic nails found no significant difference, with mean readings of about 97.3% at baseline and 97.6% after application.⁵ The acrylic material itself is largely transparent to the wavelengths used by the oximeter. What causes trouble is the pigment in the polish layered on top, not the structural overlay underneath.

Gel manicures sit somewhere in between. The gel base coat alone is relatively transparent, but the color coats are essentially polish baked into a hard shell, making them harder to remove on the spot than regular lacquer. If your surgical team asks you to clear at least one fingertip, a gel or dip-powder manicure can be a real headache because it requires filing or soaking with acetone, neither of which is practical in a preoperative holding area. Some patients end up having the oximeter placed on a toe or earlobe instead, which introduces its own accuracy trade-offs.

Where Else Can They Put the Oximeter?

When fingers are unavailable, the earlobe is generally the next best option. In a study of intensive care patients after heart surgery, earlobe probes showed the strongest agreement with the gold standard (an arterial blood draw), outperforming toe and forehead placements.⁶ Separate research in children found a similar pattern, with ear probes offering the highest clinical agreement and toe probes the lowest, particularly in newborns.⁷

Forehead sensors also exist and are used in certain settings, though they tend to be less precise than finger or earlobe probes. In practice, if you show up to your surgery with a full set of dark gel nails, the team will not cancel your operation. They will move the probe to an alternative site or, if time allows, remove the polish from one or two fingers. The point is that workarounds exist, but they are less ideal, and starting with a clean fingertip available is the simplest path to the best monitoring.

Does Nail Polish Raise Infection Risk?

This is where the gap between hospital policy and actual evidence is widest. Many preoperative instruction sheets tell patients to remove all nail polish, and some specifically cite infection concerns. The reality is that no randomized trial has ever tested whether wearing nail polish affects surgical wound infection rates. A Cochrane systematic review, the gold standard for evaluating medical evidence, looked for exactly this data and came up empty.⁸

The only trial the review found involved 102 scrub nurses whose hands were tested for bacteria after surgical scrubbing. One group had unpolished nails, one had freshly applied polish (less than two days old), and one had old polish (more than four days old). There were no significant differences in bacterial counts between any of the groups.⁸ This was a small trial looking at scrub nurses rather than surgical patients, and it measured bacteria on hands rather than actual wound infections, so it is far from definitive. But the absence of any stronger evidence is striking given how universally the “remove your polish” instruction is given.

In practice, the infection-control rationale probably applies more to the surgical team (whose hands enter the sterile field) than to you as a patient (whose painted fingernails are usually nowhere near the surgical site). Hospital policies tend to be conservative, bundling anything with a theoretical risk into a single instruction sheet rather than nuancing each item. That is not unreasonable from a safety standpoint, but it does mean the infection justification for removing your polish is tradition-based rather than evidence-based.

What You Should Actually Do Before Surgery

Most hospitals will ask you to arrive with at least one or two bare fingernails, typically on different hands. If you have regular polish, that is a quick wipe with acetone. If you have gel, dip, or acrylic nails, plan ahead: either remove them a few days before or ask your salon to leave one or two nails bare. Some facilities will specify which fingers they prefer bare (often the index finger of your non-dominant hand), so check your preoperative instructions.

If you forget or cannot remove your polish in time, be honest with the preoperative nurse. They deal with this constantly and have acetone remover on hand for standard lacquer. For gel or acrylics, they will likely move the oximeter to a toe or earlobe and note it in your chart. The surgery will proceed. You will not be turned away at the door. However, your anesthesia team will have one less optimal monitoring site, and in a true emergency where seconds matter, every bit of monitoring reliability counts.

Toenails deserve a quick mention. If you are having lower-extremity surgery, or if the team anticipates needing a toe probe, you may be asked to remove toenail polish as well. For most surgeries, though, the focus is on fingernails because finger probes are the clinical default and give the most reliable readings.

When the Stakes Are Higher

For a healthy person having a routine procedure, the risk of nail polish causing a genuine clinical problem is low. The oximeter might read a point or two off, which barely matters when your baseline oxygen level is normal. The calculus changes for patients who already have compromised oxygen levels, such as those with lung disease, severe heart conditions, or conditions affecting blood flow to the extremities. In these patients, a small downward error in the SpO2 reading could push the displayed number below a treatment threshold, prompting unnecessary intervention, or, more dangerously, the polish-induced error could mask a real drop in oxygen by making a marginal reading appear acceptable.

The same concern applies to very long procedures. Over a six- or eight-hour surgery, even a slight bias in the oximeter’s reading can become relevant if it drifts the displayed number consistently in one direction. Anesthesiologists calibrate their decision-making around the trend of that number over time, not just a single snapshot. A persistent one-percent error introduced by dark polish might not matter in isolation but could matter in context, especially combined with other sources of signal noise such as poor circulation, hypothermia, or movement.

Nail Color and Skin Tone

An area of growing awareness in medicine is that pulse oximeters themselves are less accurate on people with darker skin tones, even without any nail polish in the picture. The devices were historically calibrated using study populations that were predominantly light-skinned, and research over the past several years has shown that oximeters can overestimate oxygen levels in people with more melanin. When you layer the potential error from dark nail polish on top of the potential error from skin pigmentation, the margin for inaccuracy widens further. This is not a reason for panic, but it is another reason clinicians prefer to start with the cleanest possible signal from a bare fingertip.

The issue also helps explain why some hospitals have shifted their policies from “remove all nail polish” to “ensure at least one or two bare fingers.” A blanket ban made sense when the concern was binary, polish versus no polish. A more nuanced policy recognizes that the biggest risks come from specific dark colors combined with other patient-specific factors, and that light or sheer polishes on most of your nails are unlikely to matter as long as the team has one clean finger for the probe.

Why Hospitals Have Not Updated Their Policies Faster

Given the modest evidence for most of the concerns, you might wonder why the “remove all nail polish” instruction persists so universally. Part of the answer is institutional inertia: preoperative checklists are reviewed infrequently, and changing any item requires committee approval, documentation updates, and staff retraining. Part of it is the precautionary principle applied broadly. In an environment where a preventable complication can mean a malpractice claim, the cost of asking patients to remove their polish is essentially zero, while the cost of a monitoring failure during surgery is enormous. Even if the actual risk is small, the asymmetry between the effort of prevention and the severity of the potential problem keeps the policy in place.

There is also a communication issue. The instruction “remove all nail polish” is simple and unambiguous. An instruction like “remove dark-colored polish from at least two fingernails, but sheer pink on the rest is probably fine” introduces judgment calls that patients might get wrong and that preoperative nurses would have to adjudicate case by case. Healthcare systems tend to favor bright-line rules over nuanced ones, especially for instructions given to large numbers of patients with varying levels of health literacy. The result is a policy that is broader than the evidence strictly demands but is easy to follow and eliminates guesswork on both sides.