What Is Lidocaine and Prilocaine Cream Used For?

Lidocaine and prilocaine cream is a topical anesthetic that numbs the skin before needle sticks, minor procedures, and certain other painful treatments. Sold under the brand name EMLA (Eutectic Mixture of Local Anesthetics) and various generics, it combines two local anesthetics at 2.5% each into an oil-in-water emulsion that can penetrate intact skin without an injection. The cream has been in clinical use since the 1980s and remains one of the most widely studied topical anesthetics in both adults and children, though it has quirks and limitations that are worth understanding before you squeeze it out of the tube.

Why Two Drugs Instead of One

Lidocaine and prilocaine individually are crystalline solids at room temperature. Neither dissolves well enough on its own in a simple cream base to penetrate the skin’s outer barrier in useful concentrations. When the two are mixed in roughly equal proportions, they form what chemists call a eutectic mixture, meaning they lower each other’s melting point enough to become liquid at room temperature. That liquid mixture can then be dispersed as tiny oil droplets in water.

This formulation matters for a practical reason. Because the anesthetic bases are already in their uncharged, fat-soluble form, they move across the skin’s lipid-rich outer layer more efficiently than a conventional cream loaded with a water-soluble salt of a single anesthetic. The water phase acts as a poor solvent, which keeps the system saturated and drives the drugs outward into the skin. And the droplets of liquid drug serve as reservoirs, steadily replenishing what diffuses away. The net result is deeper, more reliable numbness than you would get from a comparable concentration of lidocaine alone in a standard base.

How Deep It Numbs and How Long You Wait

The cream needs time under an occlusive dressing, typically a piece of plastic wrap or a supplied adhesive patch, to work. One classic study measured pain thresholds at various depths after different application times and found that maximum analgesia, reaching about 5 mm deep, occurred roughly 30 minutes after removing the cream following a 90-minute application.¹ For shorter applications, the numbness actually continued to deepen after the cream was wiped off, because the drug stored in the outer skin layers kept diffusing inward.

A more recent trial comparing EMLA to a 10% lidocaine cream put finer numbers on the relationship between wait time and depth. With a 60-minute application, EMLA provided acceptable pain control to a needle-insertion depth of about 6.6 mm; with 120 minutes, that increased to roughly 9.5 mm.² In practical terms, 60 minutes is the standard recommendation for most needle procedures, though many clinicians settle for 30 to 45 minutes when time is tight and the procedure is shallow, such as a blood draw.

What Happens to the Skin Underneath

If you have ever peeled off an EMLA dressing and noticed the skin looks pale or whitish, that is not an allergic reaction. The cream causes initial vasoconstriction, a narrowing of tiny blood vessels near the surface, that peaks around 90 minutes after application.³ Part of the blanching also comes from the occlusive dressing hydrating the outer skin layer, which changes how light reflects off it.⁴

After the dressing comes off and the stratum corneum starts to dry, the blanching fades and is often followed by redness. The redness happens because the initial vasoconstriction reverses into vasodilation, likely from the direct muscle-relaxing effect of the anesthetics on blood vessel walls. If the cream is left on for more than about three hours, vasodilation dominates.⁵ Both phases are temporary and cosmetically harmless, but there is a clinical wrinkle: the vasoconstriction can make veins harder to find. If you are applying the cream before an IV insertion, the timing matters. Waiting too long (or not long enough) can actually make the nurse’s job trickier.

There is also a measurable change in skin thickness. An ultrasound study found that EMLA under occlusion increased mean skin thickness from about 1.86 mm to 1.96 mm, and the swelling correlated with how long the cream was left on.⁶ For a routine blood draw, that is irrelevant. For surgeons harvesting split-thickness skin grafts, which depend on precise depth control, it is something to account for.

Children and Needle Pain

Pediatric needle procedures are where EMLA arguably has its longest track record and most emotional impact. Studies going back decades confirm the cream reduces pain during intravenous cannulation and blood draws in children compared to placebo.⁷ A recent randomized trial in children aged 7 to 12 compared EMLA to cold spray, a vibrating device (Buzzy), and no intervention. All three methods lowered pain compared to doing nothing, but EMLA produced the lowest pain scores and also reduced needle-related fear.⁸

In preterm infants, the picture is somewhat less dramatic. A study of premature neonates found that combining EMLA with oral sucrose reduced pain scores during venipuncture compared to sucrose alone, but the pain was not eliminated, just blunted.⁹ Premature infants have thinner skin and different pain-processing systems, so the cream works somewhat differently in this group. Dosing must be conservative because of the methemoglobinemia risk discussed below.

Research on infants has also confirmed that lidocaine and prilocaine are absorbed into the blood in low concentrations and that methemoglobin levels do not rise after standard EMLA doses during vaccination or circumcision.¹⁰ Fear reduction is an underappreciated benefit in older children. When kids learn that needles do not have to hurt, they tend to be less anxious about future medical visits, a phenomenon confirmed in a study comparing EMLA to a needleless lidocaine delivery system, where both groups showed significantly lower post-procedure fear scores than before treatment.¹¹

Wound Care and Leg Ulcers

Cleaning out chronic leg ulcers by scraping away dead tissue, known as sharp debridement, is genuinely painful. Multiple controlled trials have shown that applying EMLA to the ulcer bed for 30 to 45 minutes under occlusion cuts the pain roughly in half and reduces the number of debridement sessions needed to get a clean wound.¹² A review of the clinical evidence across multiple trials confirmed that EMLA also reduces post-debridement pain and may save healthcare costs by speeding up the wound-healing timeline.¹³

A reasonable concern with repeated use on open wounds is systemic absorption. But studies tracking plasma drug levels have found low concentrations of lidocaine and prilocaine even with repeated applications, with no apparent accumulation over a course of treatments.¹⁴ Similarly, in adults with burns, peak plasma concentrations of both drugs combined remained far below toxic thresholds after applying 5 grams of EMLA to a 25-square-centimeter area for 30 minutes.¹⁵

Dermatology Procedures and Laser Treatments

EMLA is widely used before cosmetic laser treatments, microneedling, and other skin-resurfacing procedures. In a study evaluating topical anesthetics for superficial laser procedures and microneedling, the cream produced mean pain scores of about 4.4 on a 10-point scale, confirming useful but not complete analgesia for procedures that cover a broad skin area.¹⁶ For a patient getting a small area treated, a pain score of 4 out of 10 might feel perfectly manageable. For someone having their entire face microneedled, it might not be enough on its own.

For laser hair removal specifically, a randomized trial comparing EMLA to ice packs on the armpit found no significant difference between the two methods in terms of overall pain reduction.¹⁷ That is worth knowing if you are debating whether to spend 60 minutes under plastic wrap or simply hold an ice pack to the area for a few minutes beforehand.

How It Stacks Up Against Alternatives

EMLA is not the only topical anesthetic on the market, and it is not always the best one for a given situation. A systematic review of randomized trials found that tetracaine-based topical formulations, including liposome-encapsulated versions, tended to produce slightly better analgesia than EMLA for skin procedures, with the difference averaging about 8 to 11 mm on a 100-mm pain scale.¹⁸ That is a modest gap, but it can matter for sensitive patients or painful procedures.

EMLA’s biggest practical disadvantage compared to some newer products is its onset time. A heated lidocaine-tetracaine patch achieved significantly lower pain scores than EMLA at every time point under 60 minutes of application. At the 10-minute mark, median pain scores were roughly twice as high with EMLA. Only at the 60-minute mark did the two become equivalent.¹⁹ In an emergency department or a fast-paced clinic, the hour-long wait for EMLA can be a real barrier, and faster-onset alternatives may make more sense even if EMLA is ultimately just as effective.

Premature Ejaculation

One of the more widely discussed off-label uses of lidocaine-prilocaine cream is for managing premature ejaculation. The logic is straightforward: reducing penile sensitivity should delay climax. A systematic review and meta-analysis of topical anesthetics for premature ejaculation found that EMLA was significantly more effective than placebo at prolonging intravaginal ejaculatory latency time.²⁰ A separate randomized trial compared EMLA cream head-to-head with lidocaine spray and benzocaine condoms. All three extended time to ejaculation, with lidocaine spray producing the largest increase, EMLA coming in second, and benzocaine condoms third. Side effects were minimal across the board.²¹

The practical challenge is that the cream must be applied 20 to 30 minutes before intercourse and then wiped off or covered with a condom to avoid numbing the partner. This makes it less convenient than a spray, which dries faster. Dedicated products formulated specifically for this purpose exist and are often preferred in clinical practice, but generic EMLA remains a cheaper alternative.

The Methemoglobinemia Question

Methemoglobinemia, a condition where a modified form of hemoglobin cannot carry oxygen efficiently, is the most clinically serious side effect linked to this cream. Prilocaine is the primary culprit. When the body breaks down prilocaine, one of the metabolites, o-toluidine, oxidizes hemoglobin.²² Lidocaine can contribute through a different metabolite, 2,6-xylidine, but it does so less efficiently.

In practice, methemoglobinemia from standard EMLA doses on intact skin is rare. The risk rises when the cream is used on large areas, on broken skin, in neonates (who have lower levels of the enzyme that corrects methemoglobin), or alongside other drugs that can cause the same problem, such as certain sulfonamide antibiotics or dapsone. The prescribing labels for EMLA spell out maximum doses and application areas by age group. For most adults getting a small area numbed, the risk is effectively negligible.

Other Side Effects

The most common reactions are local and temporary: skin blanching, redness, mild swelling, and occasionally itching or a sensation of warmth at the application site. Less commonly, contact dermatitis (either allergic or irritant), localized hives, darkening of the skin, and purpura have been reported.²³ Purpura, which looks like small bruises, appears to be idiosyncratic and is rare enough to warrant case reports when it occurs. True allergic reactions to amide-type local anesthetics are uncommon, but they do exist. If you have had a confirmed allergy to lidocaine or prilocaine from dental work or another setting, the cream would be off-limits.

Veterinary Uses

EMLA has found a second life in veterinary medicine, particularly in cats. Cats are notoriously difficult to handle during blood draws and IV catheter placements, and studies have shown the cream makes a measurable difference. In one trial, every cat that received EMLA cream before IV catheter placement showed no reaction at all, while control cats frequently flinched or struggled.²⁴ A separate study on jugular blood draws found that withdrawal movements occurred in only one out of nine cats treated with EMLA, compared to seven out of nine in the placebo group, and the veterinary staff rated the procedure as easy in most EMLA-treated cats.²⁵ The researchers endorsed routine use of the cream as good practice for cat welfare.

The cream has also been studied in horses. A comparison between EMLA and injected lidocaine for a minor surgical procedure on mares found equivalent anesthesia, with the added benefit that the cream avoided tissue swelling from the injection that could distort the surgical site.²⁶ Pet owners who have watched their animal panic at the vet may want to ask about applying the cream before the visit, though the 30- to 60-minute wait still applies and the application site needs to be kept covered so the animal does not lick it off.

Application Tips That Actually Matter

A thick layer works better than a thin smear. The cream needs to sit in excess on the skin surface so the eutectic reservoir can keep feeding drug into the outer layers. Apply at least one to two grams per treatment site for a blood draw, and cover it with an occlusive dressing. Plastic kitchen wrap works as well as any medical product for this purpose.

Timing is not just about waiting long enough. If you apply EMLA and then leave it for three or four hours because you got distracted, the vasodilation phase will be well underway, potentially making the area red and puffy without additional benefit. For most needle procedures, 60 minutes is the sweet spot between numbness and manageable skin changes. Hair at the application site does not need to be shaved, but it can make peeling off adhesive dressings more uncomfortable, somewhat defeating the purpose.

After the dressing comes off, the residual drug stored in the outer skin continues to work for a while. Studies show that the numbness can persist for 30 to 60 minutes after removal, depending on how long the cream was applied. If you are numb enough when the dressing comes off, do not wait for the numbness to “peak” further; the procedure can start right away.

Who Should Be Cautious

Beyond the methemoglobinemia concern already described, a few groups deserve extra care. People with glucose-6-phosphate dehydrogenase (G6PD) deficiency are at higher risk for methemoglobinemia from oxidant stress and should discuss alternatives with their provider. Neonates younger than three months, especially preterm infants, have immature enzyme systems and should receive lower maximum doses than older children. Anyone taking a class III antiarrhythmic drug should avoid the cream because of potential additive cardiac effects from absorbed lidocaine. And patients with significant liver disease may metabolize both drugs more slowly, increasing the risk of systemic accumulation if the cream is used on large areas or broken skin.

For most healthy adults applying the cream to a few square centimeters of intact skin, these cautions are academic. The cream has decades of use behind it, and serious systemic events from routine application are vanishingly rare. The biggest real-world problem is not toxicity but impatience: people do not want to wait an hour, so they skip the cream entirely or wipe it off too early and conclude it does not work.