Relador Side Effects: What to Expect and When to Call Your Doctor

Relador (lidocaine 2.5%/prilocaine 2.5% topical cream) is generally considered safe when used exactly as prescribed. Most people who use it experience only mild, temporary local reactions at the application site. However, serious adverse effects are possible — particularly methemoglobinemia — and it's important to know the difference between what's expected and what requires immediate medical attention.

Common, Expected Side Effects at the Application Site

These effects are expected and typically resolve on their own within 1–2 hours of removing the cream:

Pallor (blanching): The skin may turn white or pale where the cream was applied. This is caused by vasoconstriction (narrowing of blood vessels) and is completely normal.

Erythema (redness): Some patients experience redness or flushing at the application site after the cream is removed, as blood vessels dilate. This is normal and temporary.

Edema (swelling): Mild puffiness or swelling at the application site may occur.

Itching or burning sensation: A tingling, itching, or mild burning feeling while the cream is working is common and not a cause for concern.

Temperature changes: The skin may feel unusually warm or cool after removal. This is a normal side effect.

These local reactions require no treatment and are not a reason to stop using the medication if prescribed.

Serious Side Effect: Methemoglobinemia

The most serious potential side effect of Relador is methemoglobinemia — a condition where hemoglobin in the blood is converted to a form (methemoglobin) that cannot carry oxygen effectively. Both lidocaine and prilocaine can cause this, with prilocaine carrying the higher risk.

Methemoglobinemia is rare with correct use, but the risk increases with:

Application to large areas of skin or mucous membranes

Application under occlusion for longer than recommended

Use in patients with G6PD deficiency, congenital methemoglobinemia, or cardiac/pulmonary conditions

Use in infants under 12 months receiving other methemoglobin-inducing drugs, or under 3 months old

Concurrent use of drugs that increase methemoglobin levels (dapsone, sulfasalazine, nitrofurantoin, phenobarbital, phenytoin, nitroglycerin, chloroquine)

Warning Signs of Methemoglobinemia — Call 911 Immediately

Seek emergency medical care immediately if you or someone you know shows any of these symptoms after applying Relador:

Cyanosis: Blue or gray discoloration of the lips, fingernails, or skin

Difficulty breathing or shortness of breath

Dizziness, lightheadedness, or fainting

Rapid or irregular heartbeat

Confusion or altered mental status

Seizures

Allergic Reactions: Signs to Watch For

People who are allergic to amide-type local anesthetics (lidocaine or prilocaine) should not use Relador. Signs of an allergic reaction include:

Widespread rash or hives beyond the application site

Swelling of the face, lips, tongue, or throat (angioedema)

Difficulty swallowing or breathing

Sudden drop in blood pressure or feeling faint

If you experience any of these symptoms, remove the cream immediately, call 911, and seek emergency care.

Safe Use Guidelines to Minimize Risk

Apply only the amount prescribed — do not use more than directed

Do not apply to broken skin, open wounds, or areas near the eyes

Do not leave on longer than prescribed — remove promptly before the procedure

Tell your doctor all medications you are currently taking — especially those on the interaction list

Keep out of reach of children — accidental ingestion is dangerous

For a complete list of drug interactions with Relador, see our guide to Relador drug interactions. And to learn more about how Relador works, see what Relador is and how it's used.