Acneiform Rashes

An acneiform rash—also called papulopustular exanthema—is a common skin reaction that looks like acne but is caused by cancer treatments, not clogged pores. It usually appears on the face, scalp, chest, and upper back as red bumps (papules) and pus-filled spots (pustules). You may also feel itching, stinging, or pain in the affected areas.

This rash is most common with targeted therapies that block a protein called EGFR (epidermal growth factor receptor), which helps keep skin healthy. These treatments include:

• Tyrosine kinase inhibitors (TKIs): erlotinib, afatinib, dacomitinib, osimertinib, lapatinib, gefitinib
• Monoclonal antibodies: cetuximab, necitumumab, pertuzumab, panitumumab
• MEK inhibitors (used for melanoma): trametinib, binimetinib, cobimetinib

Up to 90% of patients may develop this rash, usually within the first few days or weeks of starting treatment. In some cases, the rash can become severe and even infected, especially by bacteria. Interestingly, having a rash may be a sign that the treatment is working well.

Why Do Targeted Therapies Cause This Rash?

Acne-like rash is a common side effect of certain cancer treatments that target specific skin pathways, such as EGFR or MEK. These treatments can disrupt normal skin function, causing inflammation and weakening the skin’s natural defenses. This makes it easier for bacteria to grow, leading to infection.

The rash usually appears on areas with more oil glands, like the face, scalp, chest, and upper back, because these spots are more sensitive and prone to inflammation.

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How to Grade the Severity of Acneiform Rashes?

What Can I Do to Prevent Acneiform Rashes?

Preventing acneiform rashes starts before treatment begins. These steps can help reduce your risk and keep your skin comfortable during therapy:

1. Prepare your skin before treatment
   • Your doctor will examine your skin before starting treatment and may treat any existing conditions to strengthen your skin barrier.
2. Follow daily skin care and lifestyle practices
   • Avoid frequent washing with hot water, including showers, baths and handwashing
   • Use gentle, alcohol-free moisturizers twice dailyProducts containing 5% to 10% urea are especially helpful for maintaining hydration and skin barrier function.
   • Avoid over-the-counter acne products, disinfectants, and harsh solvents that may irritate your skin
   • Minimize sun exposure and apply sunscreen with SPF 15 or higher every two hours when outdoors to protect against sun-triggered irritation.

Start preventive medications if prescribed

• Take oral antibiotics for six weeks from the start of therapy (e.g. doxycycline 100 mg twice daily, minocycline 100 mg once daily, or oxytetracycline 500 mg twice daily)
• If allergic or intolerant, alternatives may include cephadroxil or trimethoprim-sulfamethoxazole
• Your doctor may recommend a low to moderate strength steroid cream for the face and chest once to twice daily to reduce inflammation.

If your rash is mild to moderate (Grade 1–2):

1. Your doctor will usually continue your cancer treatment as planned.
2. You may be given oral antibiotics like doxycycline, minocycline, or oxytetracycline for about six weeks to help calm the inflammation.
3. A gentle steroid cream may be prescribed to reduce redness, swelling, and discomfort.
4. Keep following the preventive skin care steps—moisturize regularly, avoid hot water and harsh products, and protect your skin from the sun.
5. Your doctor or nurse will check your skin after two weeks. If the rash gets worse or doesn’t improve, your treatment may be adjusted.

If your rash is severe (Grade 3 or a very uncomfortable Grade 2):

1. Your doctor may temporarily pause your targeted therapy until the rash settles down.
2. Oral antibiotics will be prescribed for about six weeks to reduce inflammation.
3. A steroid cream will be recommended to soothe the skin.
4. You may also be given a short course of oral steroids, such as prednisone, for about seven days to help control the rash.
5. If your rash looks infected, such as having yellow crusts, pus, or painful spreading areas, your doctor may take a skin swab and prescribe antibiotics based on the results.
6. If other treatments don’t work, your doctor may consider low-dose isotretinoin. This is only used in special cases.
7. Your healthcare team will keep a close eye on your progress and adjust your treatment to make sure you stay comfortable and safe.
8. If the rash is very severe or difficult to manage, your doctor may advise hospital admission to consult a dermatologist for specialized care.

▶️ 抗 EGFR 治療常見皮膚副作用及其處理方法（一）

▶️ 抗 EGFR 治療常見皮膚副作用及其處理方法（二）