Dupixent Side Effects Your Doctor May Not Have Warned You About

If you’ve been prescribed Dupixent (dupilumab) for eczema, asthma, or another inflammatory condition, your doctor likely walked you through the common side effects — injection site reactions, eye irritation, cold sores, and joint pain. Those are all listed on the drug’s FDA-approved label.

What’s not on the label is the one side effect that matters most.

Multiple peer-reviewed studies have linked Dupixent to an increased risk of cutaneous T-cell lymphoma (CTCL), a rare and aggressive form of skin cancer. The FDA flagged Dupixent as a potential serious safety risk in March 2025 — yet as of 2026, the drug’s warning label still says nothing about cancer.

The Side Effects Dupixent’s Label Does Disclose

Dupixent’s prescribing information lists a range of known side effects that vary depending on the condition being treated. For eczema patients, the most commonly reported include:

• Injection site reactions (redness, swelling, itching)
• Eye and eyelid inflammation, including conjunctivitis, keratitis, and dry eye
• Cold sores on the mouth or lips
• Elevated eosinophil counts (a type of white blood cell)

For asthma and nasal polyp patients, additional reported side effects include throat pain and back pain.

The label also warns about rare but serious allergic reactions, blood vessel inflammation, and joint problems severe enough to require hospitalization in some cases. Patients are instructed to report new or worsening eye symptoms and to avoid live vaccines during treatment.

These are real risks, but most patients and their doctors are prepared for them. The problem is what the label leaves out.

The Side Effect That’s Missing: A Link to Skin Cancer

Dupixent works by blocking two proteins in the immune system — IL-4 and IL-13 — that drive the type of inflammation behind eczema, asthma, and related conditions. For many patients, this mechanism delivers genuine relief.

But those same immune pathways also play a role in the body’s ability to detect and destroy abnormal cells. By suppressing that signaling, Dupixent may impair immune surveillance in ways that allow a rare cancer — cutaneous T-cell lymphoma (CTCL) — to develop, progress, or go undetected.

The research on this is substantial and growing:

• A 2024 study in the Journal of the American Academy of Dermatology found that eczema patients on Dupixent were 4.1 times more likely to develop CTCL than those not on the drug
• An analysis published in Dermatologic Therapy found a relative risk of 4.59 for CTCL among Dupixent users, with 62% of cases diagnosed within the first year of treatment
• A 2025 study in the European Respiratory Journal found that asthma patients on Dupixent also faced a significantly elevated risk — over 4.5 times higher than patients on other therapies
• The FDA’s adverse event database shows CTCL was reported roughly 30 times more frequently for Dupixent than for all other drugs combined

Despite this body of evidence, Sanofi and Regeneron have not updated Dupixent’s warning label to include any mention of CTCL or cancer risk.

Why This Matters: CTCL Looks Like Eczema

This isn’t just a labeling technicality. It’s dangerous because CTCL, in its early stages, presents almost identically to eczema — red, scaly, itchy patches on the skin that come and go.

So here’s what may happen in practice: a patient is prescribed Dupixent for eczema. Their skin symptoms appear to improve. Both the patient and their doctor take that as a sign the drug is working. But in some cases, what’s actually happening is that Dupixent is suppressing the visible inflammation caused by an undiagnosed cancer — giving the appearance of improvement while the malignancy progresses underneath.

By the time CTCL is eventually identified — often only after a biopsy reveals what standard treatments can’t explain — the disease may have advanced significantly. Some patients have been diagnosed with mycosis fungoides or Sézary syndrome, two CTCL subtypes that can spread to the lymph nodes, blood, and internal organs.

Without a cancer warning on the label, neither patients nor prescribing physicians had any reason to consider CTCL as a possibility before starting Dupixent. That failure to warn is at the center of the lawsuits now being filed against Sanofi and Regeneron.

What to Watch For If You’ve Taken Dupixent

If you are currently taking or have previously taken Dupixent, pay attention to skin changes that don’t behave like your typical eczema flares. Symptoms that warrant a conversation with your doctor include:

• Patches, plaques, or rashes that persist despite treatment or look different than usual
• Skin thickening or discoloration that spreads or worsens over time
• Itching that doesn’t respond to standard eczema treatments
• Swollen lymph nodes in the neck, armpits, or groin
• Unexplained weight loss, fatigue, fever, or night sweats

These symptoms don’t automatically mean cancer, but they should be evaluated — especially if you’ve been on Dupixent. Ask your doctor about whether a biopsy is warranted. Do not stop taking Dupixent without consulting your physician first.

Your Legal Options If You Were Diagnosed with CTCL After Dupixent

Patients who took Dupixent and were later diagnosed with CTCL, mycosis fungoides, Sézary syndrome, or another form of T-cell lymphoma may have a legal claim against the drug’s manufacturers.

The Higgins Firm is actively investigating Dupixent claims on behalf of patients in Tennessee and across the country. The first wrongful death lawsuit in this litigation was filed right here in Tennessee in October 2025.

The consultation is free and confidential. You pay nothing unless we recover compensation for you. If you have questions about your Dupixent use and a subsequent cancer diagnosis, contact The Higgins Firm today.