Common Side Effects of Biologic Medications
What to expect, what to watch for, and when to contact your healthcare provider
⚠️ Important Safety Note
This page provides general educational information about biologic side effects. It is not a substitute for the full prescribing information for your specific medication. Always read your medication guide and discuss risks with your prescriber and pharmacist.
Most Common Side Effects Across All Biologics
💉 Injection Site Reactions
Redness, swelling, itching, or bruising at the injection site are common, especially when first starting treatment. These usually improve with time and proper injection technique.
🦠 Increased Infection Risk
All biologics that suppress the immune system increase the risk of infections — especially upper respiratory infections. Serious infections (TB, fungal infections) are less common but require immediate medical attention.
😴 Fatigue
Some patients report fatigue, especially during the first weeks of treatment. This often improves as the medication begins to control disease activity.
🤧 Upper Respiratory Infections
Cold-like symptoms and upper respiratory infections are among the most frequently reported side effects of TNF inhibitors and IL-17 inhibitors.
Side Effects by Drug Class
TNF Inhibitors (Humira, Enbrel, Remicade, Simponi, Cimzia)
- Serious infections (TB reactivation, bacterial sepsis, invasive fungal)
- Injection site reactions
- Heart failure worsening (do not use in moderate/severe CHF)
- Lupus-like syndrome (rare)
- Lymphoma and other malignancies (small increased risk)
IL-23 Inhibitors (Skyrizi, Tremfya, Ilumya, Omvoh)
- Upper respiratory infections
- Injection site reactions
- Generally well-tolerated with lower infection risk than TNF inhibitors
IL-17 Inhibitors (Cosentyx, Bimzelx)
- Oral candidiasis (yeast infection of mouth) — especially Bimzelx
- Upper respiratory infections
- Use with caution in inflammatory bowel disease (may worsen IBD)
JAK Inhibitors (Rinvoq, Xeljanz)
- Serious infections
- Thrombosis (blood clots)
- Cardiovascular events (MACE) — especially in older patients with CV risk factors
- Malignancy risk (lymphoma, lung cancer) — black box warning
- Herpes zoster (shingles) reactivation
IL-4/IL-13 Inhibitors (Dupixent)
- Conjunctivitis (eye inflammation) — most common unique side effect
- Injection site reactions
- Generally has a favorable safety profile with no required lab monitoring
When to Call Your Doctor Immediately
- Signs of infection: fever over 100.4°F, chills, persistent cough, painful urination, wounds that won't heal
- Signs of allergic reaction: difficulty breathing, swelling of face/throat, severe rash
- Chest pain, shortness of breath, or signs of blood clot (swelling/pain in one leg)
- Unusual lumps or bumps that persist (monitor for malignancy)
- New or worsening neurological symptoms
- Signs of liver problems: yellowing of skin or eyes, dark urine, severe fatigue
💬 Questions About Your Biologic's Side Effects?
BiologicHealthPlus pharmacists are available 24/7. We can review your medication profile, discuss what to watch for, and coordinate with your prescriber if needed.
Talk to a Pharmacist →📚 Sources & Further Reading
Content developed with reference to leading health organizations, peer-reviewed research, and FDA prescribing information.
Medical Disclaimer: Educational content reviewed by the BiologicHealthPlus Clinical Team. Consult your healthcare provider for personalized advice. Last reviewed: August 2026.