When I was diagnosed with Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) — specifically the rare Lewis-Sumner variant — in 2022, immunoglobulin therapy became part of my life.
I started with IVIg.
Recently, I switched to SCIg.
Both treatments help (read here) slow disease progression and stabilize symptoms.
Both can improve quality of life.
And both can come with side effects.
If you’re wondering:
- Are IVIg side effects normal?
- Is SCIg easier on the body?
- How long will this headache last?
- Why do I feel like I have the flu after infusion?
You’re not alone.
This guide walks you through what to expect, what’s considered normal, what deserves medical attention, and how to make treatment gentler on your body.
Why Do IVIg and SCIg Cause Side Effects?
Immunoglobulin therapy is made from donated human plasma. These antibodies are purified and concentrated into medication that helps regulate the immune system.
It comes as a thick, slightly oily/sticky fluid — basically a concentrated antibody solution designed to be absorbed slowly and safely.
This texture can contribute to some of the side effects you might notice, like bloating or tenderness at injection sites.
When infused, several things may happen:
- Your immune system responds to the incoming antibodies
- Fluid shifts occur
- Inflammation pathways temporarily activate
- Blood viscosity can change
For a body already navigating autoimmunity, that’s a lot to process.
Most reactions are not dangerous. They’re simply your system adjusting.
And for many patients, they lessen over time.
Common Side Effects After IVIg Infusions
IVIg (intravenous immunoglobulin) is delivered directly into the bloodstream, usually every 3–4 weeks. Because it enters the system quickly and in larger volumes, systemic side effects are more common.
🟦 Headache
One of the most frequently reported side effects. It can range from mild pressure to migraine-level intensity, especially if the infusion runs too fast. In rare cases, severe headache with neck stiffness may indicate aseptic meningitis.
IVIg was particularly difficult for me when it came to headaches. Sometimes I could manage with Advil, but other times I needed something stronger, prescribed by a doctor and available in the hospital. Not nice.
🟦 Fatigue
A deep, heavy “crash” feeling. Some people need a full day (or two) of rest afterward.
Yes, I confirm. Fatigue is ALWAYS here for you – very loyal.
🟦 Flu-like symptoms
Chills, low-grade fever, muscle aches, flushed face — the “am I getting sick?” sensation.
Yes, they happen. I had those on a few occasions, but not always, and not overwhelming.
🟦 Nausea or upset stomach
Usually mild to moderate.
I sometimes had nausea but don’t recall upset stomach.
🟦 Dizziness or tremor
Feeling wobbly or shaky — especially frustrating when neuropathy is already part of daily life.
I usually felt like I was walking on cotton—unsteady, soft, and not quite grounded.
🟦 Back or neck stiffness
Tightness and soreness after infusion are commonly mentioned in patient communities.
Never – thank God – had any of it.
🟦 Rare but serious reactions
Uncommon but important to know:
- Blood clots
- Kidney strain
- Aseptic meningitis
- Severe allergic reactions
Most IVIg side effects resolve within 24 to 72 hours.
If they don’t go away or feel severe, contact your healthcare team.
Common Side Effects After SCIg Injection
SCIg (subcutaneous immunoglobulin) is injected under the skin, typically weekly. Because it absorbs more slowly, systemic reactions are generally milder.
🟦 Stomach bloating
Stomach bloating is the first and most noticeable side effect. The size of the “bloat” depends on how much immunoglobulin is injected under the skin, and the swelling can last 24 to 72 hours as the medication absorbs.
It can look dramatic — especially in the beginning — but it does go down.
Also—I won’t lie—this bloated stomach can be painful. Especially since I chose a once-a-month infusion, which means there’s a lot of fluid sitting under the skin in my abdomen. It can be really uncomfortable, particularly when I’m trying to fall asleep.
I do take a painkiller. I’ve tried to manage without it, but the fatigue the next morning—from both the pain and lack of sleep—was just too much.
🟦 Injection site reactions
Redness, swelling, itching, tenderness, or bruising at the injection area. Very common in the first few weeks.
Some patients also report allergic reactions to the adhesive used to secure the needles.
I also want to add that in Facebook support groups, I’ve seen some pretty intense injection-site reactions, and people understandably panic when they experience them.
So far, I’ve been lucky (knock on wood) and haven’t had any myself.
That said, I’m aware this could change over time. As my body changes and my illness progresses, new challenges can appear. Chronic illness is never static—it’s a constantly evolving situation, and that uncertainty can be stressful.
🟦 Headache
Possible, but typically milder than with IVIg.
🟦 Fatigue
Usually less intense and shorter in duration compared to IVIg.
Sometimes I get through infusions just fine—other times, not so much. With IVIg, I used to have debilitating headaches. SCIg, on the other hand, seems to leave me extremely fatigued—I feel like I need a nap every ten minutes the next day.
Still, I try to stay determined and keep moving as much as I can, just to get my “juices” flowing and help the immunoglobulins absorb more efficiently. It’s a constant balancing act—and honestly, a bit of a struggle.
🟦 Mild flu-like symptoms
Occasional low-grade fever or nausea.
🟦 Rare but serious reactions
Serious systemic reactions are very rare with SCIg, but severe allergies can occur.
For many long-term patients, SCIg becomes easier as the body adjusts.
And that’s the good news that I can confirm.
Comparison Table: IVIg vs. SCIG Side Effects
| Side Effect Category | IVIg (Intravenous) | SCIg (Subcutaneous) | Notes |
|---|---|---|---|
| Systemic Reactions (e.g., headache, fatigue, flu-like) | Common (up to 49%), more severe | Less common, milder | SCIg slower absorption reduces intensity |
| Local Reactions | Rare (IV site irritation) | Common (redness, swelling, itching; 23%) | Decrease over time with SCIg |
| Headache Severity | Often severe, aseptic meningitis risk | Mild | IVIg: 1-2 days post-infusion |
| Fatigue Duration | 1-3 days, “crash” | Shorter, less profound | Both improve with premeds |
| Serious Risks (clots, kidney) | Higher (thromboembolism, renal) | Very low (0.3/100 person-years) | Hydration key for both |
| Frequency of Effects | Per infusion (every 3-4 weeks) | Per injection (weekly), but local only | Tolerance builds faster with SCIg |
This table for me highlights SCIg’s edge in systemic safety for long-term management of CIDP.
How to Make Immunoglobulin Treatment Easier on Your Body
🟦 Hydrate well
Drinking plenty of water the day before, the day of, and the day after infusion can dramatically reduce headaches and fatigue.
(Link to my post on hydration for immunoglobulin therapy here)
🟦 Slow the infusion rate
Faster isn’t better. Slower infusions often mean fewer side effects.
🟦 Consider pre-medication
Some patients benefit from:
- Acetaminophen
- Ibuprofen
- Antihistamines (e.g., diphenhydramine)
Always consult your doctor first.
🟦 Gentle temperature therapy
Warm compresses soothe soreness. Avoid ice for up to 4 hours after injection.
🟦 Plan recovery time
Schedule lighter activities post-treatment. Rest is part of the process.
🟦 keep a diary
Log injections, reactions, and patterns. This helps you rotate sites, adjust doses, and flag anything extreme (like blistering) to your healthcare team.
🟦 Comfort measures
Wear comfortable loose clothing, keep your drinks, food, snacks, and even remote controllers, phones, and tablets within reach.
🟦 take care of your injection sites (SCIg)
Rotate spots — abdomen, thighs, arms — to give your tissue a break. Gently massage the area after injecting to help with soreness.
🟦 Adjust your technique (SCIg)
Smaller needles can make injections more comfortable. Hyaluronidase (if prescribed) can help the medicine absorb more smoothly.
🟦 Gentle massage (SCIg)
Lightly massage the area after injection to reduce swelling
When to Seek Medical Help
Contact your healthcare provider if you experience:
- Fever above 101°F (38.3°C)
- Severe headache lasting more than 48 hours
- Chest pain or shortness of breath
- Sudden leg swelling
- Severe neck stiffness
- Signs of injection site infection (spreading redness, pus, fever)
- Hives, throat swelling, dizziness
Most side effects are manageable — but serious symptoms should never be ignored.
Frequently Asked Questions About IVIg and SCIg Side Effects
Are IVIg side effects normal in CIDP?
Yes. Headaches, fatigue, and flu-like symptoms are common, especially during early infusions. Many patients see improvement over time.
How long do IVIg side effects last?
Most resolve within 24 to 72 hours. Persistent or worsening symptoms should be evaluated.
Is SCIg safer than IVIg?
SCIg generally causes fewer systemic reactions because it absorbs more slowly. Local injection site reactions are common.
Why does IVIg cause headaches?
Possible reasons include fluid shifts, immune activation, and changes in blood thickness. Slower infusion rates and hydration help reduce severity.
Do side effects improve over time?
For many patients, yes. The body often adapts after several cycles.
When should I worry about side effects?
Seek immediate care for severe headache with neck stiffness, chest pain, high fever, sudden swelling, or severe allergic reactions.
The Emotional Side of Immunoglobulin Therapy
Immunoglobulin treatment is made from donated plasma. That’s extraordinary — and intense.
It’s not a transplant, but it is a significant physiological load for your body, especially when autoimmunity is involved.
If your system reacts sometimes, it doesn’t mean you’re weak — it means your body is processing something substantial.
I’d say that if you are on IVIg and need to stay in the hospital frequently, depending on your schedule, there is an issue adding to the emotional toll of Ig therapy, and that is hospital stress and IVIg infusions.
There are also coping strategies you can adapt to make it easier.
Finding Support as You Navigate CIDP Treatment
Undergoing IVIg or SCIg treatment can feel deeply isolating.
Because CIDP is a rare disorder, chances are there aren’t many people in your immediate circle who you can just hang out with and chat about your struggles.
For a long time, I tried to navigate it on my own.
Eventually, I joined a few Facebook support groups.
It wasn’t an easy decision.
I hesitated for psychological reasons — I was afraid of being overwhelmed by information, afraid of absorbing too many worst-case stories.
I also worried I wouldn’t quite fit in, because my variant isn’t as severe as some others, and I struggled with a quiet sense of impostor syndrome.
After a while, I realized I needed to get my ducks in a row — because going through this alone just sucks.
One day a simple thought surfaced: you don’t have to go through this alone.
(it wanted to surface for a while I was just pushing it down)
This connection, even imperfect, turned out to matter more than those fears.
So here’s a pearl of wisdom from slightly neurotic/overthinking chronic illness warrior: if you’re feeling overwhelmed, anxious, or unsure about side effects, a support group can make a real difference.
There are many patient-led support groups on Facebook specifically for:
- CIDP warriors sharing experiences and tips
- People receiving IVIg or SCIg for other autoimmune or neurological conditions
Their lived experience — navigating injections, managing fatigue, dealing with bloating, and figuring out what works for their bodies — is often priceless.
You can also learn about techniques that helped others tolerate treatment, such as hydration strategies, gentle movement, or stress-reduction practices.
These communities offered me real-world advice, coping strategies, and emotional support from people who understand what I am going through.
Tip: Look for groups with active moderation and verified members to ensure a safe, supportive environment.
Final Thoughts
Those of us living with chronic illness often become hypervigilant.
Mostly about..
well…
E-V-E-R-Y-T-H-I-N-G our health&body related.
And can we really be blamed?
When your body feels unpredictable, paying close attention becomes a form of self-protection.
It can be exhausting to live in that heightened state.
But there’s also some benefit to it.
Hypervigilance helps us notice subtle changes, track progression, and recognize what’s working — and what isn’t.
It teaches us how to adjust our mindset, our routines, our diet, and the way we move through each day.
From my experience, staying open to adjustments, paying attention to your body’s reactions, and being gentle with yourself can guide you.
Your body is taking in a lot, and kindness helps it cope.
And finally, remember this: small but consistent steps can make a big difference.
After all, the turtle — chosen as a symbol of chronic illness — was picked for a reason.
Take a moment to think about it, and let it inspire patience, resilience, and gentle progress along your journey.
A small note: I’m sharing my personal experience as someone living with CIDP, not as a medical professional—always trust your own body and consult a qualified healthcare provider for medical advice.
Sharing is caring – if this supported you in any small way, sharing it may support someone else with CIDP, and subscribing keeps this circle of healing and awareness growing.
Sources
- https://www.neuro-outaouais.com/medical-complications-associated-with-chronic-ivig-use/
- https://csprx.com/pharmacy-blog/ivig-treatment-for-cidp/
- https://www.nufactor.com/resources/ig/articles/ar-a-comparative-look-at-ivig-and-scig.html
- https://ameripharmaspecialty.com/ar/other-health-conditions/ivig-for-cidp/
- https://www.gammagard.com/cidp/ivig-side-effects
- https://www.blood.gov.au/sites/default/files/documents/2025-02/Immunoglobulin%20products%20for%20CIDP.PDF
- https://jnnp.bmj.com/content/95/Suppl_2/A37.4
- https://ameripharmaspecialty.com/ivig/understanding-the-common-side-effects-of-ivig-treatment/
- https://www.hyqvia.com/cidp
- https://www.pharmacytimes.com/view/video-mitigating-adverse-events-in-ivig-therapy-for-cidp-is-key-role-of-care-team
- https://pmc.ncbi.nlm.nih.gov/articles/PMC12085551/
- https://www.allergy.org.au/patients/immunodeficiencies/scig-therapy-general-information
- https://www.aaaai.org/allergist-resources/ask-the-expert/answers/2021/ivigss
- https://inpharmd.com/inquiries/12293
- https://forum.livingwithpolyneuropathy.org/t/scig-from-ivig-and-more-side-effects/138
- https://forum.gbs-cidp.org/forums/topic/odd-side-effect/
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