Flare vs. Herx: How to Tell the Difference
One of the most confusing parts of living with Lyme disease is knowing whether you’re having a flare-up of symptoms or a Herxheimer reaction (often called a “Herx”). Both can feel overwhelming, both make you question if your treatment is helping or hurting, and both can look very similar on the surface. But there are important differences that can help you understand what’s happening in your body — and guide your next steps.
What Is a Flare?
A flare happens when existing Lyme symptoms resurface or intensify, usually triggered by stress, environmental exposures, or lifestyle factors. Flares are part of the waxing-and-waning nature of chronic Lyme.
Common flare triggers include:
Physical or emotional stress
Poor sleep or exhaustion
Diet changes (sugar, alcohol, inflammatory foods)
Environmental exposures (mold, chemicals, pollen)
Hormonal changes (menstrual cycle, perimenopause)
Weather shifts
Flares tend to feel familiar — they bring back the same symptoms you’ve had before, sometimes in a more intense way.
What Is a Herxheimer Reaction?
A Herxheimer reaction is different. It occurs when antimicrobial treatments (antibiotics, herbs, or even certain alternative therapies) kill off Lyme bacteria or co-infections. As these pathogens die, they release endotoxins that overwhelm the body’s detox pathways, leading to a temporary worsening of symptoms.
Typical Herx symptoms include:
Sudden spike in fatigue, fever, or chills
Intensified pain or neurological symptoms
Headaches or pressure
Dizziness or worsening brain fog
Anxiety or irritability
Flu-like body aches
Unlike flares, Herxes are directly tied to starting or increasing treatment.
How to Tell Which One You’re Having
Ask yourself:
Did this start after a treatment change? If yes → likely a Herx.
Are my usual triggers present? If yes → likely a flare.
Do symptoms feel familiar or brand-new? Flares often repeat patterns; Herxes may bring sudden, new layers.
Am I improving after detox measures? If yes, that points to a Herx.
Managing a Flare
During a flare, the goal is to remove triggers and reduce inflammation:
Prioritize rest and sleep.
Return to a cleaner, lower-inflammatory diet.
Minimize stress (meditation, journaling, breathing exercises).
Support your immune system with supplements recommended by your provider.
Managing a Herx
During a Herx, the goal is to support detox and reduce die-off intensity:
Lower or pause treatment temporarily (with provider guidance).
Stay hydrated and add electrolytes.
Use detox binders (activated charcoal, bentonite clay, cholestyramine — as directed).
Sweat gently if tolerated (sauna, epsom salt baths).
Support liver and lymphatic drainage (milk thistle, gentle movement, dry brushing).
Why It Matters
Understanding the difference between a flare and a Herx can prevent unnecessary panic — and help you respond appropriately. If it’s a flare, you focus on triggers and lifestyle adjustments. If it’s a Herx, you focus on detox and treatment management.
Both can feel discouraging, but neither means you’re moving backward. In fact, Herxing is often a sign that treatment is working — even if it feels miserable in the moment.
Lyme disease recovery is rarely a straight line. Learning to recognize whether you’re experiencing a flare or a Herxheimer reaction can give you back a sense of control in the chaos.
If in doubt, always check in with your Lyme-literate provider to guide your next steps. Healing is possible — and understanding your body’s signals is part of the journey.