Hydrogen Sulphide SIBO Symptoms & Treatment

If you’ve been diagnosed with SIBO and treated it… But if you’re still dealing with bloating, loose stools, food reactions, or that distinctive “rotten egg” gas smell, you may be dealing with hydrogen sulphide SIBO.

For people with chronic gut issues, irritable bowel syndrome (IBS), or treatment-resistant SIBO, this subtype can be the missing piece. Let’s break down what hydrogen sulphide SIBO is, how it’s different, and what you can do about it.

What is Hydrogen Sulphide SIBO?

Small intestinal bacterial overgrowth (SIBO) occurs when bacteria overgrow in the small intestine and ferment carbohydrates, producing gases.

Traditionally, we talk about:

• Hydrogen-dominant SIBO, which is more diarrhoea-dominant

• Methane-dominant SIBO, which is more constipation-dominant

But more recently, hydrogen sulphide SIBO has been recognised as a third subtype. Instead of producing hydrogen or methane, certain bacteria produce hydrogen sulphide (H₂S).

Hydrogen sulphide is naturally produced in small amounts in the body. But in excess, it can:

• Damage the gut lining

• Impair mitochondrial function – the energy centre of the cell

• Trigger inflammation

• Aggravate IBS symptoms

• Worsens histamine intolerance and mast cell activation

For people with chronic gut dysfunction, this subtype can be particularly inflammatory.

Common symptoms of Hydrogen Sulphide SIBO

If you already know you have SIBO but your symptoms don’t “fit” typical hydrogen or methane patterns, look for:

• Persistent bloating

• Loose stools or diarrhoea

• Urgency

• Rotten egg–smelling gas

• Sensitivity to sulphur foods (eggs, garlic, onions, and brassicas like broccoli, cauliflower, kale, cabbage or bok choy)

• Reactions to supplements like N-acetyl cysteine (NAC) or glutathione

• Brain fog and fatigue

• Food chemical sensitivities, such as histamine or salicylates

• Burning or irritated gut sensation

Unlike methane SIBO (often constipation-dominant), hydrogen sulphide SIBO is more commonly associated with diarrhoea-predominant IBS.

Why is Hydrogen Sulphide SIBO often missed?

Many older breath tests only measured hydrogen and methane. Hydrogen sulphide wasn’t directly measured, which meant:

• Hydrogen levels might appear “low”

• Methane may be absent

• Yet symptoms remain significant

Clinically, some practitioners suspect hydrogen sulphide SIBO when:

• Hydrogen readings are unusually low

• Symptoms are inflammatory and diarrhoea-based

• There is strong sulphur intolerance

What causes Hydrogen Sulfide SIBO?

The root drivers are often the same as those of other SIBO types:

• Poor motility - impaired migrating motor complex, which is often associated with many gut conditions, including IBS and SIBO

• Post-infectious IBS

• Chronic stress

• Hypothyroidism

• Low stomach acid

• Pancreatic insufficiency

• Structural issues like adhesions and endometriosis

But hydrogen sulphide SIBO is particularly influenced by:

• High sulphur diets

• Excess animal protein

• Sulphur-containing supplements

• Impaired sulphur metabolism pathways

• Dysbiosis involving sulphate-reducing bacteria

If you’ve been following a high-protein, high-garlic, high-brassica “gut health” diet and symptoms worsened, this subtype may be relevant.

The connection between Hydrogen Sulphide, Histamine and Mast Cells

Many patients with hydrogen sulphide SIBO also experience:

• Histamine intolerance

• Mast cell activation symptoms

• Salicylate sensitivity

• Chemical sensitivities

Hydrogen sulphide is inflammatory to the gut lining. When the intestinal barrier becomes irritated:

• Mast cells become activated

• Diamine oxidase (DAO) function may be impaired, increasing histamine in the body

• Histamine clearance decreases

• Food reactions worsen

This is why some people feel worse on fermented foods, bone broth, or high-sulphur “gut healing” protocols.

Treatment approach for Hydrogen Sulphide SIBO

Treatment needs to be individualised, but generally involves:

1. Reducing sulphur load (temporarily)

This does not mean lifelong restriction. It may include short-term reduction of:

• Garlic and onions

• Eggs

• Cruciferous vegetables

• High-sulphur supplements (like NAC, MSM, and glutathione)

• Excess animal protein

2. Targeted Antimicrobials

Specific herbal or pharmaceutical antimicrobials may be used under practitioner supervision if you can tolerate them.

3. Supporting sulphur metabolism

Some patients benefit from:

• Molybdenum

• B vitamins

• Epsom salt baths (cautiously)

• Gentle liver support

4. Repairing the gut lining

After reducing overgrowth, rebuilding is essential:

• Butyrate support

• Zinc carnosine

• Slippery elm

• Specific probiotics (carefully selected to be low histamine producers)

5. Restoring motility

Without motility support, SIBO frequently relapses. This may involve:

• Prokinetics

• Stress regulation

• Thyroid optimisation

• Structured meal spacing

Why treating Hydrogen Sulphide SIBO is different

Many people feel worse on standard SIBO protocols because:

• They are high in sulphur foods

• They rely heavily on garlic-based antimicrobials

• They don’t address inflammatory load

If your bloating improved but diarrhoea, urgency or chemical sensitivities worsened, the treatment may not have matched your subtype.

Final Thoughts

If you have chronic gut issues, diarrhoea-predominant IBS, persistent SIBO, or unexplained sulphur sensitivity, hydrogen sulphide SIBO is worth exploring.

The key is not just “killing bacteria” but:

• Reducing inflammation

• Supporting detoxification pathways

• Rebuilding gut resilience

• Restoring motility

When treated correctly, many patients notice:

• Reduced bloating

• Improved stool consistency

• Fewer food reactions

• Better energy and mental clarity

If your SIBO journey has stalled, this subtype could be the missing link.