What illness is smelling rotten eggs? Uncovering the Underlying Causes

September 23, 2025 •

4 min read

The unpleasant odor of rotten eggs is typically caused by hydrogen sulfide gas, which can be a byproduct of digestion. While sometimes related to diet, a persistent or concerning smell can signal an underlying health issue. This guide explores the answer to the question, what illness is smelling rotten eggs?

Quick Summary

The rotten egg smell can be linked to digestive issues like SIBO, gastroparesis, H. pylori, or Giardia infection, caused by excess hydrogen sulfide. In some cases, it can be a neurological disorder like phantosmia, or a rare metabolic condition known as TMAU.

Key Points

Hydrogen Sulfide Gas: The rotten egg smell is most commonly caused by excess hydrogen sulfide ($H_2S$) gas, a byproduct of bacterial activity in the digestive tract.
Gastrointestinal Causes: Digestive disorders such as Small Intestinal Bacterial Overgrowth (SIBO), gastroparesis, and infections like Giardia or H. pylori are primary culprits.
Neurological Conditions: In some cases, the smell can be a phantom sensation (phantosmia) or a distorted smell perception (parosmia), often linked to respiratory infections or head injury.
Dietary Triggers: High-sulfur foods like eggs, broccoli, and red meat can contribute to the odor, as can alcohol and carbonated drinks.
Rare Conditions: A persistent, foul body odor including a rotten egg smell can, in rare instances, be a symptom of Trimethylaminuria (TMAU), a genetic metabolic disorder.
When to See a Doctor: Persistent or severe symptoms, including abdominal pain, weight loss, or chronic digestive upset, warrant a medical evaluation to rule out a serious underlying condition.

Causes of Excessive Hydrogen Sulfide Production

Hydrogen sulfide ($H_2S$) is a gas produced by bacteria in the digestive tract, particularly when breaking down sulfur-rich foods. A normal amount is odorless, but an overproduction can lead to unpleasant smells associated with burps (sulfur burps), flatulence, or even breath. While diet is a major contributor, an underlying health problem can exacerbate this production.

Gastrointestinal Conditions

Several conditions affecting the digestive system can lead to an increase in hydrogen sulfide gas:

Small Intestinal Bacterial Overgrowth (SIBO): In SIBO, an abnormally large number of bacteria, including those that produce hydrogen sulfide, colonize the small intestine. This can lead to bloating, diarrhea, gas, and foul-smelling burps.
Giardia Infection: This intestinal infection is caused by the Giardia parasite, often contracted from contaminated water. A classic symptom is burps with a strong sulfur odor, accompanied by diarrhea, fatigue, and abdominal cramps.
Gastroparesis: Also known as stomach paralysis, this condition slows or stops the movement of food from the stomach to the small intestine. The prolonged presence of food in the stomach allows bacteria to ferment and produce excess gas, including $H_2S$.
H. pylori Infection: The Helicobacter pylori bacterium is a common cause of peptic ulcers and can cause inflammation in the stomach lining. This can lead to digestive upset, including sulfur burps, bloating, and heartburn.
Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD): These chronic digestive disorders can disrupt the balance of gut flora and affect motility, contributing to increased gas and odor.

Neurological and Sensory Disorders

Sometimes, the rotten egg smell isn't from the digestive system but is a sensory hallucination known as phantosmia. This condition involves smelling an odor that isn't actually present.

Phantosmia: This olfactory hallucination can cause a person to detect foul odors like rotten eggs, sewage, or burnt toast. Potential causes include head injury, sinus infections, and viral infections like COVID-19.
Parosmia: Similar to phantosmia, parosmia is a distorted sense of smell where an actual odor is perceived as different, often unpleasant. A pleasant smell might be perceived as a rotten one. This can follow a severe respiratory infection, especially COVID-19.

Other Systemic Causes

In less common scenarios, the odor can point to other health issues.

Trimethylaminuria (TMAU): Also known as 'fish odor syndrome,' this rare genetic metabolic disorder prevents the body from breaking down trimethylamine. While often described as smelling fishy, some people experience a rotten egg or garbage-like smell through their sweat, urine, and breath. For more information, you can visit the National Organization for Rare Disorders (NORD).
Severe Liver or Kidney Disease: In rare instances, severe liver or kidney disease can cause a buildup of toxins in the body, which can be released through the breath and cause foul odors.

When to See a Doctor

While occasional sulfur burps are often harmless, you should see a doctor if the symptom is persistent, recurring, or accompanied by other worrying symptoms. Consult a healthcare provider if you experience:

Severe abdominal pain, cramps, or bloating.
Chronic diarrhea or constipation.
Unexplained weight loss.
Fever, nausea, or vomiting.
A persistent phantom smell not related to diet.
Signs of dehydration from digestive issues.

Managing and Treating the Symptom

Treatment for the rotten egg smell depends entirely on the underlying cause. If it's a dietary issue, simple adjustments can help. For medical conditions, targeting the root cause is necessary.

Dietary and Lifestyle Changes:

Reduce Sulfur-Rich Foods: Limit intake of high-sulfur foods like broccoli, cauliflower, cabbage, onions, garlic, eggs, and red meat.
Eat Smaller, Frequent Meals: This can aid digestion and prevent food from lingering too long in the stomach.
Stay Hydrated: Drinking plenty of water supports proper digestion and can flush out toxins.
Limit Carbonated Drinks: Avoid sodas and seltzers, which add excess gas to your digestive system.
Consider Probiotics: Probiotics can help restore a healthy balance of bacteria in your gut.

Medical Interventions:

Medication: For infections like H. pylori or Giardia, antibiotics or antiprotozoal drugs are prescribed. Medications for gastroparesis can stimulate stomach muscles.
Addressing Underlying Conditions: Managing chronic conditions like IBS or GERD is crucial to controlling the symptom.
Neurological Treatment: For phantosmia, treatment focuses on the underlying cause, which may include addressing a sinus infection or other condition.

Comparison of Illnesses and Symptoms


Illness/Condition	Rotten Egg Smell Cause	Other Common Symptoms
SIBO	Bacterial overgrowth producing $H_2S$	Bloating, gas, diarrhea, abdominal pain
Giardiasis	Parasitic infection	Diarrhea, cramps, nausea, fatigue, weight loss
Gastroparesis	Slowed digestion, bacterial fermentation	Nausea, vomiting, bloating, feeling full quickly
*H. pylori*	Bacterial infection in stomach	Heartburn, bloating, abdominal pain, nausea
Phantosmia	Olfactory hallucination (brain issue)	None directly, associated with head injury, infections
TMAU	Inability to break down trimethylamine	Body odor in sweat, urine, breath (can be fishy)
Severe Liver Disease	Buildup of toxins in body	Jaundice, fatigue, swelling in abdomen, nausea

Conclusion

While a rotten egg smell can often be traced back to diet, it's essential to consider the possibility of an underlying medical condition, especially if the symptom is persistent or accompanied by other health issues. By understanding the potential causes—from bacterial infections and digestive disorders to neurological issues and rare genetic conditions—individuals can take the first step toward finding relief. Always consult a healthcare professional for a proper diagnosis and treatment plan to ensure your health concerns are addressed effectively.

Frequently Asked Questions

Foods high in sulfur, such as eggs, red meat, broccoli, cauliflower, and onions, can cause sulfur burps when bacteria in your gut break them down. Dairy products and alcohol can also contribute.

Occasional sulfur burps are usually harmless and diet-related. However, frequent or persistent sulfur burps, especially with other symptoms like severe abdominal pain or weight loss, could indicate a more serious underlying condition like SIBO or an infection.

Yes, stress and anxiety can affect the digestive system and disrupt the balance of gut bacteria, potentially leading to increased gas production and sulfur burps. Managing stress is an important step in improving gut health.

COVID-19 can damage the olfactory system, leading to parosmia (distorted smells) or phantosmia (phantom smells). This damage can cause pleasant odors to smell foul or for a rotten egg-like odor to appear without any trigger.

A Giardia infection, which can cause sulfur burps, is treated with prescribed antiprotozoal medication. A doctor will need to diagnose the infection first, typically with a stool test.

Probiotics can help rebalance the gut microbiome by introducing beneficial bacteria. For some people, this can help reduce the overgrowth of sulfide-producing bacteria and alleviate symptoms.

Phantosmia is a phantom smell, meaning you smell something that isn't there, like burnt toast or rotten eggs. Parosmia is a distorted smell, where an actual scent, like coffee, smells unpleasant or foul.