What are the side effects of Lactobacillus bulgaricus?

December 13, 2025 •

4 min read

According to research, Lactobacillus bulgaricus, a probiotic bacterium most commonly known for its role in making yogurt, is generally considered safe for consumption for most healthy individuals. However, like any supplement or food, it can cause side effects, particularly during the initial period of use.

Quick Summary

This article explores the mild digestive issues, rare allergic reactions, and potential risks associated with taking Lactobacillus bulgaricus. It outlines who should be cautious and discusses how to manage common symptoms.

Key Points

Common Side Effects: Mild, temporary digestive issues like gas, bloating, stomach cramps, and changes in bowel movements are the most common side effects as the body adjusts.
Rare Allergic Reactions: In rare cases, allergic reactions can occur, with symptoms like hives, itching, and swelling of the face or throat, which require immediate medical attention.
Risk for Immunocompromised: Individuals with weakened immune systems are at a very low but increased risk for systemic infection from probiotics, and should consult a doctor before use.
Temporary Discomfort: For healthy individuals, any minor digestive discomfort usually subsides within a few days to a week.
Dosage Considerations: While not typically dangerous, taking an excessive amount of probiotics can exacerbate mild side effects like gas and bloating.
Source Matters: Probiotics can be found in fermented foods like yogurt and various supplements, with supplements sometimes containing inactive ingredients that could trigger allergies.
Consult a Doctor: It is essential for individuals with chronic illnesses, pregnant or breastfeeding women, and those on immunosuppressants to consult a healthcare provider before taking probiotics.

Common Side Effects of Lactobacillus bulgaricus

For most people, any side effects from Lactobacillus bulgaricus are mild and temporary as the body adjusts to the new bacterial balance in the gut. These symptoms often resolve within a few days to a week of regular use.

Digestive Discomfort

The most frequently reported side effects are related to digestion. As the new bacteria establish themselves, they can disrupt the existing gut flora, leading to some temporary symptoms. Common issues include gas and bloating due to bacterial fermentation, mild stomach upset or cramping, and temporary changes in bowel movements like diarrhea or constipation. These typically normalize as the gut adapts.

Overdosing on Probiotics

Taking excessive amounts of Lactobacillus bulgaricus can lead to uncomfortable symptoms, potentially worsening minor side effects like bloating and gas. While not a dangerous overdose, adhering to recommended dosages on product labels is important.

Rare and Serious Side Effects

Certain individuals may experience more severe reactions, though these are uncommon, especially for those with pre-existing conditions or compromised immune systems.

Allergic Reactions

Allergic reactions to probiotic supplements, either to the bacteria or other ingredients like soy or lactose, are rare but possible. Symptoms of a serious reaction can include rash, hives, itching, swelling of the face, tongue, or throat, dizziness, and trouble breathing. Immediate medical attention is necessary if these occur.

Risk of Infection

Probiotics are generally safe for healthy individuals and do not cause infections. However, in very rare cases, particularly in those with compromised immune systems, serious infections like bacteremia or septicemia can occur. Those at higher risk include severely ill patients, infants with low birth weight, individuals with central intravenous lines, liver damage, or weakened immune systems (e.g., due to HIV or chemotherapy). Symptoms of infection, such as persistent high fever, chills, or a sore throat, require immediate medical consultation.

Other Potential Reactions

Less frequent adverse reactions can include headaches, nausea, or a metallic taste. Conditions like Cytolytic Vaginosis may be affected by an overgrowth of Lactobacillus species.

Comparison of Side Effects: Lactobacillus Bulgaricus vs. Other Probiotics


Feature	Lactobacillus bulgaricus	Lactobacillus acidophilus	Saccharomyces boulardii
Common Digestive Side Effects	Mild gas and bloating are common initially as the gut adjusts.	Very similar, including gas, bloating, and mild stomach upset.	Gas and constipation may occur. Is a yeast, not a bacterium.
Risk of Allergic Reactions	Rare, but can be triggered by ingredients like soy or lactose if present in the supplement.	Rare, similar to L. bulgaricus, with potential triggers from inactive ingredients.	Allergic reactions are possible, especially for those with yeast sensitivities.
Serious Infection Risk	Very rare, primarily in immunocompromised individuals. Generally non-pathogenic.	Very rare, typically limited to those with weakened immune systems.	Cases of fungemia have been reported, primarily in compromised patients.
Optimal Conditions	Prefers a low pH (4.6–5.4) and warmer temperatures, making it a good fit for fermented milk products.	Tolerates a wide range of conditions, often used in combination with other strains.	Tolerant to antibiotics and stomach acid, making it effective for antibiotic-associated diarrhea.

Who Should Be Cautious?

Certain groups should consult a healthcare provider before taking Lactobacillus bulgaricus supplements or consuming large amounts of fermented foods containing it.

Immunocompromised Individuals: People undergoing chemotherapy, those with HIV/AIDS, or individuals on immunosuppressant medication are at a higher, though still very low, risk for infection.
Seriously Ill or Hospitalized Patients: Those in intensive care, with central lines, or recovering from recent surgery should be monitored closely.
Individuals with Allergies: Anyone with known allergies, especially to lactose or soy, should check the ingredients of probiotic supplements carefully.
Pregnant or Breastfeeding Women: It is always best to consult a doctor before introducing new supplements during pregnancy or breastfeeding.

Conclusion

Lactobacillus bulgaricus is a beneficial probiotic generally safe for healthy individuals, with common side effects being mild, temporary digestive issues. Serious complications are rare and mostly limited to high-risk individuals with compromised immune systems. Consulting a healthcare professional is advisable, especially for those with underlying health conditions or weakened immunity, to ensure safe use. Including it in a balanced diet or through a vetted supplement is typically safe for supporting gut health.

Navigating Probiotic Side Effects

Start with a smaller dose to allow your body to adjust to new bacteria.
If taking a supplement, consider a product with a lower CFU count initially.
Take your probiotic with a meal to minimize potential stomach upset.
Ensure adequate hydration, as this can help mitigate digestive issues.
If side effects persist beyond a few weeks, consider pausing use and speaking with a healthcare provider.
Always inform your doctor about any supplements you are taking, as they may interact with other medications, such as antibiotics.

When to Seek Medical Attention

Seek immediate medical help if you experience signs of a severe allergic reaction, such as: rash, hives, difficulty breathing, or swelling of the face, tongue, or throat.

Contact your doctor if you experience symptoms of a potential infection, such as: high or persistent fever, chills, or a sore throat that does not improve.

Remember, while side effects are possible, the general safety and established benefits of Lactobacillus bulgaricus make it a popular and reliable probiotic for most users.

Resources

For more information on the safety of specific probiotic strains and general guidance on probiotic use, authoritative sources such as the National Institutes of Health (NIH) are highly recommended. Always consult with a healthcare professional before starting any new supplement regimen.

National Center for Complementary and Integrative Health (NCCIH): Provides information on probiotics and health.
American Gastroenterological Association (AGA): Offers resources on digestive health and probiotics.

Following these guidelines can help you enjoy the benefits of Lactobacillus bulgaricus while minimizing the risk of adverse effects.

Frequently Asked Questions

Lactobacillus bulgaricus is a type of probiotic bacterium, a 'good' bacteria, most famously used as a starter culture in the production of yogurt. It aids in the fermentation of milk and is also found in some dietary supplements.

Yes, it is normal to experience temporary gas and bloating when you first start taking Lactobacillus bulgaricus. This is a common side effect as your gut microbiome adjusts to the new bacteria.

For most healthy individuals, any mild side effects, such as gas or bloating, typically last for a few days to a week as the body adapts to the new intestinal flora.

While rare, it is possible to have an allergic reaction, either to the bacteria itself or to other ingredients in a supplement, such as soy or lactose. Symptoms like hives or difficulty breathing require immediate medical help.

It is generally safe for healthy people. However, individuals who are immunocompromised, critically ill, or have central lines should exercise caution and consult a healthcare provider due to a very low risk of infection.

While a serious overdose is highly unlikely, taking more than the recommended dosage can increase the likelihood of mild digestive side effects like gas and bloating. Always follow the product's instructions.

If you experience persistent or worsening side effects, such as a high fever, or your symptoms do not improve after a few weeks, it is recommended to stop taking the probiotic and consult with a doctor.

To minimize side effects, you can start with a smaller dose, take the probiotic with a meal, and ensure you are staying well-hydrated. This helps your digestive system adjust more gradually.

While not common, some sources report that minor side effects can include headaches in isolated cases. These should be temporary if related to probiotic use.