Drug & supplement interaction

Bifidobacterium Animalis Subsp. Lactis + Acyclovir

Acyclovir brand names: Zovirax, Zovirax Injection, Sitavig, Avaclyr.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Bifidobacterium Animalis Subsp. Lactis and Acyclovir in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Bifidobacterium Animalis Subsp. Lactis and Acyclovir

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Acyclovir and Bifidobacterium Animalis Subsp. Lactis in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Bifidobacterium Animalis Subsp. Lactis safety at a glance

Bifidobacterium An... overall Generally safe Generally well tolerated by most healthy people when taken as directed.
Pregnancy Use caution Often considered low-risk, but evidence is limited, so check with your doctor first.
Breastfeeding Use caution Likely low-risk but not well studied; discuss with your healthcare provider.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Acyclovir and Bifidobacterium Animalis Subsp. Lactis? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Acyclovir

Interactions in our licensed database are recorded against drug classes, not just single drug names. Acyclovir is filed under 6 classifications — including organic anion transporter 1 (oat1) substrates, topical drugs, nephrotoxic drugs. Bifidobacterium Animalis Subsp. Lactis has documented interactions with 1 drug class — the most serious being antibiotic drugs (moderate) — and none of Acyclovir’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Bifidobacterium Animalis Subsp. Lactis Does Interact With Other Medications

Bifidobacterium Animalis Subsp. Lactis has 182 moderate known drug interactions in our database — Acyclovir isn’t one of them. If you take anything else, check it against the full list below.

Moderate 182 No known interaction 2,648 (incl. Acyclovir)
Taking anything else?

Check Another of Your Medications Against Bifidobacterium Animalis Subsp. Lactis

Covers the 2,830 medications we’ve checked against Bifidobacterium Animalis Subsp. Lactis. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Bifidobacterium Animalis Subsp. Lactis and Acyclovir May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do. One of them is worth acting on rather than waiting out — marked below.

  • A higher chance of infection Worth acting on reported in 5.0% of FDA reports for Acyclovir Additional detail

    Bifidobacterium Animalis Subsp. Lactis

    “Orally, Bifidobacterium lactis seems to be well tolerated by most patients.

    Most Common Adverse Effects:

    Orally: Diarrhea.

    Serious Adverse Effects (Rare):

    Orally: There is concern that probiotics may cause infections in some people.”

    Bifidobacterium Animalis Subsp. Lactis · Natural Medicines adverse-effect record, reported in diarrhea.

    Acyclovir

    Listed in the ADVERSE REACTIONS section of the FDA label for Acyclovir, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

  • Stomach pain Additional detail

    Bifidobacterium Animalis Subsp. Lactis

    “Bloating and flatulence have been reported with probiotic use; however, these adverse effects have not been reported from ingestion of Bifidobacterium lactis in particular. When taken orally, B. lactis can cause diarrhea and other gastrointestinal complaints in children. Gastrointestinal complaints including worsening diarrhea, abdominal pain, constipation, stomach burn, and flatulence have been reported rarely.”

    Bifidobacterium Animalis Subsp. Lactis · Natural Medicines adverse-effect record, reported in constipation.

    5 sources cited
    1. 3169. Phuapradit P, Varavithya W, Vathanophas K, et al. Reduction of rotavirus infection in children receiving bifidobacteria-supplemented formula. J Med Assoc Thai 1999;82:S43-8.
    2. 95381. Taipale TJ, Pienihäkkinen K, Isolauri E, Jokela JT, Söderling EM. Bifidobacterium animalis subsp. lactis BB-12 in reducing the risk of infections in early childhood. Pediatr Res. 2016;79(1-1):65-9. PubMed
    3. 105149. Amat-Bou M, Garcia-Ribera S, Climent E, et al. Effects of Bifidobacterium animalis Subsp. lactis (BPL1) supplementation in children and adolescents with prader-willi syndrome: A randomized crossover trial. Nutrients. 2020;12(10):3123. PubMed
    4. 110986. Mäkelä SM, Forssten SD, Kailajärvi M, et al. Effects of Bifidobacterium animalis ssp. lactis 420 on gastrointestinal inflammation induced by a nonsteroidal anti-inflammatory drug: A randomized, placebo-controlled, double-blind clinical trial. Br J Clin Ph
    5. 110999. Wildt S, Munck LK, Vinter-Jensen L, et al. Probiotic treatment of collagenous colitis: a randomized, double-blind, placebo-controlled trial with Lactobacillus acidophilus and Bifidobacterium animalis subsp. Lactis. Inflamm Bowel Dis 2006;12(5):395-401. PubMed

    Acyclovir

    Listed in the ADVERSE REACTIONS section of the FDA label for Acyclovir. Read the label on DailyMed ›

  • A skin rash reported in 3.7% of FDA reports for Acyclovir Additional detail

    Bifidobacterium Animalis Subsp. Lactis

    “In clinical research, two cases of rash, one with itching, were reported by patients taking a combination of Bifidobacterium lactis BB-12, Lacticaseibacillus paracasei F19, and Lactobacillus acidophilus La5. However, it is not clear if these adverse effects were due to B. lactis, other probiotics, or the combination, or if the events were idiosyncratic.”

    Bifidobacterium Animalis Subsp. Lactis · Natural Medicines adverse-effect record, reported in pruritus.

    1 source cited
    1. 90236. Begtrup LM, de Muckadell OB, Kjeldsen J, Christensen RD, Jarbøl DE. Long-term treatment with probiotics in primary care patients with irritable bowel syndrome--a randomised, double-blind, placebo controlled trial. Scand J Gastroenterol 2013;48(10):1127-35 PubMed

    Acyclovir

    Listed in the ADVERSE REACTIONS section of the FDA label for Acyclovir, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

Reported for Bifidobacterium Animalis Subsp. Lactis but not commonly for Acyclovir: constipation, bloating or gas, diarrhea and itching.

Effects for Acyclovir come from the ADVERSE REACTIONS section of its FDA label; effects for Bifidobacterium Animalis Subsp. Lactis come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 114,761 voluntary FDA FAERS reports for Acyclovir that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

From our Q&A

Questions About Bifidobacterium Animalis Subsp. Lactis or Acyclovir

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Bifidobacterium Animalis Subsp. Lactis or Acyclovir, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Acyclovir

This page covers Bifidobacterium Animalis Subsp. Lactis only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Acyclovir page lists 37 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Asarabacca (major), Siberian Cocklebur (major), African Wild Potato (moderate) and Aristolochia (moderate).

By severity: 3 major · 23 moderate · 11 minor.

From our pharmacist’s overview on the Acyclovir page

“Kidney strain is the risk to understand first. Acyclovir (Zovirax) can stress the kidneys on its own, and a few ingredients here, Siberian cocklebur especially, are toxic to kidney tissue, so pairing them could compound the harm.”

Reviewed by 2 · Jul 18, 2026

Open the Acyclovir interaction page

How much people look this up

Where Bifidobacterium Animalis Subsp. Lactis and Acyclovir Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Bifidobacterium Animalis Subsp. Lactis
Steady interest

#1,405 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Acyclovir
Top 5%

#59 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Bifidobacterium Animalis Subsp. Lactis reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Bifidobacterium Animalis Subsp. Lactis and Acyclovir records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Bifidobacterium Animalis Subsp. Lactis

What is Bifidobacterium Animalis Subsp. Lactis?

  • Digestive health and regularity
  • Constipation relief
  • Immune support
  • Antibiotic-associated diarrhea
  • General gut microbiome balance

Bifidobacterium animalis subsp. lactis is a well-studied probiotic bacterium commonly added to supplements and yogurts to support digestion and gut health. It appears generally safe for most healthy people, with the best evidence for improving bowel regularity, but benefits vary by person and strain. Talk with your pharmacist or doctor before starting it, especially if you have a weakened immune system or a serious illness.

Bifidobacterium animalis subsp. lactis · Bifidobacteriaceae · Live bacterial cells (probiotic strain) · Capsules, tablets, powders, sachets, fermented dairy products like yogurt, and combination probiotic supplements

An interaction check asks whether these two react with each other — it does not ask whether Bifidobacterium Animalis Subsp. Lactis is a good idea for someone in your situation. Here is what our Bifidobacterium Animalis Subsp. Lactis record says about it on its own.

Bifidobacterium Animalis Subsp. Lactis: dosing

There is no single standardized dose of B. lactis that works for everyone. Probiotic doses are usually measured in colony-forming units (CFU), and the amount varies widely between products.The best approach is to follow the directions on the product label and start with the lowest suggested amount. They can help you pick a reputable product and decide whether a probiotic is appropriate for your situation.

From our Bifidobacterium Animalis Subsp. Lactis monograph — the full record covers uses, side effects and every documented interaction.

Read the full Bifidobacterium Animalis Subsp. Lactis monograph & all interactions
Medication

About Acyclovir

What Is Acyclovir Used For?

Brand names: Zovirax, Zovirax Injection, Sitavig, Avaclyr

Acyclovir treats infections caused by herpes viruses. Depending on the form, it is used for cold sores (herpes labialis), genital herpes (initial episodes and recurrent flare-ups), shingles (herpes zoster), and chickenpox (varicella). It can also be used long-term to suppress recurrent genital herpes outbreaks.

Some forms are approved for more serious situations: acyclovir injection is used in hospital settings for herpes simplex encephalitis (herpes infection of the brain), neonatal herpes (in newborns), and herpes or shingles infections in immunocompromised patients. Avaclyr ophthalmic ointment is specifically indicated for acute herpetic keratitis (a herpes ulcer on the cornea of the eye). Sitavig buccal tablet and Zovirax cream are specifically indicated for recurrent cold sores in immunocompetent adults.

Most-Reported Side Effects for Acyclovir

From FAERS, the FDA’s public side-effect reporting system (114,761 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Fatigue 8,029 reports
Diarrhea 7,348 reports
Pneumonia 5,700 reports
Nausea 5,643 reports
Fever 4,989 reports
See full Acyclovir drug information
Keep checking

Other Drugs & Bifidobacterium Animalis Subsp. Lactis

Browse every other medication we’ve checked against Bifidobacterium Animalis Subsp. Lactis — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
182Moderate
0Minor
2,647No known interaction
182 Moderate 2,647 No interaction
Moderate

182 interactions

Showing 60 of 182 moderate interactions — see all 182 on the Bifidobacterium Animalis Subsp. Lactis page.

No interaction 2,647 drugs checked — show the list

We also checked Bifidobacterium Animalis Subsp. Lactis against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,647 medications checked with no known interaction — see the full Bifidobacterium Animalis Subsp. Lactis list.

See the full Bifidobacterium Animalis Subsp. Lactis interactions page
See every supplement checked against Acyclovir, ranked by severity
Evidence & sources

Bifidobacterium Animalis Subsp. Lactis References

The 8 references that drive our Bifidobacterium Animalis Subsp. Lactis monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Pierce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York: The Stonesong Press, 1999:19.
  2. Phuapradit P, Varavithya W, Vathanophas K, et al. Reduction of rotavirus infection in children receiving bifidobacteria-supplemented formula. J Med Assoc Thai 1999;82:S43-8.
  3. Xiao JZ, Takahashi S, Odamaki T, et al. Antibiotic susceptibility of bifidobacterial strains distributed in the Japanese market. Biosci Biotechnol Biochem. 2010;74(2):336-42. PubMed
  4. Begtrup LM, de Muckadell OB, Kjeldsen J, Christensen RD, Jarbøl DE. Long-term treatment with probiotics in primary care patients with irritable bowel syndrome--a randomised, double-blind, placebo controlled trial. Scand J Gastroenterol 2013;48(10):1127-35 PubMed
  5. Taipale TJ, Pienihäkkinen K, Isolauri E, Jokela JT, Söderling EM. Bifidobacterium animalis subsp. lactis BB-12 in reducing the risk of infections in early childhood. Pediatr Res. 2016;79(1-1):65-9. PubMed
  6. Amat-Bou M, Garcia-Ribera S, Climent E, et al. Effects of Bifidobacterium animalis Subsp. lactis (BPL1) supplementation in children and adolescents with prader-willi syndrome: A randomized crossover trial. Nutrients. 2020;12(10):3123. PubMed
  7. Mäkelä SM, Forssten SD, Kailajärvi M, et al. Effects of Bifidobacterium animalis ssp. lactis 420 on gastrointestinal inflammation induced by a nonsteroidal anti-inflammatory drug: A randomized, placebo-controlled, double-blind clinical trial. Br J Clin Ph
  8. Wildt S, Munck LK, Vinter-Jensen L, et al. Probiotic treatment of collagenous colitis: a randomized, double-blind, placebo-controlled trial with Lactobacillus acidophilus and Bifidobacterium animalis subsp. Lactis. Inflamm Bowel Dis 2006;12(5):395-401. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Bifidobacterium Animalis Subsp. Lactis and Acyclovir Together: Common Questions

Is it safe to take Bifidobacterium Animalis Subsp. Lactis with Acyclovir?
We do not list a known interaction between Bifidobacterium Animalis Subsp. Lactis and Acyclovir. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Bifidobacterium Animalis Subsp. Lactis and Acyclovir have any of the same side effects?
Yes — our sources link each of them separately to 3 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How was the Bifidobacterium Animalis Subsp. Lactis and Acyclovir combination checked?
Interactions in our licensed database are recorded against drug classes. Acyclovir is filed under 6 classifications, and Bifidobacterium Animalis Subsp. Lactis has documented interactions with 1 drug class — none of Acyclovir's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Bifidobacterium Animalis Subsp. Lactis interact with any other medications?
Yes. Bifidobacterium Animalis Subsp. Lactis has 182 documented drug interactions in our database — Acyclovir is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Acyclovir interact with any supplements?
Yes. Acyclovir has documented interactions with 37 supplements in our database — Bifidobacterium Animalis Subsp. Lactis is not one of them. The Acyclovir interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Where next

Keep Exploring

Bifidobacterium Animalis Subsp. Lactis monograph Uses, safety profile, and every drug interaction in one place Acyclovir drug information The full plain-English guide to this medication Acyclovir supplement interactions Every supplement checked against Acyclovir, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 8 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Acyclovir and Bifidobacterium Animalis Subsp. Lactis?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.