Protocols › Probiotics

Probiotics for colds

Goal: What trials used to lower the number and length of colds and other upper airway infections.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 4 Nov 2026
Dose

Most trials used 1 billion or 100 billion colony-forming units (CFU, live cells) a day.[1]

Form

One or two strains in most trials, such as Lactobacillus plantarum HEAL9 or Lactobacillus paracasei 8700:2 or N1115. Children mostly got them in milk-based food, adults as a powder, and older people in milk-based food or capsules.[1]

How long

More than 3 months in most trials.[1]

What studies found

23 trials with 6950 people. 24% fewer people had at least one infection (low certainty), infections were 1.22 days shorter (low certainty), and 42% fewer people needed antibiotics for them (moderate certainty).[1] These results come from the strains tested.[1]

Ask a doctor first

Side effects were minor and mostly affected the gut, such as vomiting, gas, diarrhea and bowel pain.[1] Probiotics have been linked to rare blood infections, mostly in people who were severely ill or had a weak immune system.[2]

People with a weak immune system or a serious illness should ask a doctor or pharmacist first.[2]

References

  1. Probiotics for preventing acute upper respiratory tract infections. Zhao Y, Dong BR, Hao Q Cochrane Database Syst Rev, 2022. PMID 36001877
  2. Probiotics: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2025. ods.od.nih.gov