Probiotics for Acute Otitis Media

Not reliably. Pooled trials show a small drop in ear infections, but only in children not prone to them, and the two largest recent trials found none. In detail, for acute otitis media in children, a 2019 Cochrane review of 17 randomised trials in 3,488 children found that probiotics lowered the share of children with an ear infection (RR 0.77, 95% CI 0.63 to 0.93; 16 trials, 2,961 children; moderate-certainty evidence; number needed to treat about 10). The benefit appeared only in children not prone to ear infections (RR 0.64, 95% CI 0.49 to 0.84), in a post hoc subgroup analysis. Among otitis-prone children the review found no difference (RR 0.97, 95% CI 0.85 to 1.11; high-certainty evidence), and the subgroup difference was significant (P = 0.007).

Two larger trials in general populations have since been published. In 827 Finnish day care children, daily Streptococcus salivarius K12 for 6 months did not help: antibiotic-treated ear infections occurred in 8.2% of children on K12 versus 5.8% on placebo (RR 1.42, 95% CI 0.86 to 2.34; not a significant difference). In 428 New Zealand infants given K12 from 6 to 24 months, doctor-recorded ear infections occurred in 37% versus 39% on placebo (rate ratio 0.84, 95% CI 0.57 to 1.24). The 2019 Italian Society of Pediatrics guideline does not recommend probiotics, and none of the trials in the Cochrane review reported how severe infections were. The 2026 New Zealand trial did measure severity and found no difference.

Several trials tried to change the bacteria living in a child's nose and throat. Children with recurrent ear infections were found to have fewer alpha-haemolytic streptococci in the nasopharynx than healthy children, and the ones they did have inhibited the common ear-infection bacteria less well in the laboratory. That led to nasal sprays of streptococci chosen for their ability to inhibit those bacteria.

Individual strains were picked for their laboratory activity. S. salivarius 24SMB produces bacteriocin-like substances (proteins that inhibit other bacteria) with activity against ear-infection bacteria, Lactobacillus salivarius PS7 was selected for strong antimicrobial activity against them, and S. salivarius K12 has shown antimicrobial and immunomodulatory activity in vitro.

Laboratory activity has not reliably become clinical benefit. In 309 otitis-prone children, a four-strain capsule left carriage of Streptococcus pneumoniae and Haemophilus influenzae unchanged and raised carriage of Moraxella catarrhalis, another ear-infection bacterium (OR 1.79, 95% CI 1.06 to 3.00). In a nasal-spray trial of 43 children the nasopharyngeal flora did not change significantly. In a 24SMB trial, the strongest result compared treated children who became colonised with those who did not, a split made after treatment.

The largest K12 trials found no reduction in ear infections. The mechanism is a reason to run trials, not a reason to expect them to be positive.

There is no established dose. The Cochrane review found that the strains tested, and their dose, frequency and duration, varied considerably, and said the optimal ones still need to be established. The largest trial used 1 billion CFU (colony-forming units, a count of live bacteria) of S. salivarius K12 daily for 6 months, as a powder sachet under age 3 or a chewable tablet from age 3. A pilot of L. salivarius PS7 used about 100 million CFU daily.

Nasal-spray trials used much shorter courses: 24SMB twice daily for 5 days each month for 3 months, or a streptococcal spray for 10 days after antibiotics, repeated from day 60. The table shows what was tested and what happened, not what to take.

The 2019 Cochrane review is the main pooled evidence for probiotics. It included 17 randomised trials in 3,488 children (mean age 2.4 years); 11 tested Lactobacillus-containing products and six tested Streptococcus-containing ones. Probiotics lowered the share of children with an ear infection (RR 0.77), the share taking antibiotics for any infection (RR 0.66, 95% CI 0.51 to 0.86; 8 trials, 1,768 children) and the share with other infections (RR 0.75, 95% CI 0.65 to 0.87). School days lost did not differ (mean difference -0.95 days, 95% CI -2.47 to 0.57).

The pooled benefit sits entirely in a post hoc subgroup of children not prone to ear infections (RR 0.64; 11 trials, 2,227 children); in otitis-prone children there was none (RR 0.97; 5 trials, 734 children; high certainty). The review's own authors said the inconsistency of the subgroup analyses suggests caution, and noted heterogeneity from the varied strains and doses.

The newest and largest trials are null. The Finnish K12 trial (827 children, 50 day care centres) found antibiotic-treated ear infections in 34 children on K12 and 24 on placebo (RR 1.42, 95% CI 0.86 to 2.34; P = .17). The New Zealand trial (428 infants randomised by household, 368 with outcome data) found a rate ratio of 0.84 (95% CI 0.57 to 1.24), and its authors concluded routine use in general paediatric populations is not supported.

Older trials agree. A 24-week trial of a four-strain capsule in 309 otitis-prone children found ear infections in 72% on probiotics and 65% on placebo (OR 1.48, 95% CI 0.87 to 2.52). A 12-month French trial of a probiotic and prebiotic formula in 224 high-risk infants found 249 versus 237 episodes (incidence rate ratio 1.0). A nasal spray of alpha-haemolytic streptococci in 43 children with recurrent infections gave 7 versus 8 recurrences.

A trial of 72 formula-fed infants given Lactobacillus rhamnosus GG and Bifidobacterium lactis Bb-12 found ear infections before 7 months in 22% versus 50% on placebo (RR 0.44, 95% CI 0.21 to 0.90), but ear infection was one of several infection outcomes, and the authors called for further trials. A 2001 trial of a nasal streptococcal spray after antibiotics found 42% of children healthy with a normal eardrum at 3 months versus 22% on placebo, but followed them for only 3 months, and a later small trial of a similar spray found no effect.

In 100 otitis-prone children, S. salivarius 24SMB nasal spray gave 30.0% free of ear infections versus 14.9% on placebo, which was not significant (P = 0.076); the significant result compared colonised and non-colonised treated children. A pilot of L. salivarius PS7 reported 84% fewer episodes in 61 children, but with no control group, so the fall cannot be separated from natural variation.

A 2025 meta-analysis of 16 trials (4,034 patients) mixing probiotics, prebiotics and synbiotics found a lower chance of an ear infection (RR 0.80, 95% CI 0.66 to 0.96) but no effect on time to infection, recurrence (RR 0.99) or antibiotic need (RR 1.31, 95% CI 0.92 to 1.84). A 2020 systematic review of 13 studies of poor to moderate quality concluded the evidence is limited, with nasal formulations positive in two of four studies and oral ones in three of nine. A 2026 network meta-analysis of 18 trials (4,462 children) found only CBA-L74 and K12 reduced ear infections versus placebo, and K12's effect lost significance after two high risk-of-bias trials were excluded.

Missing from the record are an independent replication of the nasal-spray results, head-to-head strain comparisons, and any trial that tested starting a probiotic after an infection had begun. For other supplements studied for the same question, see xylitol and vitamin D; the Italian guideline does not recommend any of the three.

In the trials, probiotics were generally tolerated. The Cochrane review found adverse events did not differ between probiotic and comparison groups (OR 1.54, 95% CI 0.60 to 3.94), but that came from four trials in 395 children and the certainty was low, so a harm cannot be ruled out. A 2020 systematic review found no significant adverse effects, and in the French formula trial both formulas were well tolerated for gastrointestinal problems.

The US National Center for Complementary and Integrative Health notes that probiotics usually have few side effects, but safety data, especially long-term, are limited, and the risk of serious side effects may be greater in people with underlying health conditions. In one trial, a four-strain capsule increased carriage of Moraxella catarrhalis, an ear-infection bacterium, although ear infections were not significantly more frequent on probiotics.

Product quality is a separate risk. Probiotic supplements do not need FDA approval before they are sold, and some products have been reported to contain microorganisms not listed on the label, which in some instances may pose serious health risks (NCCIH). The FDA notes that unapproved probiotics sold for infants have not been tested for extraneous organisms. Possible harms of probiotics include infections, harmful substances made by the organisms and transfer of antibiotic resistance genes.

The trials and guidelines reviewed here report no specific drug interactions. The practical risks are substitution and special groups: a probiotic has not been shown to treat an infection, and it should never delay seeing a clinician for ear pain, fever or ear discharge.