In short
Lactobacillus rhamnosus GG (LGG) is a probiotic bacterium authorised as a medicine in Germany for young children. It is being studied as a test treatment in one Phase 2 trial with 96 participants to see whether it can reduce symptoms of pollen-associated food allergy when given alongside sublingual birch immunotherapy.
Key points
- Lactobacillus rhamnosus GG is a probiotic bacterium authorised as a medicine in Germany for infants and young children.
- One Phase 2 trial is studying LGG in pollen-associated food allergy together with birch immunotherapy.
- The trial plans to enrol 96 participants and is currently authorised.
- The main measure is change in a combined visual analogue scale for itching, stinging and prickling after an apple challenge.
- LGG is given as an oral suspension for use in the mouth in the trial.
- Probiotics may carry a rare risk of infection in people with weakened immune systems.
What is lactobacillus rhamnosus GG?
Lactobacillus rhamnosus GG, also called LGG, is a probiotic bacterium. It belongs to the group of lactic acid producing organisms and is classified under the ATC code A07FA01. LGG is a structurally diverse substance of biological origin, not a chemically synthesised drug. In Germany it is authorised as a medicine under the product name INFECTODIARRSTOP® LGG® Mono, supplied by INFECTOPHARM Arzneimittel und Consilium GmbH. The authorised product is a powder for making an oral suspension for infants and young children, containing freeze-dried LGG at a strength of at least 5 x 10⁹ colony-forming units. A paediatric formulation exists for this product.
How does lactobacillus rhamnosus GG work?
LGG is a probiotic, meaning it is a live microorganism intended to have a beneficial effect on the host. Research on LGG has focused on how it interacts with the human body, particularly the surfaces of the gut and the immune system. The exact way LGG might influence allergic responses is still being investigated. In the registered trial, LGG is not used alone but is tested together with a sublingual birch immunotherapy called ITULAZAX.
Which conditions is lactobacillus rhamnosus GG used or studied for?
- Pollen-associated food allergy — an allergic condition in which a person reacts to certain foods because of cross-reactivity with pollen allergens. The trial studies whether LGG can help reduce these food allergy symptoms during an apple challenge.
- Birch pollen allergy — an allergy to birch pollen that can be linked to reactions to foods such as apple. This is the underlying allergy being treated in the trial with birch immunotherapy.
How is lactobacillus rhamnosus GG given?
LGG is prepared as an oral suspension and is given by oromucosal use, meaning it is applied in the mouth. In the trial, the LGG product is a powder for making a suspension, with each dose containing at least 5 x 10⁹ colony-forming units of freeze-dried LGG.
What do the clinical trials show?
One Phase 2 interventional trial is registered for LGG in pollen-associated food allergy. The trial, with the EU CT number 2025-523653-34-00, is authorised and plans to enrol 96 participants. It tests whether a short course of sublingual immunotherapy with ITULAZAX plus LGG is superior to placebo in reducing pollen-associated food allergy symptoms. The main outcome is the change from baseline to Visit 5 in a combined global visual analogue scale measuring itching, stinging and prickling within five minutes after a standardised apple challenge. The trial also includes a placebo comparison arm.
What side effects are known?
Probiotics such as LGG are generally considered safe, with minimal to low pathogenicity. However, serious infections including bacteremia and endocarditis with lactobacilli have been rarely reported, mainly in critically ill people or those with significant underlying conditions such as cancer, organ transplantation, AIDS, valvular heart disease, diabetes mellitus, recent surgery or a compromised immune system. Lactobacillus pneumonia and liver abscess have also been described in the medical literature.
Are there any drug interactions?
Using probiotics during immunosuppressant or intensive antineoplastic therapy may theoretically increase the risk of infections from the live microorganisms in probiotic products. Caution is advised when probiotics are used during such therapy, and it may be advisable to avoid them in people who are significantly immunosuppressed unless the expected benefits outweigh the potential risk of infection.