Life Extension Magazine®

Scientist examining Lactobacillus rhamnosus and its immune effects

Enhanced Immunity Against Allergies and Colds

Scientists have identified a probiotic and yeast fermentate combination that reduced the frequency of colds and flus by 55%.

Scientifically reviewed by: Dr. Gary Gonzalez, MD, in August 2023. Written by: Michael Downey.

Allergies and colds affect people of various age groups.

Drugs target symptoms without correcting under-lying causes of these miseries.

Scientists have discovered two ingredients that reduce the severity of allergy and cold symptoms and help prevent them from occurring.

Human studies show that these ingredients lead to:1-3

  • 55% decreased cold and flu occurrence,
  • 43% fewer days with nasal congestion,
  • 17% reduced duration of cold and flu-like symptoms, and
  • 47% increased salivary immunoglobulin A, an antibody that provides immune defense against viruses and bacteria.

This article describes how one may reduce frequency and duration of allergy and cold symptoms.

Colds, Allergies, and Other Infections


American adults get an average of two to three colds annually,4 and as many as 30% of U.S. adults suffer from allergies.5

Sometimes it feels like we spend half our lives sneezing, coughing, and blowing our noses. This has a major impact on quality of life, but there’s a more serious danger: Allergies have been associated with other conditions, such as asthma, and sinus and ear infections.6,7

Preventing and Reducing Symptoms

Medications provide mild relief of symptoms but do nothing to reduce the number of colds and allergy bouts per year or how long they last.

Side effects from these drugs can include drowsiness, constipation, headaches, rapid heartbeat, and sleep problems.8 One class of allergy drugs, anti-cholinergics, has even been linked to an increased risk of Alzheimer’s disease.9

Scientists have identified two ingredients that help prevent colds, flu, and allergic episodes, and lessen the severity and duration of symptoms when they do occur.1-3

The ingredients are:

  • A dried yeast fermentate and
  • A probiotic called Lactobacillus rhamnosus CRL1505.

Each of these ingredients boosts activity of immunoglobulin A (IgA), an antibody that provides immune defense against viruses and bacteria.3,10

Discovery of Yeast’s Immune Benefits

The immune effects of yeast fermentate were discovered by accident.

A company in Cedar Rapids, Iowa, had been producing a specialized yeast culture when it became apparent that its factory workers—who were exposed to the yeast daily through inhalation—were taking far fewer sick days than its office workers.

Scientists took note. A pilot study showed that, compared to the office staff, the factory personnel had significantly higher levels of secretory IgA, an antibody that blocks pathogens from penetrating mucosal surfaces.11

They also had increased activity of natural killer cells, immune cells that can kill cells infected with viruses.12

The company went on to develop the dried yeast fermentate using a proprietary fermentation process and baker’s yeast. At least six placebo-controlled clinical trials have since validated its protection against allergies and colds.1,2,10,13-15

Defense Against Allergies


Scientists first conducted a small pilot study on 25 healthy individuals, giving them either a placebo or 500 mg of dried yeast fermentate daily for five weeks during the beginning of allergy season.10

Seasonal allergies did not change in the placebo group.

In the group taking the yeast fermentate there were improvements. Half of the treated male volunteers reported a complete absence of allergy symptoms, which returned within two weeks once they stopped taking the yeast fermentate.10

Researchers then conducted a clinical study on 96 volunteers with a history of seasonal allergies and hay fever. Participants took either a placebo or 500 mg of dried yeast fermentate once daily.1

The first six weeks of the 12-week study took place during the year’s highest pollen-count period. Compared to the placebo group, those taking yeast had 43% fewer days with nasal congestion. They also had a reduction in the severity of runny noses and nasal congestion.

By the study’s end, those taking yeast fermentate showed decreased levels of white blood cells in their nasal mucus, indicating reduced activation of allergy-triggering cells.1

Yeast Fermentate Fights Colds and Flu

Scientists next set up two clinical studies to examine yeast fermentate’s effect on cold and flu-like symptoms.

In the first, they gave a daily dose of 500 mg of dried yeast fermentate to 116 people with a mean age of 37. The 12-week trial was conducted from January through March, during the height of cold and flu season.

At the end of the study, the yeast group had experienced a 13% reduction in the occurrence of cold or flu-like symptoms (including headache, fever, general aches and pains, fatigue, nasal stuffiness, sore throat, cough, and chills) compared to the placebo group.14

The second study was virtually identical to the first, except that the 116 participants had an average age of 44. They received the same dosages of the dried yeast fermentate or a placebo and recorded the incidence and duration of symptoms.2

Compared to the placebo group, the yeast-treated group had 11% fewer incidences of common cold or flu-like symptoms, and a 17% reduction in the duration of symptoms.

What you need to know

Defending Against Allergies, Colds, and Infections Year-Round

  • Clinical studies show that a yeast fermentate and the probiotic Lactobacillus rhamnosus CRL1505 decrease the frequency, duration, and severity of allergy and cold symptoms.
  • These ingredients also boost natural killer cell activity and immunoglobulin A (IgA) immune defenses against viruses and bacteria.
  • Combining these two ingredients provides a safe and effective way for cold, flu, and allergy sufferers to improve their quality of life and may reduce risk of infection.

How Yeast Fermentate Works


Antibodies called immunoglobulin E (IgE) are a main cause of allergy symptoms. IgE causes the body to release chemicals, such as histamines, that trigger an allergic reaction and produce symptoms that affect the eyes, nose, throat, lungs, or skin.

In the small pilot study that first showed yeast fermentate’s ability to relieve allergy symptoms, blood levels of IgE steadily increased among placebo recipients as allergy season went into full swing, indicating heightened allergic responses.

In subjects taking the yeast, IgE levels barely changed, indicating a reduced allergic reaction.

The study concluded that yeast fermentate calms allergic responses by stabilizing IgE levels.10

Yeast’s ability to help prevent colds and flu comes from a different property. When given a single dose of 500 mg of dried yeast fermentate, volunteers had significantlyincreased activity of natural killer cells within just one hour.13 These immune cells specifically target and kill cells infected by viruses, such as those that cause colds and flu.

Healthy individuals given 500 mg of yeast fermentate daily also had a significant increase in salivary IgA, which defends against viruses and bacteria, after eight weeks.10

A Probiotic’s Cold and Flu Defense


Probiotics are beneficial live microorganisms. A specific strain of probiotic, the bacterium Lactobacillus rhamnosus CRL1505, was originally isolated from goat’s milk by scientists in northwestern Argentina.16

A series of studies showed that it decreased respiratory infections in children. Results were so impressive, the government of Argentina has been proactively providing L. rhamnosus CRL1505 to over 300,000 school children annually since 2008.3,16,17

Preclinical studies show that this probiotic strain may help fight the viruses and bacteria that cause the common cold, influenza, bronchitis, and pneumonia.17,18

A team of nutritionists, pediatricians, and immunologists designed a randomized, double-blind, placebo-controlled clinical trial. They enlisted 298 healthy male and female children between two and five years of age.3 This population is particularly susceptible to respiratory infections.

Five days a week, the treatment group was given100 million CFU (colony-forming units) of L. rhamnosus CRL1505 in a yogurt drink. The placebo group received a drink without the probiotic.

After six months, when compared to the placebo group, the children in the probiotic group had experienced:3

  • 49% fewer infections,
  • 55% fewer cases of cold or flu,
  • 46% fewer cases of fever,
  • 47% increase in levels of salivary IgA, and
  • 33% less need for antibiotic use.

The treatment group also had 61% fewer cases of tonsillitis and pharyngitis, an infection in the back of the throat.3

How the Probiotic Works

IgA antibodies are a major part of the immune system. Secreted from mucous membranes in the mouth, nose, and lungs, they bind to respiratory viruses, blocking them from invading human cells and producing symptoms of colds and flu.

Research shows that L. rhamnosus CRL1505 significantly increases levels of secretory IgA, 3 boosting the immune system’s initial ability to fight cold and flu viruses.

Along with yeast fermentate, this probiotic has demonstrated a reduction in severity, frequency, and duration of cold and flu symptoms and may offer protection against infections.



Allergies and colds are more than an inconvenience.

Human studies show that a yeast fermentate and the probiotic Lactobacillus rhamnosus CRL1505 reduce the severity, occurrence, and duration of allergy, cold, and flu-like symptoms.

These two ingredients work in multiple ways to enhance immune defenses against viruses and bacteria.

If you have any questions on the scientific content of this article, please call a Life Extension ® Wellness Specialist at 1-866-864-3027.


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