Less than 1% of Americans are allergic to penicillin, though about 10% of Americans believe they have this allergy.

Most penicillin allergy diagnoses are wrong, leading to costlier, less effective treatments and contributing to the growing problem of antibiotic resistance.

Penicillin is considered one of history’s greatest medical breakthroughs

Experts widely rank penicillin’s discovery among the most important advances in medicine. It launched the antibiotic era, transformed once-deadly infections into treatable illnesses.

Penicillin was hailed as a 'wonder drug' upon its release

When penicillin became widely available in the 1940s, newspapers and doctors alike celebrated it as a “wonder drug” that could cure infections once considered fatal.

Amish kids have far fewer allergies than the general population

Only about 7% of Amish children in a northern Indiana community have tested positive for common allergens in routine skin prick tests, whereas half of the general US population tests positive for them. Asthma is also extremely uncommon among the Amish, even when compared with other farming communities. Researchers are interested in exploring if approaches like exposing kids across the general population to Amish farm dust might stave off some allergies.

Penicillin has saved an estimated 500 million lives since its creation

Since its introduction in the 1940s, penicillin and related antibiotics are estimated to have saved around 500 million lives worldwide—making it one of the most consequential medical breakthroughs in human history.

It took 14 years to deploy penicillin after its discovery

Despite its promise, US production of penicillin remained minimal in 1942—enough to treat fewer than 100 patients nationwide. Within two years, output expanded into millions of doses to supply troops for D-Day.

Penicillin ended scarlet fever’s deadly threat to children

Between 1840 and 1883, scarlet fever was among the leading causes of childhood death in the United States, with case fatality rates ranging from 15% to 30%. Today, thanks to antibiotics like penicillin, the mortality rate is below 1%.

Penicillin was discovered by accident

In 1928, Alexander Fleming returned from vacation to find mold contaminating a petri dish of bacteria. Around the mold, the microbes had died—an accidental observation that led to the discovery of penicillin.

Allergy tests identify antibodies, but not whether allergy symptoms may appear

Skin prick tests and blood tests, the two most common allergy tests, both detect the presence of allergen-specific antibodies. But just because the body has those antibodies doesn’t mean that a person is “allergic” to a substance or that they will develop symptoms of an allergy when encountering the substance. Allergists work with families to interpret the results and sometimes combine that data with approaches including exposure challenges—giving someone a tiny bit of the food or substance they may be allergic to—under medical supervision.

More than 90% of America's food allergies are triggered by 9 foods.

Penicillin slashed battlefield pneumonia deaths during World War II

Before antibiotics, bacterial pneumonia killed about 18% of infected soldiers in World War I. By World War II, penicillin cut that death rate to less than 1%.

The word allergy is partly derived from the Greek word 'allos' for 'other'

For people with allergies, their immune systems recognize substances as a harmful "other"—cuing an inflammatory response. This podcast explores allergy details and related topics, including how scientists are interested in if the same allergic response mechanisms could underpin other health issues, including severe, painful symptoms around the time of menstrual cycles. Since estrogen acts on white blood cells called mast cells, which leads to the release of histamines—similar to what happens during allergic responses—an understudied question is whether the same process is fueling some of the uncomfortable symptoms around menstruation. An allergist guest notes this raises questions about if antihistamine medications like Pepsid might alleviate them, something that hasn't yet been explored in clinical trials.

Penicillin production was just behind the atom bomb in wartime priorities

By 1943, the US War Department made penicillin its second-highest priority—just after the Manhattan Project. Producing enough of the antibiotic for the D-Day invasion became a central mission of Allied science and industry.

Penicillin’s discoverer predicted antibiotic resistance

Alexander Fleming’s discovery of penicillin revolutionized modern medicine. But the same man who pioneered the development of antibiotics also recognized that bacteria could make sntibiotics obsolete if they were used irresponsibly. This story sheds light on Fleming’s discovery—and on his prophetic warning about antibiotic resistance.

Pneumonia was once a leading killer before penicillin treatments

In the early 20th century, pneumonia was a top cause of death worldwide, often fatal without effective treatment. Penicillin turned a once deadly infection into one of the most treatable bacterial diseases.

Peanut allergies dropped by 43% after doctors reversed avoidance guidance, but questions remain

The study’s data appear to confirm the policy shift. Still, since the study did not include an examination of infant diet, researchers can’t definitively say that the guideline shift led to dietary changes and thus directly caused the decline.

Adults are developing food allergies that they didn’t have as children

Research published in 2019 found that almost half of 40,000 surveyed adults with food allergies developed a new food allergy as adults, underscoring that our immune systems may newly misclassify substances later in life.

Unlike food allergens, encountering inhaled allergens—like pollen—rarely causes life-threatening illness.

Penicillin supplies were ready for every wounded soldier on D-Day

By June 1944, Allied stockpiles included 2.3 million doses of penicillin—enough to ensure that every soldier wounded during the pivotal Normandy landings could receive treatment.

Home allergy tests don’t work well and experts urge caution

Doctors do not recommend at-home allergy test kits because their results may be inaccurate and confusing, and lead people to make lifestyle changes that are not warranted. Tests that require sending in a hair sample, for example, will not be helpful because hair does not have the relevant antibodies that blood testing would detect.

The science of food allergies

Why do certain substances trigger an immune response while others don't? Listen to researchers explain the science in this five-minute video. Food allergies affect around 8% of children and 2% of adults in the US, and—unlike sensitivity or intolerance—they involve the immune system mistaking certain harmless proteins in foods as dangerous invaders, triggering a rapid and sometimes severe defense response.

Penicillin works by attacking the cell walls of bacteria

Penicillin targets bacteria at their weakest point—their cell walls. By blocking wall-building, it leaves microbes unable to survive, causing them to burst and die.

One-third of kids with food allergies report being bullied because of it, surprising parents

Research published in 2021 surveyed how more than 100 kids with food allergies were treated by their peers. About one-third of the surveyed kids had their allergies used against them. Bullying tactics included that their allergens were sometimes intentionally put in their food or thrown at them. Parents usually had no idea this bullying was happening.

86 commonly used drugs, including certain antidepressants, painkillers, and immunosuppressants, have different results for men and women, according to recent research.

FDA approved the first ever peanut allergy treatment in January 2020

This new medication, called Palforzia, is designed to stave off severe reactions from accidental peanut exposures with a daily dose that is increased over time under an allergist’s supervision. It’s not a treatment that should be administered during an allergic reaction, however. Epinephrine, usually administered via injection, remains the intervention for severe reactions.

Gut microbiome rewrites may help reduce allergies

Researchers are investigating different strategies to determine if one day they could give people a combination of gut microbes to set them up for fewer allergies. In animal research, scientists have already prevented severe allergic responses in allergy-prone mice—supplying them with gut microbes from healthy, non-allergic human babies.

Penicillin’s pioneers were awarded the Nobel Prize in 1945

Alexander Fleming, Howard Florey, and Ernst Chain received the 1945 Nobel Prize in Physiology or Medicine for discovering and developing penicillin.

Why some people have allergies

Why do some people have allergies while others don’t? One theory suggests allergies are a relic of our evolutionary past. Our immune system, once primed to fight parasites, now mistakes harmless substances for threats.

Researchers are investigating if nanoparticle treatments could combat allergies

In rodent work, Northwestern University’s Evan Scott (now at the University of Virginia) and his colleagues have been trying to attack allergies with specially designed nanoparticles—miniscule lab-made objects that can penetrate cells. They stud the nanoparticles with a tiny bit of the allergen specific to the allergy (i.e. cashew protein for cashew allergy) and antibodies that shut down allergic response processes.

Inhalers, antihistamines, immunotherapy, and more have made allergies a multimillion-dollar market

Market research suggests that the allergies market will continue to grow in the years ahead as the number of allergy diagnoses increases, identifying new patients. Areas of growth include the increasing interest in immunotherapies designed to retrain the immune system through regular exposure to potential allergens via injections and under-the-tongue medical formulations, among other approaches.

Scientists are using CRISPR to genetically modify felines so they don't trigger allergies in humans.

Kids often grow out of allergies to milk and eggs

Between 60% and 80% of kids with allergies to milk or eggs outgrow them by age 16. The immune system doesn’t always recognize and respond to baked forms of these allergens, so when kids eat muffins and other cooked food products, their immune system may become more habituated to them and overcome food sensitivities. Aging out of other allergies is less common.

The same mold behind penicillin also flavors blue cheese

There are over 300 species of Penicillium. The mold that produces the lifesaving antibiotic is a close relative to those used to make blue cheeses like Roquefort and Stilton and to flavor some types of ham.

More than 1 in 7 people worldwide have had Lyme disease

Research published in 2022 suggests that 14.5% of the world's population has contracted Lyme disease. Researchers arrived at that estimate by analyzing the presence of Lyme disease antibodies (indicating prior infection) across 89 studies conducted between January 1984 and December 2021. The works collectively included blood samples from more than 150,000 people. (Some user may encounter a paywall.)

The 'Penicillin Girls' made mass production possible

In Oxford during the early 1940s, six female technicians—later dubbed the “Penicillin Girls”—worked long hours tending mold cultures and extracting tiny amounts of penicillin.

Tips for reducing the risk of antimicrobial resistance

Antimicrobial resistance is bad news. But there are lots of things you can do to both protect yourself from superbugs and help keep the problem of antimicrobial resistance from getting worse. This page from the CDC offers clear, straightforward guidelines that can help keep you—and your loved ones—healthy.

Allergies occur when our immune system mistakenly considers a substance a threat

Immunoglobulin E antibodies, or IgE antibodies, may bind to an allergen, effectively labeling it as a threat. That triggers a cascade of actions in the body, including the release of histamine, which causes the characteristic itching and hives of allergies. Sometimes a cooked version of an allergen—like a cooked carrot—may look different enough from its raw form to the immune system that antibodies ignore it, and no allergic response takes place.

Knowing how to use an EpiPen is a life-saving skill—learn how with this video

If someone has a severe allergic response, including trouble breathing or two or more allergic symptoms, it may be necessary to administer epinephrine, usually through an injection. Epinephrine autoinjectors—often called EpiPens—should be injected into the mid-outer thigh, even through clothing, for about 10 seconds, depending on brand. Sometimes another injection with a separate EpiPen is required if the patient does not get better after a few minutes.

Overuse of antibiotics gives bacteria more opportunity to evolve their defenses

The overuse and misuse of antibiotics are significant contributors to the rise of antibiotic resistant bacteria. Experts say antibiotics should only be used for specific medical problems, and patients need to be sure to take antibiotics exactly as prescribed in order to reduce the risk of antibiotic resistance.

Modern conveniences may be contributing to allergy increases

A combination of genetics and how the environment changes our genes are likely contributing to the rise in allergies. But daily conveniences, such as dishwashers and packaged baby food, also change the level of bacterial exposures in early life, with potential implications for allergy development, experts from Mount Sinai Health System state in this video discussion.

CRISPR technology is removing allergens from common foods

Proteins responsible for allergies to eggs, milk, wheat, peanuts, and other foods can be genetically edited out of foods to reduce the risk of life-threatening reactions. The technique has also been used to produce caffeine-free coffee beans, spicier tomatoes, allergen-free pets, and more nutritious fish.

A moldy cantaloupe supercharged penicillin production

In 1943, a moldy cantaloupe found at a market in Peoria, Illinois, yielded a strain that produced six times more penicillin. Though often credited to lab worker “Moldy Mary” Hunt, accounts differ on who actually brought in the fruit.

Genetic drug matching, called pharmacogenomics, can help avoid dangerous drug reactions

Certain gene variants can affect how quickly or slowly medications are broken down in the body, affecting drug effectiveness and the risk of drugs failing. Such testing is often not covered by insurance companies though research indicates if these tests were performed for more than six drugs across the US population, avoided ailments would likely climb into the hundreds of thousands. (Some users may encounter a paywall.)

Embracing poor hygiene in early life won't stave off allergies

The hygiene hypothesis, first proposed in 1989 by British immunologist David Strachan, suggests that early life exposure to microbes—like those from farm dust or pets—properly trains our immune systems to respond to threats. But sometimes the idea is misinterpreted: It doesn’t mean that poor hygiene—like failing to wash hands–will help ward off allergies; that type of behavior leads to infections and won’t help with allergy prevention.

Antibiotic resistance is a growing global health problem

Over decades, bacteria have grown increasingly resistant to antibiotics. This resistance now causes an estimated 1.27 million deaths each year and is associated with nearly 5 million deaths worldwide, according to the World Health Organization.

Diphtheria was once a leading childhood killer before antibiotics and vaccines

In 18th- and 19th-century outbreaks, some New England families lost as many as eight children to diphtheria, and fatality rates in hospitals often topped 60%. The invention of antitoxins, penicillin, and vaccines dramatically reduced deaths.

Most of the 86,000 consumer chemicals registered with the US EPA have never received rigorous toxicity testing, though not all those are still in current use.

About 95% of people are naturally immune to leprosy.

Alpha-gal allergy is a problem for red meat lovers, and that same alpha-gal sugar is an issue for xenotransplants, too—since it's present in pigs, human bodies reject pig-to-human transplants as foreign once they detect the substance.

Blood tests for Lyme disease tend to come up as false negatives in the week after a bite

It can take several weeks for Lyme antibodies to develop, which is what blood tests would be detecting. That's why many clinicians will prescribe antibiotic treatment immediately after a bite if the individual develops the characteristic bullseye rash of Lyme or gets bitten in an area of the country known to have high rates of Lyme.