Table of Contents:
- Antibiotics
- Vaccination
- Microbes
- Sanitize
Are antibiotics more harmful when given earlier in life?
Yes. In a study published in the British Medical Journal, antibiotic exposure early in life was associated with a higher chance of asthma. Antibiotics given later in life did not have the same effect. When a child’s gut bacteria are changed matters as much as whether they are.
If someone asked whether babies and germs should mix, you would probably say no by reflex. These two life forms are not exactly meant to go hand in hand, at least in the usual sense. Yet this is the very idea the book “Let Them Eat Dirt: Saving Your Child from an Oversanitized World” sets out to challenge. Doctors Brett Finlay and Marie-Claire Arrieta wrote it. The book takes a controversial stand against keeping a baby’s world too clean.
Until recently, the rule was that a baby’s world should be as clean as possible. In the book’s words, the belief was “the only good microbe is a dead one.” There is no denying that we are here today thanks to medical milestones. Each aimed to control microbes. They include vaccines, sterilization, pasteurization of food, and antibiotics. Still, we now face a new wave of autoimmune diseases. It is clearer that this old, time-tested plan might not work anymore.
The authors point to a pattern. Countries that tend to over-clean have significantly higher rates of non-infectious diseases (diseases that are not infections). These include asthma, diabetes, and autoimmune conditions. Meanwhile, people who live around a richer mix of microbes tend to report lower numbers of these diseases.
To back this up, the authors pointed to an article Dr. David Strachan published almost 25 years earlier. In it, Dr. Strachan said that a lack of contact with bacteria in early childhood helped cause allergies. He also said that without contact with bacteria, our immune system will not fully mature. These ideas later became known as the hygiene hypothesis.
New studies have come out that support the hygiene hypothesis. So the authors listed the possible culprits that hold back the growth of the immune system.
One culprit is the misuse of antibiotics. The book stresses that antibiotics truly save lives. In the past, 90 percent of children would eventually die from bacterial meningitis. Now a full recovery is the standard. Sadly, the world is overusing antibiotics. One estimate says that between 2000 and 2010, antibiotic use rose by 36 percent worldwide. Even more alarming, use goes up during flu season. At that time the drugs are almost useless, because influenza is caused by viruses that do not respond to antibiotics. The real harm is not that they are useless. It is the damage they do to the normal flora (the healthy bacteria that live in the body).
Even if we use antibiotics properly for the right reasons, there is still the problem of antibiotics in our food. Livestock are widely given antibiotics as supplements, which increases the meat yield. Europe has banned this practice, but it is still in use in the United States. Antibiotics seem to have a similar growth effect in children as they do in animals. According to the CDC, the states with the highest antibiotic use also have higher rates associated with obesity.
At first, this was just a matter of statistics. But after the finding was repeated in the lab, the concern is clearly valid. When mice with sterile guts were given bacteria from obese mice, the test mice became obese too. This further supports the idea that the mix of gut bacteria affects weight gain.
The effect does not stop at weight. It would appear that even allergies are deeply rooted in how the bacterial flora is set up. A study in the British Medical Journal showed that antibiotic exposure in early life was associated with a higher chance of asthma later on. Still, remarkably, antibiotics given later in life did not have the same effect. This shows that timing is also an important factor with antibiotics. One thing remains clear: changing the bacteria in our body has a greater impact than we first thought.
Antibiotics have been key to our survival over the past hundreds of years. That cannot be stated enough. Books like these are not asking us to throw out antibiotics. They are urging us to totally change how we look at microbes. Over the past decades, the focus in making antibiotics seems to have been raising their strength. It also seems to have been raising their profits through widespread use. The authors of Let Them Eat Dirt are wisely asking us to respect our body’s natural defenses. They want us to use those defenses to the full by using medicines with care.
Let Them Eat Dirt: Saving Your Child from an Oversanitized World
Blaser Explores Link Between Obesity, Antibiotic Use
https://nihrecord.nih.gov/newsletters/2014/11_21_2014/story1.htm
Antibiotics in fetal and early life and subsequent childhood asthma: nationwide population-based study with sibling analysis
http://www.bmj.com/content/349/bmj.g6979
Related reading
Sources
- Aversa Z, Atkinson EJ, Schafer MJ, et al. Association of infant antibiotic exposure with childhood health outcomes. Mayo Clinic Proceedings. 2021. PMID 33208243
Medically reviewed by Dr. Gurpreet Singh Padda, MD, MBA, MHP
Interventional pain physician, addiction medicine specialist and obesity medicine diplomate.
Licensed in Missouri and Illinois.
Last reviewed June 18, 2026
