Protecting our Children from Allergic Diseases

If asked to guess the top ten chronic illnesses within the United States, what would you include in your list?  Diabetes, hypertension, and likely cancer to name a few, but would you include allergies?  Nearly 50 million individuals living in the United States suffer from allergic diseases, and it is likely you or someone you know has experienced them as well.  For many, symptoms are chronic, detrimental, and impact daily living.  But, what if there was a way to prime our children in hopes of mitigating their risk of battling such atopic diseases?  The hygiene hypothesis may do just that.

WHAT IS THE HYGIENE HYPOTHESIS?

The hygiene hypothesis: a belief that an early exposure to particular infectious agents may actually protect our immune system from developing allergic diseases later in life.  In recent years, advancements throughout the Western world have decreased the incidence of countless infectious diseases that previously impacted the lives of many.  Meanwhile, the rising prevalence of atopic and autoimmune diseases has led many to study the correlation between the two and factors that may influence their interconnected relationship.

THE IMPORTANCE OF DEVELOPING A STRONG IMMUNE SYSTEM

When a fetus develops within the mother’s womb, their immune system is suppressed so the fetus does not reject the mother’s tissue.  Rather, during this time, the fetus relies on the mother’s antibodies for protection.  However, upon birth, the newborn is now dependent on their own immune system to ward off infections.  In order for their immune system to mature appropriately, the child must face age appropriate immune challenges to prime, strengthen, and expand the “knowledge” of the immune system.  So, what do these challenges look like and how can their presence, or lack-thereof, alter the likelihood of your child developing atopic or autoimmune diseases?

PROTECTIVE AND RISK FACTORS CONTRIBUTING TO ALLERGIC AND AUTOIMMUNE DISEASE

As noted, early childhood is a time in which various protective and risk factors are believed to impact allergy development.  Such factors play a role through altering the microbiome of the skin, nasopharynx, lung, and gut of the developing child.  Below we will analyze the following: mother to fetus transmission, infection history, social exposure, environment, and diet.

Mother to Fetus Transmission

There are various pathways in which transmission between mother and fetus takes place throughout pregnancy, birth, and early childhood.  During pregnancy, the maternal diet is believed to impact the likelihood of the fetus developing allergic disease later in life.  Studies have indicated an inverse relationship between maternal consumption of eggs, raw vegetables, and cooked green vegetables during pregnancy with the prevalence of allergic disease.  Furthermore, mode of delivery has been shown to play a critical role in the prevalence of developing allergic disease later in life.  Research suggests that those children born through vaginal delivery are exposed to various microbes within the vaginal tract and fecal matter of the mother.  These microbes colonize the gut and support the early immune system of the child.  On the other hand, those born through cesarean delivery are not exposed to the same microbes and bacteria.  As a result, they tend to experience an increased prevalence of allergic disease throughout their lifetime.  Finally, children who are breastfed in early childhood are believed to be less likely to develop allergic diseases.  While the mechanisms of this are not well understood, breastfeeding ultimately leads to maturation of the immune system through the transmission of antibodies, which allows it to be primed for challenges later in life.

Infection History

Over the years, developments in technology, advancements in vaccines, and improvements in sanitation and water quality have led to an overall decrease in infectious diseases.  While this is great for the general population, some early exposure to certain pathogens in utero through both maternal vaccination and maternal infection is thought to be beneficial in helping prevent the development of allergic disease in the child later in life.  Such exposure allows the immune system of the fetus to “learn” these pathogens based on the passive antibodies they have obtained from their mother.  By learning to recognize the infectious agents, it is more likely that the immune system will be able to defend itself from them upon future exposure.  On the contrary, the use of antibiotics to treat infections in young children is believed to negatively affect a child’s protection against allergic diseases.  The manner in which antibiotics kill both beneficial and harmful bacteria is detrimental to the early childhood immune system.  This early elimination of the gut microbiome is believed to lead to an increased likeness of atopic disease.

Social Exposure

The environment in which our children are raised plays  a major role in their probability of developing allergic diseases.  Many studies suggest that children who are raised in large families or who attend daycare and have regular interaction with other individuals are often less likely to develop allergies later in life.  Their continued interactions with other humans increases their encounters with various germs, microbes, and pathogens which only further strengthens their immune system.

Environment

Current literature suggests that children who are raised on farms or experience regular farm exposure are often less likely to suffer from atopic diseases later in life.  It is believed the inhalation of endotoxins, which are contaminants of agricultural dust, and various associated microbes challenge the immune system at an early age.  As a result, the immune system is strengthened for future threats, decreasing the child’s likelihood of experiencing allergen sensitivities in the future. 

Diet

Similarly to breastfeeding, the early diet of children can impact their probability of developing allergic diseases.  Studies indicate that early childhood consumption of single ingredient foods including fruits and vegetables aids in strengthening their overall immune system.  With a strengthened immune system, they experience a decreased incidence of developing atopic diseases.

WHAT CAN WE DO TO PROTECT OUR CHILDREN?

In a world that is currently so fixated on eliminating all germs and diseases, it can be concerning to wonder how these choices will impact the long term health of our children.  While the hygiene hypothesis has not yet been scientifically proven, the data suggests that some early childhood exposure to particular microbes is likely to decrease the possibility of the development of allergic disease later in life.  While nothing is guaranteed, it is possible that developmental milestones such as breast feeding children when possible and having them attend daycare may lead to a life with minimal incidence of allergic disease.  If you have any questions regarding your child’s risk, please consult with an allergist.