Dr. María Barcena
Before discussing allergies, we should first understand what the word “allergy” means. Allergy is basically a mistake of the immune system, where the body is trying to defend itself against a harmless substance. So, instead of the body normally ignoring a cat dander particle, an immune response is set up to fight it off as if it were an infectious organism. In this example, chronic exposure to cat dander leads to a cold-type syndrome that never seems to go away.
When allergens are airborne and are inhaled, they lead to syndromes such as allergic rhinitis (sneezing, nasal congestion, etc.) or asthma. When allergens are ingested, they lead to the symptoms of food allergy and drug allergy.
So why are allergies becoming more common? One theory is that the clean living in our modern society, leading to the lesser exposure to invading organisms, contributes to this “allergic” mistake of the immune system. Also, the overuse of antibiotics in children probably leads to the same result. In addition, pollution, by unknown mechanisms, seems to lead to allergy. Lastly, as far as food allergies go, it appears that delaying infant feeding of certain “allergenic” foods leads to more allergies.
Science has provided a few hints on the “primary” prevention of allergy – that is, not becoming allergic in the first place.
First, having more children at home, and consequently having them share more viral infections, leads to fewer of the children having respiratory allergies. Also, likely from exposure to animal waste, being born on a farm or being exposed to pets at birth appears to lead to less allergies (note that once you are allergic to an animal, the animal is best removed). Also, fresh air, exercise, sunlight (Vitamin D) and healthy fats in the diet appear to lead to less allergies. Here you can see why children in modern industrialized societies are more allergic.
Exposure to dust mites in infancy, however, seems to lead to more respiratory allergy. Dust mites are microscopic creatures that live indoors, especially in moist and warm environments. Since our children spend more time indoors than they have in the past, this is another reason allergies are on the rise. Studies have shown that less dust mite exposure in infancy leads to less asthma, for instance.
As to the primary prevention of food allergies, studies over the last few years have told a fascinating story. About 20 years ago, allergy researchers noted an increase in food allergy, especially to milk, eggs, and peanuts. A theory developed that by delaying infant exposure to these foods until the “immune system matured,” we could reverse the trend. As it turned out, the opposite occurred. Essentially, a food allergy epidemic came into existence.
This is where the story gets interesting. Some very smart researchers noted that different countries and cultures had different rates of food allergy. Peanut allergy, for instance, seemed to be almost nonexistent in Israel compared to other Western countries. So, one group of scientists decided to compare the Israeli infant feeding habits to a genetically similar group of children in another country (Jewish children in Israel versus Jewish children in England). What they found was that Israeli children were being fed peanut-containing snacks starting at only a few months of age. Whereas, like the United States, English parents (following national guidelines) were not giving their children peanuts until about two years of age or later. So, they came up with the hypothesis that delayed feeding of peanuts was leading to the increase in allergy.
As good scientists do, they decided to test their theory. They enlisted a group of parents who agreed to have their babies enter a study where some were given peanut -containing snacks at about four months of age, whereas the others were not given peanuts until they were five years old. They then followed these children for several years to see who developed peanut allergy. They studied only children with severe eczema or pre-existing egg allergy, as they thought that this group was at the highest risk for peanut allergy.
The results of this study were published in 2015 in the New England Journal of Medicine. They found that early peanut introduction led to a dramatic decrease of peanut allergy at five years of age – 2% in the early group, versus 14% in those with the delayed introduction of peanuts. A study following this by the same researchers found that the effect was long-lasting.
As a result of this, US feeding guidelines for infants have recently changed. The new guidelines, issued by the National Institute of Allergy and Infectious Diseases in January 2017, recommend giving babies puréed food or finger food containing peanut protein before they are 6 months old, and even earlier if a child is prone to allergies and doctors say it is safe to do so. They caution to never give a baby whole peanuts or peanut bits, because they can be a choking hazard. So, new and future parents should be asking their pediatrician about when to start peanut-containing foods in infants. Studies are ongoing regarding other foods such as milk and egg, but no answers are available yet regarding the best strategy for these foods.
“Secondary prevention,” or what to do when you are already allergic.
As far as food allergies are concerned, there is no secondary prevention besides strict avoidance of the food, as well as carrying an epinephrine self-injectable device for accidental ingestions. It should be noted that many children outgrow their food allergies, so food-allergic children should be followed by an allergy specialist to see if and when certain foods can be safely introduced.
If one is allergic to airborne allergens, there are strategies to avoid exposure. Animal dander exposure can be lessened by rinsing the animal with water twice a week and with the use of HEPA air room filters. Obviously, if someone is allergic, the removal of the animal from the home is the best strategy. Dust mite exposure can be decreased by frequent washing of bedding, removal of carpeting, and by placing dust mite-proof encasements around pillows and mattresses. Also, weather permitting, allowing fresh air into the home decreases dust mite exposure. Mold growth in the home can be especially problematic for those with allergies, so removal of any water damaged materials in the house is important. As far as pollens, there is no particularly ideal way to avoid these allergens since being outside is so healthy otherwise. However, avoiding being outside on particularly windy days is a reasonable idea.
Lastly, another prevention strategy for existing airborne allergies is allergen immunotherapy injections or allergy shots. This treatment has been around for many decades and is still the only effective method for actually decreasing the immune allergic response of an individual. Unlike medications that only treat the symptoms, allergy shots get to the core of the problem and alter the patient’s immune system to make them less allergic.