The War Within
If you’ve ever experienced the infernal itch of poison oak or sneezed your way through hay fever season, you know allergies can make life miserable.
But when you’re fighting to keep a patient’s airway open, or struggling to save a child whose blood pressure is bottoming out from the simple mistake of eating a strawberry, you understand the magnitude of what a powerful weapon the immune system can be when it turns on itself.
“Childhood is like field testing for the immune system. Although some allergies develop later, the early years are where most problems begin to show up,” Children’s Hospital pediatric allergy specialist Prescott Atkinson, MD, said.
“Allergy is a broad term. Someone may say they are allergic when they get a rash, but something like contact dermatitis from poison oak differs in both severity and how it occurs. It is mainly a slowly developing T-cell process that peaks two to three days after exposure. It’s uncomfortable, but it shouldn’t be life threatening,” Atkinson said.
“The more serious allergic reactions we see are usually immediate and involve the IgE system. In the past, it protected the body against parasites. Now, in the developed world, there are fewer parasites, so that part of the immune system has nothing to do. The trouble begins when the IgE system goes looking for things to do and starts reacting against things it shouldn’t,” Atkinson said.
In the last half of the 20th Century, there was a dramatic increase in the prevalence of allergies and that trend is continuing. Serious food allergies are increasing and respiratory allergies are also rising. The question is—why?
“Some research suggests that Vitamin D plays a role in modulating the immune system and keeping it on track,” Atkinson said. “Another theory is the hygiene hypothesis. Some of the most convincing evidence in that area is research that has been done in Europe.”
According to the theory, Western society’s improved sanitation isn’t giving the immune system of the developing fetus an opportunity to be fine tuned by contact with more benign bacteria while in utero. When the child’s immune system develops without learning to recognize what is harmful and what isn’t, it tends to overreact. Support for this idea can be found in numerous studies of isolated rural populations where there seems to be a correlation between a low incidence of allergies and mothers who worked in barnyards and with cattle while pregnant.
The human microbiome and its role in health has also been a major recent topic. Is it possible that some of our new defenses against harmful organisms are also eliminating helpful organisms that play a role in keeping other problems in check? There’s also the concern that humans are coming into contact with a broad spectrum of new substances that weren’t present as our genome evolved.
“Regardless of the cause, the question remains—why does this person develop an allergy to this particular substance and not everyone else? There is something specific to the individual that determines who reacts to what,” Atkinson said.
Avoidance is the first line of defense in dealing with food and contact allergies, though in an age of prepared food, restaurants and food in social situations, avoiding food allergens isn’t always easy.
“With things like foods and bee stings, avoiding doesn’t always work, so you need to be prepared,” Atkinson said.
In addition to antihistamines and epi pens for emergencies when symptoms of anaphylaxis threaten, for some types of allergies, desensitization may be a helpful strategy.
“Injections with a small amount of the allergen can often be helpful in retraining the immune system. Researchers are now working on simpler methods of desensitization, including oral dosing, which could soon be more widely available,” Atkinson said.
When a patient comes into an allergy doctor’s office, the first issue is determining whether a patient really is allergic, and if so, to what.
“Many people think they are allergic to penicillin when they aren’t. There’s also a lot of talk about being allergic to gluten. While there is such a thing as celiac disease, it’s important to distinguish between food sensitivities and food allergies. True food allergies are more common in children. Some are allergic to wheat, but the more common food allergies include nuts, dairy, eggs, and seafood.
“The more serious reactions to food tend to happen quickly and often require immediate medical care,” Atkinson said.
One exception to the immediate reaction to food that recently came to light is the delayed reaction to mammal meats in people who have been bitten by the Lone Star tick. The reaction can be severe, and may include anaphylaxis.
“The Lone Star tick has spread throughout the Southeast and the link to delayed reactions in humans who eat beef, pork, lamb and other mammal meats was first identified in Virginia. It is a deer tick, and we may be seeing more cases, especially in people who spend time in the woods.”
Eczema also seems to be more common in recent years. It may involve contact allergens and in some cases could also be related to food sensitivities.
“Some people seem to be born with both skin and digestive tissue that are more permeable and allow particles to get through that shouldn’t be getting through. The immune system reacts, and both skin and digestive symptoms can develop.
“With research, perhaps we’ll identify what’s missing that allows allergies to develop in some people and not in others,” Atkinson said. “It could be as simple as learning that folic acid helps to prevent spina bifida. Eventually, we may be able to prevent allergies instead of just treating them.”