The purpose of oral immunotherapy is not so someone can go to a baseball game and inhale a bag full of peanuts. Instead, it provides insurance — a buffer zone — so that in the event of accidental ingestion, the risk that a life-threatening reaction will occur is significantly decreased - Charles Feng
image by: Allergychoices, Inc.
I have terrible, awful, allergies to a whole bunch of things, from dust mites to apples to chlorine. And my list is only dwarfed by the number treatments I've tried over the years. I load up on over-the-counter antihistamines like Zyrtec and Claritin and get shots once a week, but it's still not enough.
I'm far from alone — one in five Americans has some type of allergy. And there's still really no definitive way to stop them completely in most people.
The whole thing has always made me wonder — why are allergies so incredibly hard to treat? And why aren't there better options?
What your body is doing when you have an allergy
Your immune system is designed to protect your body against attacks from stuff like bacteria that could harm it, but in the case of allergies, your immune system's efforts are misguided. Cat hair, or dust, or whatever you're allergic to is a false alarm, but your body doesn't know any better and attacks it anyway.
"The body misinterprets the environmental or the food allergen as being harmful," says David Lewis, allergy and immunology researcher at Stanford.
One of the major players in allergies is a class of proteins that the immune system produces called immunoglobulin E, or IgE. transition
For example, dust is one of my worst allergies — I have dust mite-specific IgE. It travels through my blood and attaches itself to mast cells, a type of white blood cell that are most common in the nose, throat, skin, and gastrointestinal tract where they're in a good location to defend against invaders.
In normal immune system reactions, mast cells help to heal wounds and protect against disease. But in someone who's allergic, the allergen, which is contained in dust in my case, triggers the creation of allergen-specific IgE. The IgE attaches itself to mast cells and tells them to release the chemical histamine, which then causes allergic symptoms such as sneezing or hives.
If you had an actual infection, symptoms like this would be your body's way of fighting against it and telling you that something's actually wrong. But in this case, there's no helpful function to all of this. Your immune system is simply overreacting.
And what's even more annoying is that once you have allergies, there's a good chance you're stuck with them. "The body's very good at holding onto immune responses," Lewis says. It's why vaccines work — because once your body knows to attack a substance, it will continue to do so. But it will also remember how to attack something it doesn't need to, like an allergen.
Variation in allergies makes it hard to find treatments that work for a lot of people
"It’s really hard to come up with specific strategies to deal with allergies that apply to a large population, because there’s so much individual variation," Lewis says.
Right now, treatments for allergies include anti-histamines like Zyrtec, steroids that suppress inflammation, and immunotherapy like allergy shots that can build up someone's tolerance to an allergen.
There are also some fairly recent developments. For example, some people with food allergies can build up tolerance by taking a tiny amount of their allergen each day. And one drug on the market, an injectable medicine called Xolair, can prevent some IgE in the body from attaching to mast cells and basophil cells (but is only approved for allergy-caused asthma in children over 12 and adults).
The options are limited. One reason there aren't more is that the varying degrees of allergies makes finding treatments new difficult. For many people with mild allergies, an antihistamine like Zyrtec might do the trick. But there's a whole range out there. To be considered allergic to something, your IgE level targeting that allergen has to be at least 0.7 IU/ml of blood. My pesky dust allergy, last time it was measured, was nearly 4,000. So what works for someone with mild hay fever might not work for me, and what works for me definitely wouldn't work with someone with hypersensitive allergies and an IgE level in the tens of thousands.
Testing is tricky because lab mice don't develop allergies the same way humans do
To develop a new treatment for allergies, scientists first have to test it. And to try it out in humans, they usually have to show its effectiveness in animals first.
But lab animals like mice and other rodents don't develop allergies spontaneously like humans do. Scientists can understand certain parts of the immune responses, like how allergy symptoms work, but those methods "leave a lot to be desired," Lewis says.
"That has definitely slowed down the field quite a bit," he says. So scientists can only study allergic reactions after inducing an allergy-like reaction in the mice. Researchers do this by repeatedly exposing mice to low levels of an allergen for up to three months. But the resulting response isn't really representative of allergies in people, which means that the drugs tested aren't guaranteed to work in people the same way they work in animals.
It's difficult to track allergies over a long-term period
It's important to look at how allergies evolve over time in one person, starting with when they're young and going on for years, Lewis says. That's because while allergies don't usually go away, they do wax and wane.
These types of longitudinal studies could clue researchers in on how best to intervene in an allergy's development. But parents aren't exactly excited about signing their kids up for such long studies, which are also expensive for scientists to perform, he says. And because of that, there isn't as much information available on the evolution of an allergy as researchers really would want.
We don't know exactly what's happening in an allergic reaction
IgE antibodies are the key to allergies, but unfortunately for researchers and allergy sufferers alike, they're very challenging to track in the body.
Using a blood test, doctors can see what general type of IgE you have, but not exactly what exact subtype or what specific substances it's reacting to. So take cat hair, for example — my allergist knows from my blood test that I have cat-specific IgE, meaning my body reacts when I'm around a cat. But what my allergist doesn't know is exactly which particles in cat hair my body (and my IgE) is reacting to.
If researchers knew what specifically IgE was reacting with, they'd be better able to create individualized treatments that target that particular molecular interaction and stop allergic reactions from happening.
Right now, scientists use a flagging system to look at IgE. Say someone's allergic to peanuts — a scientist can make a peanut protein with a little fluorescent tag that makes it detectable in a scan. They can then use a technology called flow cytometry, which suspends cells from a blood sample in fluid and passes them over a machine that detects the tagged allergen that's attached to the connected IgE and mast cell.
Researchers use this method to see what allergens an IgE antibody is reacting with, but the technique is so involved that it's not practical for doctors to use every day with patients. Technology is improving to detect them, Lewis says, but he doesn't think it will become significantly easier any time soon. So until researchers can overcome the hurdles to treating allergies, it looks like we're doomed to carry on sniffling and sneezing.
Source: Megan Thielking, Here's why there aren't better treatments for your allergies, Vox, March 3, 2015.