Seasonal allergies don’t make any sense. Anyone who has dealt with the puffy eyes, ceaseless sneezing, and insatiably itchy mouth cause by allergies has tried to figure out the purpose of their misery, only to learn this sad lesson. “It’s the body gone awry,” says Dr. Martha White, allergist and director of research at the Institute for Asthma and Allergy. “There not necessarily a logical rhyme or reason.”
Although you won’t find a satisfying justification for why your body reacts to cats and dust in such a maddening way, you can have some level of understanding about where these reactions come from and how you can combat them.
Allergies Versus Parasites
The human body is not a perfect machine but the allergic fit it can produce in the face of something that should be harmless, like tree pollen, does serve a purpose. “It’s acting very much like there’s a parasite that you’re trying to get rid of,” says White. “The body essentially views normal things in the environment the same way it would a parasite.” In other words, the symptoms we recognize as allergies are side effects of the body’s attempt to get the proper immune cells to the site of the invader, the allergen that it has mistaken for a harmful parasite.
The Role of Histamine
A big player in the body’s defense against these parasite pretenders is histamine, a substance released as part of our immune response. Histamine is a vasodilator, meaning that it opens up blood vessels. “Mast cells that contain histamine line all of the blood vessels and it’s part of what regulates the leakiness — or lack thereof — of blood vessels,” says White. Histamine also promotes secretion of other fluids. In the case of a parasite, vasodilation and these secretions would help get white blood cells to the problem areas. In the case of hay fever, histamine just makes people a mess.
Allergies as We Age
It is true, unfortunately, that people can develop allergies at any age. It all depends on exposure and your genes. Let’s say your genes have decided ragweed is harmful. Upon your first exposure to ragweed (which might not be until you’re 30), your body creates very special versions of the antibody Immunoglobulin E (IgE). These are custom designed for the allergen it has decided is a threat. Once this IgE has been created, it binds to mast cells, now primed for the next exposure. Upon re-exposure, the IgE of the mast cells binds to the allergen and the allergic response, helped along by histamine, begins.
This is why people need to be wary of bee stings even if they’ve been stung before. “The fact that you managed to survive the first reaction does not by any stretch of the imagination mean that the next will not be bad,” says White.
The nose is the classic target of allergies. Running, sneezing, itching, stuffiness, and post-nasal drip are the all common symptoms of someone in the throes of allergy season. When histamine is released, it goes to work quickly, opening up vessels. Tissues swell, mucus production increases, and itchiness ensues as nerve cells react to the histamine. Other chemical mediators that work alongside histamine can also contribute to stuffy noses
If an allergic reaction triggers the mast cells in the lungs, symptoms such as wheezing, increased mucus production, and shortness of breath may result from the inflammation these cells promote. It is common for people who suffer from rhinitis (inflammation of the nose) to also have asthma, and vice versa. Allergic asthma, asthma brought on by an allergic reaction, is the most common form of asthma. It affects approximately half of all people with asthma.
Just as histamine opens up vessels in the nose and lungs, it can also affect the eyes. Itchy, red, and watery eyes are all commonplace for people with allergies. Because the eyes can also act as an entryway for allergens, people who are allergic to pollen are encouraged to wear sunglasses as a protective measure.
Histamine, again, is the main culprit when it comes to allergic skin reactions. Most often, these reactions come in the form of hives. These itchy, red dots or blotches result from fluid leaking out of the dilated blood vessels into the surrounding tissue. When this happens at a deeper level, it’s called angioedema. Although stress can seem to cause hives, the link between these two may be that stress throws off the immune system, worsening the unnecessary reaction that’s already underway.
Difference Between Colds and Allergies
White says that one of the most common questions that she is asked is whether they have a cold or allergy — and what’s the difference anyway? And it’s a tricky one. Colds and allergies can have very similar symptoms, even itching. If you seem to get a cold at the same time of year, every year, it might be seasonal allergies because you are reacting to something, like pollen, that works on a yearly cycle. If you’re starting to feel under-the-weather as someone who had similar symptoms is feeling better, that might be a cold because people allergies aren’t contagious. One trademark of allergies that might reduce confusion is that, although called “hay fever,” allergies do not cause fever.
A look at what’s causing problems in the nose, lungs, skin, and eyes gives us a good idea about why antihistamines are a common treatment for allergies. These medications work by binding to histamine receptors, blocking histamine from doing so and otherwise starting the cascade of allergy symptoms. “The antihistamines work the day you use them,” says White. “They don’t do anything long-term in terms of cutting down on the allergic reaction.” Antihistamines are very effective but are only half of the one-two punch many people with allergies use.
What Nasal Steroids Sprays Do
To get ahead of the allergy game, we turn to nasal steroid sprays. These (usually prescription) medications work on various cell types and chemical mediators in order to control inflammation. Unlike antihistamines, steroid sprays do have long-term effects and tend to help more when people start to use them early in the allergy season.
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