A Patient's Guide to Allergies

More than 50 million Americans suffer from allergies of one kind or another -- making this the sixth leading cause of chronic illness in the United States, according to the Centers for Disease Control and Prevention.

These include environmental allergies like dust mites indoors or pet allergies that persist year-round, as well as seasonal allergies, like pollen. Many people have hay fever, or allergic rhinitis, which is set off by all sorts of allergens inside and outside, from pet dander to pollen from grass, weeds and trees, plus other irritants like perfume. What's more, food allergies affect around 8%, or 5.6 million kids, and more than 10%, or over 26 million, adults, according to research published in Pediatrics and JAMA Open Network.

The incidence of allergies, including food allergies, seems to be increasing. While it's difficult to tease out exactly how much of that is because of increased awareness and diagnosis, experts say it appears there's been a real rise.

It's not precisely clear what might account for that, though theories abound, like the so-called hygiene hypothesis. That posits that our modern obsession with cleanliness has left children less exposed to germs that equip their immune systems to tackle real threats. And so, as it relates to allergies, "our bodies are looking for something to basically attack," explains Dr. Joseph T. Inglefield III, an allergist in Hickory, North Carolina, and a fellow of the American Academy of Allergy, Asthma & Immunology.

[See: 8 Surprising Facts About Asthma and Seasonal Allergies.]

Generally speaking, all allergies have in common the immune system's overreaction to things, such as grass, pollen or various edibles that are generally harmless and don't threaten the body as a disease -- or for that matter an invasive bug or worm -- would. "But our body starts to perceive because of repeated exposures that it is a parasite," Inglefield says. "So the body turns on the arm of the immune system that's been developed to protect us from parasites."

As the body tries to rid itself of the perceived threat, a person develops symptoms that can range from mild to severe and dangerous. Those may include:

-- Itchy, watery eyes.

-- Runny, stuffy nose.

-- Sneezing.

-- Hives, or red bumps that can itch on the skin.

-- Stomach cramps.

-- Vomiting.

-- Wheezing or difficulty breathing.

-- Feeling faint or light-headed.

In the most dire scenario, a person may experience anaphylaxis, or anaphylactic shock, a severe life-threatening allergic reaction, for example to foods like nuts, eggs or shellfish, an insect sting, medication or latex. In the most serious cases, anaphylaxis can result in swelling of the airways that prohibits breathing or a dangerous drop in blood pressure, which can be fatal.

Causes and Prevention

Antibodies, or blood proteins, are produced to counteract antigens -- diseases and other foreign substances that induce an immune response. And the antibody immunoglobulin, or IgE, causes allergic reactions. Along those lines, certain people are more likely than others to have this so-called IgE-mediated reaction to one or more allergens, whether that be a mold spore or a medication, pet dander or pollen.

Factors that increase the risk for developing allergies include being a child -- although many adults also develop new allergies -- and race, where minorities including African-Americans, Hispanics and Asians are at higher risk than whites. Most strongly influencing one's chances of developing allergies is genetics, or a family history of allergies.

While you can't change who you're related to, there are some things families can do that may lower a child's risks of developing allergies.

Breastfeeding is promoted to bolster overall health and immunity, and when foods are introduced, it's recommended that kids get a wide variety.

Food avoidance was once encouraged as a strategy, but in healthy children without present allergies that's not advised today. That's because the latest data indicates that introducing some potentially allergenic foods, like peanuts, early could be protective. In particular, research on infants at high risk for developing a peanut allergy shows that when they were given peanut butter products when they were at least four months old and less than 11 months, they were far less likely to develop a peanut allergy.

"This was a really big breakthrough," says Dr. Ruchi Gupta, a professor of pediatrics at Northwestern University Feinberg School of Medicine and a pediatrician at Ann and Robert H. Lurie Children's Hospital of Chicago, who has led separate research on food allergy prevalence, including the studies published in Pediatrics and JAMA Open Network.

In other cases, it's still thought that limiting certain exposures may help, like with dust mites that might trigger allergy or asthma symptoms. "If your child is at high risk of developing allergies, there are steps you can take to control dust mites," the American Academy of Allergy, Asthma & Immunology notes. "Use zippered, 'allergen-impermeable' covers on pillows and mattresses and wash bedding in hot water weekly. Indoor humidity should be kept below 50%. If possible, carpets and upholstered furniture should be removed from your infant's bedroom."

What's more, secondhand smoke exposure may increase children's risk for asthma and potentially allergies as well, even possibly food allergies. The evidence is mixed on the latter though, as other research supports a link between tobacco smoke exposure and rhinitis or nasal symptoms, like runny nose and stuffiness, but not development of allergies.

[See: 12 Medical Emergencies You Need to Address Right Away.]

Diagnosis

For all those who have a doctor-diagnosed allergy, many more report that they think they have allergies -- but have never confirmed it. Researchers find, for example, that a significant proportion of people who think they're allergic to food aren't -- and may be avoiding it unnecessarily. What's more, some people may have a food intolerance, or another distinct issue like celiac disease, in which wheat causes an immune response -- rather than, say, a wheat allergy. (In that case, problems attributed to celiac disease or non-celiac gluten sensitivity often aren't, so sorting that out can be important too.)

"There are so many food-related conditions," Gupta says. "So getting into an allergist and getting tested is really critical to truly determine if it is a real food allergy, and then to learn how to manage it."

In addition to going over a person's family history and discussing symptoms, allergy testing is frequently done to home in on what precisely is causing the allergic reaction. "The most accurate method is skin testing -- where we take a little bit of the allergen and we expose the person's skin to that and see if they develop an allergic reaction on the skin," says Dr. Thomas Luft an internist at UnityPoint Health practicing in Pekin, Illinois. "We look for a little welt that kind of looks like a mosquito bite -- it turns red, and kind of itchy -- that tells us they're allergic to that particular or specific thing."

Allergy blood tests are also sometimes used. In that case, instead of taking the allergen to the patient and testing it on their skin to see if they're allergic, blood is drawn and taken to the lab to test for allergy-specific antibodies. But this type of testing is less sensitive and accurate than skin testing, Luft says.

Allergy Management

Some people who have an allergy to a specific food, for example, develop a natural tolerance to that food with age, so that they essentially "grow out" of their allergy. But there's no cure, per se, for allergies.

Even so, there are a number of things that can be done to reduce or even essentially eliminate ongoing symptoms, the most powerful of which is to avoid the allergen. In some of the most dramatic examples, people who move to a different area where certain pollens or grasses that triggered allergic reactions aren't prevalent, report experiencing dramatic improvement. And in a simpler more confined scenario, a person who is allergic to cat dander, who doesn't keep a cat in the home and avoids encountering cats elsewhere can also avoid uncomfortable allergic reactions (until, that is, unexpectedly encountering a feline).

Avoiding the allergen is first and foremost key and by far the most successful strategy, Luft says. However, he and other experts note that to do this 100% of the time, in all scenarios, is often impossible.

So medications like antihistamines and steroids that are available over-the-counter as well as some prescription medications are sometimes recommended to reduce symptoms, like those that may occur with seasonal allergies.

In some cases where symptoms are more severe and persistent and to avoid long-term medication use, allergy shots, or immunotherapy, may be recommended. "That's exposing them to just very tiny amounts of the allergen incrementally," Luft explains, so that the person's immune system adjusts. "Then they have less allergic response when they're exposed to an allergen."

This involves getting regular injections of increasing amounts of allergens initially about once or twice a week during a build-up phase usually lasting from three to six months. Then during the maintenance phase injections are given with longer periods of time in between, ranging from two to four weeks, according to AAAAI.

It can take a year to see improvement, and shots are generally continued for three to five years. After that, a wait-and-see approach is typically taken -- where some patients do well after the shots are stopped, and others see symptoms return that require additional treatment.

With any medications -- even those obtained over the counter -- it's important to discuss side effects, and that's especially true for drugs taken on an ongoing basis. Side effects vary by the drug but can include drowsiness, and even in some cases an allergic reaction to an allergy medicine. The primary risk with allergy shots is having a severe allergic reaction to the allergen up to anaphylaxis. Given that, it's always important that allergy shots are administered in a doctor's office where swift action could be taken if a severe reaction occurs to prevent serious problems from occurring, Luft says.

[See: Is it Healthy to Sleep With Your Pets?]

In addition, epinephrine auto-injectors are prescribed; these can be self-administered if a person is in the throes of a severe allergic reaction. While it's a simple injection, experts emphasize it's still critical to be educated by a health provider in advance and trained on how to use the auto-injector. That's key to avoid hesitancy when the medication, which relaxes airway muscles and tightens blood vessels, is needed ASAP to reverse effects like wheezing or difficulty breathing and dangerous drop in blood pressure.

Michael O. Schroeder has been a health editor at U.S. News since 2015. He writes health stories on a wide range of topics from mental health to medication side effects, and he manages the blog For Parents.

Michael has reported on health and wellness since 2005, and he's also covered everything from business news to governmental affairs for various newspapers. His stories have also been published in HuffPost, MSN, Yahoo!, WTOP, The Washington Post and The Indianapolis Star. He's also an active member of the Association of Health Care Journalists.

Michael has a bachelor's degree in English from Wabash College and a master's degree in journalism from Indiana University.

You can follow him on Twitter or email him at mschroeder@usnews.com.