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Allergic Reactions

These can range from mild to life-threatening.

We all overreact to certain situations in life—some of us more than others (slowly raises hand). But when your immune system overreacts to a harmless substance, also known as an allergen, your body responds by triggering an allergic reaction—the runny nose, watery eyes, itchy skin, sneezing, and wheezing you experience when you’re just trying to pet your dog or enjoy a beautiful spring day.

Allergies are one of the most common chronic diseases and impact more than 50 million Americans each year, according to the American College of Allergy, Asthma, & Immunology (ACAAI). More specifically, they are the sixth leading cause of chronic illness in the United States.

“An allergic reaction is due to a sensitization of our body’s immune system to an outside allergen,” Omid Mehdizadeh, MD, an otolaryngologist and laryngologist at Providence Saint John’s Health Center in Santa Monica, California, tells SELF. In other words, an allergy occurs when the immune system sees a substance as harmful (even though it’s not) and overreacts to it.

Identifying potential allergens that cause you to sneeze like crazy or break out in hives can help you differentiate between mild reactions that are manageable at home and severe reactions that scream, “Get to the emergency room right away!” Here is everything you need to know about the types of allergic reactions, common symptoms, causes, and how to treat them.

Allergic reactions can range from mild to severe and can be life-threatening.

Amanda K Bailey

So, what exactly are allergic reactions?

It’s no secret that your immune system works hard to protect the body from viruses, diseases, and infections. However, in some people, the immune system sees a non-threatening substance (an allergen) as harmful, which sets off a whole host of reactions. Your body responds by making antibodies called immunoglobulin E (IgE), which cause certain cells to release chemicals like histamine into the bloodstream to defend against the allergen. This sets off a cascade of symptoms that you know of as an allergic reaction.1

Allergic reactions can range from mild to life-threatening and may cause symptoms in the nose, sinuses, throat, lungs, ears, skin, or lining of the stomach, according to the American Academy of Asthma & Immunology (AAAAI). While not an exhaustive list, Dr. Mehdizadeh says foods—like gluten, dairy, soy, shellfish, and nuts—pollen, metals, ragweed, dust mites, grasses, and dander, top the list of common allergens.

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Are there different types of allergic reactions?

If it seems like the list of allergic reactions is long, you’re not mistaken. Allergic reactions can affect your eyes, nose, skin, and lungs. Clinically, experts even distinguish between different classifications of reactions. “There are different types of allergies and allergic reactions, which are classified by the types of cells involved,” Edith Schussler, MD, a pediatric allergy and immunology specialist at Weill Cornell Medicine and New York–Presbyterian, tells SELF. Dr. Schussler says type 1 reactions are immediate, and the type most people think of when talking about being allergic to something like pollen, pets, or food.2 “It’s also the type that is mediated by IgE antibodies and may cause anaphylaxis,” she explains. Type 2 through 4 allergic reactions involve different body processes and chemicals and are typically more delayed reactions than type 1. Because type 1 allergic reactions are what most people experience, that’s what we’re going to focus on here.

Type 1 allergies generally produce symptoms quickly—within a few seconds to minutes. They include food allergies such as peanuts, tree nuts, milk, soy, egg, fish, and shellfish, as well as environmental allergies related to pollen, pets, and other allergies that result in a runny nose, congestion, watery itchy eyes, and postnasal drip. Some but not all drug allergies are IgE mediated, meaning they fall in line with type 1 allergic reactions, says Dr. Schlusser.

Here are a few more details about how type 1 allergic reactions typically show up:

  • Nasal: Hay fever or allergic rhinitis, which can be seasonal or happen yearlong, causes inflammation in the nasal lining and increases  sensitivity to inhalants. Common triggers are pollen, pet dander, mold, dust mites, smoke, strong odors, or changes in humidity and temperature.3
  • Eyes: When an allergen irritates the conjunctiva (the white part of your eye) you may experience what’s called allergic conjunctivitis or ocular allergy.4 This produces symptoms like itching, swelling, and redness in the eyes. Nasal and eye symptoms often occur together. Causes include pollen, mold spores, dust mites, and pet dander, per the AAAAI.
  • Skin: When your skin comes into contact with an allergen, you may experience atopic dermatitis or eczema, which causes your skin to itch, flake, peel, or get red. Hives, which are red itchy bumps on the skin, are another common allergic reaction symptom. These can be large or small and often occur in clumps. Causes for hives include physical contact with an allergen (including foods), heat, medications, or insect bites, according to the AAAAI.
  • Lungs: Allergic asthma causes inflammation and swelling inside the airways of the lungs, making it difficult to breathe when you inhale an allergen. Allergic asthma is typically triggered by allergens like pollen, pet dander, dust mites, mold, tobacco smoke, or strong odors, per the Asthma and Allergy Foundation of America (AAFA).
  • Food allergy: This is one of the few allergies that can cause anaphylaxis, which is a life-threatening condition (more on this in a bit). Common food allergies include cow’s milk, eggs, fish, peanuts, shellfish, soy, tree nuts, and wheat, according to the AAAI. Coming into contact with a food allergen can cause hives, nasal issues, vomiting, stomach cramps, diarrhea, throat tightness, wheezing, chest tightness, trouble breathing, and tingling in the hands, feet, and lips.5

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What are common allergic reaction symptoms?

Not everyone will experience symptoms the same way. Some symptoms are considered mild and manageable, while others can be severe and require medical attention, according to the AAFA. Also, some allergens can trigger different reactions or may get worse with repeated exposure to the allergen. That’s why it’s important to understand the potential symptoms you may experience. With that in mind, here are some of the more common mild and severe symptoms that can happen from an allergic reaction.

Mild symptoms

  • Sneezing
  • Watery, itchy eyes
  • Runny nose
  • Itchy nose
  • Skin rash
  • Hives
  • Scratchy throat
  • Coughing

Severe symptoms

  • Stomach pain or cramps
  • Diarrhea
  • Bloating
  • Nausea or vomiting
  • Tongue swelling
  • Face or eyes swelling
  • Throat closing
  • Chest tightness
  • Wheezing
  • Loss of breath
  • Dizziness, feeling faint, or blacking out
  • Weakness
  • Hives

Severe symptoms can be a sign of anaphylaxis, which is the most serious allergic reaction you can experience, according to AAFA. Anaphylaxis requires immediate treatment in order to avoid life-threatening complications. It's important to note that hives accompanied by any of these severe symptoms are considered anaphylaxis, and should be treated as such.

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How are allergic reactions diagnosed?

Sure, Google is full of lists and self-assessments offering an internet diagnosis, but the only way to accurately diagnose an allergy is to see your doctor. In addition to a physical exam and medical history, your doctor may recommend testing to measure your body’s response to specific allergens. Allergy tests include a skin prick test, intradermal skin test (the allergen is injected), patch test, blood (IgE) test, and a challenge test, typically used with suspected food allergies.

“Allergy testing for type 1 allergies is typically done using prick skin tests and blood tests for specific IgE antibodies,” Dr. Schussler says. Skin tests involve pricking your skin to expose you to small amounts of protein in a potential allergen. If you develop a hive or raised bump at the test site, you’re most likely allergic to that allergen, per the Mayo Clinic. Blood tests, on the other hand, measure the amount of IgE or immunoglobulin E antibodies in your blood, which can reveal if you’ve developed a sensitivity to a certain allergen.

During anaphylaxis, Dr. Schussler says a doctor may draw a serum tryptase level (a protein in the blood that’s associated with allergic reactions) to confirm anaphylaxis, but it must be drawn within the first two hours of the event.

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What triggers allergic reactions?

Even a brief encounter with an allergen can cause a reaction. So, in order to prevent symptoms from occurring, it’s best to avoid the trigger. With that in mind, here are the most common things that can trigger allergic reactions, according to the AAAAI:

  • Pollen
  • Pet dander
  • Mold
  • Dust mites
  • Plants
  • Foods, specifically cow’s milk, eggs, tree nuts, fish, soy, wheat, peanuts, and shellfish
  • Insect stings like yellow jackets, honey bees, paper wasps, hornets, and fire ants
  • Medications, such as aspirin, non-steroidal anti-inflammatory medications, anticonvulsants, monoclonal antibody therapy, and penicillin
  • Latex

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What are the treatment options for allergic reactions?

Dr. Mehdizadeh says first-line treatments for allergies include avoidance, antihistamines, and epinephrine for severe reactions. Steroids may be given as well. For severe reactions that compromise your overall breathing and blood pressure, he says I.V. hydration, I.V. steroids, and intubation (when a tube is inserted to keep your airway open) may also be necessary.

The best way to treat allergies is to avoid the offending allergen altogether. If it’s a food allergy, for example, you are asked to avoid eating it. Allergens like pollen, pet dander, and dust may be harder to avoid completely since they can be circulating in the air.

If you do come into contact with an allergen, the best treatment depends on the specific allergy and how severe it is. According to Dr. Schussler, the typical treatment for a mild allergic reaction is an antihistamine, which is an oral medication. However, if you’re having a more severe reaction, an epinephrine shot should be used promptly. Epinephrine is an emergency injected medication that relaxes airway muscles and constricts blood vessels during a severe allergic reaction.

Long-term allergic reactions can be prevented and managed with maintenance medications that either block other chemicals released during an allergic reaction (leukotriene modifiers) or desensitize you to the allergen itself (immunotherapy). People with allergies to things like pet dander, pollen, dust, and other environmental allergens, may need to take over-the-counter (OTC) or prescription medications regularly to help control their symptoms.

Here’s a breakdown of the most common OTC and prescription allergy medications:

  • Antihistamines: One of the most common allergy medications, antihistamines, block histamine, a symptom-causing chemical released by your immune system during an allergic reaction. They are commonly used to treat allergies such as allergic rhinitis or urticaria (hives). Antihistamine medications are available by prescription and OTC as pills, liquid, nasal sprays, or eye drops. They help ease itchy or runny nose, itchy or watery eyes, hives, swelling, sinus congestion, and postnasal drip. You can find medications like cetirizine (Zyrtec), fexofenadine (Allegra), and loratadine (Claritin) at your local pharmacy.
  • Decongestants: Decongestants provide quick, temporary relief to symptoms related to allergies, such as inflammation, swelling, and mucus production that can occur in the nose. They are available by prescription and OTC as pills, liquid, nasal sprays, or drops.3 A few examples include oxymetazoline (Afrin, Dristan, Vicks Sinex), phenylephrine, (Sudafed PE and Suphedrin PE), and pseudoephedrine (Silfedrine, Sudafed, and Suphedrin).
  • Corticosteroids: Your doctor may prescribe corticosteroids for severe reactions, especially when antihistamine and decongestant medication fails to relieve allergy symptoms. They are available OTC and by prescription as pills, liquid, nasal sprays, inhalers, creams, or eye drops. Corticosteroids help ease an itchy or runny nose, itchy or watery eyes, hives, swelling, sinus congestion, and postnasal drip, according to the AAFA. Inhaled corticosteroids help with allergic asthma symptoms.
  • Leukotriene modifiers: Leukotriene modifiers treat asthma and nasal allergy symptoms such as nasal congestion, runny nose, and sneezing, along with wheezing and shortness of breath, according to the Cleveland Clinic. Leukotriene modifiers are only available by prescription and come in pills, chewable tablets, and oral granules (small pieces that dissolve into food and drink). There are three available medications, but only montelukast (Singulair) is approved to treat allergic rhinitis in addition to allergic asthma.
  • Allergy immunotherapy: Both sublingual immunotherapy (SLIT) and allergy shots are used to train the body’s immune system not to react to allergens, per the ACAAI. Allergy shots can be given initially as a series of weekly injections, followed by a maintenance schedule. Sublingual therapy is another form of allergy immunotherapy and involves administering an allergen-based tablet under the tongue, generally on a daily basis.
  • Epinephrine shots: In the event of a severe life-threatening reaction called anaphylaxis, self-injecting epinephrine shots are used to reduce symptoms. Epinephrine is often used if you accidentally eat a food you are allergic to and have a severe reaction. Also, if you’re exposed to a trigger that caused an allergic reaction in the past, you can use epinephrine before symptoms develop. For example, you can use an epinephrine auto-injector (EpiPen, Auvi-Q) immediately following a bee sting to help ward off potentially dangerous symptoms.

It’s important to note that children need different doses of medication than adults, and in some cases, an entirely different medication, according to the U.S. Food and Drug Administration. So, always consult your physician when it comes to using over-the-counter treatments for children.

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What is anaphylaxis and what should you do in an emergency?

For many people, allergies are just a nuisance that often gets better by avoiding the allergen, taking OTC or prescription medications, or making lifestyle modifications. However, there are times when an allergic reaction becomes an emergency that requires immediate medical attention. Anaphylaxis is a sudden, life-threatening allergic reaction involving several areas of the body, including the skin, respiratory system, cardiovascular system, and G.I. tract.5

Anaphylaxis requires a quick and immediate reaction, which means you need to know what to do if it happens to you or a loved one. “Symptoms develop fast, about five to 30 minutes after exposure to an allergen, though in some cases it can be as long as a few hours,” Dr. Schussler says. According to the Mayo Clinic, signs and symptoms of anaphylaxis can be serious and include:

  • Low blood pressure
  • Skin reactions like rash, itching, or hives
  • Swollen tongue or throat
  • Wheezing or trouble breathing
  • Weak or rapid pulse
  • Dizziness or fainting
  • Nausea or vomiting
  • Diarrhea

Timing is crucial when treating anaphylaxis. If this is a new reaction or you do not have access to an epinephrine auto-injector, call 911 or go to the emergency room immediately. If you carry epinephrine, administer it right away, says Dr. Schlussler. Even if symptoms improve after the injection, you still need to seek emergency medical attention for additional monitoring and to avoid a second reaction.

Depending on the symptoms, you may also need oxygen to help with breathing, I.V. antihistamines and cortisone to reduce inflammation and improve breathing, or a beta-agonist like albuterol to relieve breathing symptoms, per the Mayo Clinic. In severe cases, CPR may be necessary.

As to what causes anaphylaxis, Dr. Schussler says the most common triggers are foods, medications, and insect venom, with food being the most common reason people go to the E.R. for anaphylaxis. There is also evidence to suggest that allergic conditions are becoming more common in the U.S.: One 2020 study published in the The Journal of Allergy and Clinical Immunology: In Practice found that allergy-related E.R. visits jumped 14% from 2007 to 2015.6

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What can you do in your daily life to avoid allergic reactions?

Allergic reactions can wreak havoc on your body and cause disruptions in your routine. If itchy eyes and an ever-present tickle in your nose aren’t on your agenda, there are things you can do to avoid allergic reactions from happening in the first place.

The best thing you can do is avoid the culprit. That’s often easier to do with things like food or latex allergies, but for non-food-related allergies like pollen, insect bites, pets, and mold, this means you need to stay clear of those allergens by avoiding skin contact and inhalation, if possible.

How can you do this? Staying indoors when pollen counts are high and minimizing contact with pets can help decrease a reaction. If you’re allergic to insect bites, keep your epinephrine auto-injector with you always. And if you do come into contact with an allergen, take any OTC drugs or medications prescribed by your doctor.

If you have a food allergy, it’s critical— and potentially life-saving—to avoid the ingredient and any product containing it. This requires reading food labels and knowing alternate names for allergic foods. For example, egg, ovalbumin, and ovomucoid are all names for egg allergens. Your doctor may ask you to keep a food diary to note any reactions to specific food allergens. And most importantly, if you have a food allergy that can result in anaphylaxis, keep your epinephrine auto-injector on you at all times. You may also want to consider wearing a medical alert bracelet or necklace with your name and allergy information, especially for life-threatening allergies.

Dealing with allergies generally falls into the “no fun” category, but with the right treatment plan and support, you can learn to manage allergic reactions when they occur and prevent future ones from taking place.

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  1. StatPearls, Allergy
  2. StatPeals, Type I Hypersensitivity Reaction
  3. StatPearls, Allergic Rhinitis
  4. StatPearls, Allergic Conjunctivitis
  5. StatPearls, Food Allergies
  6. StatPearls, Anaphylaxis
  7. The Journal of Allergy and Clinical Immunology: In Practice: Increasing Allergy-Related Emergency Department Visits in the United States, 2007 to 2015

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