The K Health Guide to Allergies

By Chris Bodle, MD
Medically reviewed checkmarkMedically reviewed
March 17, 2020

Allergies are one of the most common causes of chronic illness in the United States, affecting more than 50 million Americans each year. Allergies are triggered when the body’s immune system mistakenly reacts to a particular substance (called an allergen) as an invader and overproduces antibodies to attack that allergen, causing an allergic reaction.

The severity of allergic reactions ranges from person to person. For some people, allergies create a mild inconvenience in their day-to-day life, while for others, allergies can be life-threatening.

Although allergies cannot be “cured,” living comfortably with most allergies is possible thanks to modern treatments that can prevent or mitigate symptoms. When allergies are properly managed, most people experience little disruption to their lives, other than minor, occasional irritation. Some people will need to carry medication at all times should they encounter their allergen, and, in rarer cases, people with severe allergies must avoid encountering their allergens altogether.

In this guide to allergies, I’ll cover the following:

What Are Allergies?

Put simply, an allergy is your immune system overreacting to a foreign substance that would otherwise be harmless.

Our immune systems are responsible for defending our bodies from foreign substances, also known as antigens. Some antigens are dangerous to our health, such as certain viruses or bacteria; others are relatively harmless, such as cat dander, gluten, or pollen.

Dangerous or not, when your immune system detects antigens in your body, it produces antibodies called immunoglobulins to attack the foreign substance and destroy it. In a non-allergic person, the process of destroying antigens happens without any noticeable effects. In an allergic person, however, the immune system overreacts to a specific foreign substance by creating large quantities of immunoglobulin E (IgE). The IgE attaches itself to other cells in the body and initiates reactions that cause the symptoms of an allergic reaction.

If you suffer from cat allergies, for example, your immune system mistakenly reacts to a cat’s dander as if it were a dangerous parasite that may harm your body—and attacks it accordingly. As a result, you feel the uncomfortable symptoms of your body trying to rid itself of the “invader,” which may present as a raised red rash (hives), itchiness, watery eyes, or a number of other reactions.

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Common Types of Allergies

A wide variety of everyday substances can cause allergic reactions, and it’s common for people to be allergic to more than one substance. If you have allergies, you may react to eating certain foods, touching a particular material, or encountering a specific animal.

Here are some common types of allergies:

Food allergy

The body can be allergic to a wide range of foods and ingredients including peanuts, gluten, soy, fruits, shellfish, and proteins in dairy products. This type of allergy is usually triggered by consuming the food, though in some cases simply touching or coming into contact with the food can trigger a reaction. (Note that a gluten allergy is different from celiac disease, which is an autoimmune condition, though they can result in similar symptoms.)

Pet allergy

As the two most popular pets in the United States, cat and dog allergies are fairly common, with cat allergies being twice as common as dog allergies. In these cases, the body is generally triggered by proteins in the animal’s urine, saliva, or dander. If you have pet allergies, you may find yourself less sensitive to certain breeds of dogs or cats, but there is no such thing as an entirely “hypoallergenic’’ breed.


Seasonal allergies may flare up in spring, summer, or early fall, thanks to pollen from trees, flowers, and other plants. However, some people suffer from perennial allergies to pollen that affect them all year round.

Insect allergy

The sting of insects, like bees and wasps, the bite of an insect (e.g. mosquito bite allergies), or being in close proximity to certain pests, like dust mites, may trigger allergic reactions.

Latex allergy

A small number of people suffer from latex allergies, triggered by touching or handling products made with latex. Latex allergies are more prevalent among health care workers, as their jobs require the frequent use of latex gloves. If you’re allergic to latex, you may also need to avoid certain foods that contain proteins similar to those in the tree sap that latex is made from.

Mold allergy

If you have a mold allergy, it can be triggered by breathing in mold spores, commonly found in homes, buildings, and in places with lots of moisture.

Drug allergy

Medications such as penicillin, aspirin, ibuprofen, naproxen, or ingredients in local anesthetics can trigger allergic reactions. If you have a drug allergy, it’s important to notify all of your doctors and wear a medical alert bracelet to inform health care professionals in the event you are brought into an emergency room.

Allergy Symptoms

Allergy symptoms run the gamut, ranging from mild nuisance to potentially fatal if not addressed immediately. Different people can react differently to the same allergen, and some symptoms, such as eye allergies, may present as fairly mild in one person and intense in another.

Allergies can even trigger asthma (known as allergy-induced asthma) or exacerbate symptoms in people who already have asthma.

Common allergy symptoms include:


While many common allergy symptoms have similarities to the common cold, there are also more dangerous symptoms that can cause serious harm. The most dangerous form of an allergic reaction is anaphylaxis, a life-threatening reaction in which the body goes into shock, requiring emergency medical attention. This severe reaction is found with allergies to many substances including insects, foods, medications, and latex.

Anaphylaxis symptoms include:

Many doctors will require people who are at risk of severe allergic reactions to carry an epinephrine auto-injector, with them at all times. Epinephrine auto-injectors can be prescribed by your doctor, are self-administered, and work by injecting a dose of this potentially life saving medication into your body. It can essentially reverse the effects of anaphylaxis.

If you or someone in your presence is experiencing anaphylaxis, call 911 and seek emergency medical care. If available, you should use an epinephrine auto-injector by pressing it into the thigh. Whether or not an epinephrine auto-injector was used, a visit to the emergency room for follow up treatment is the important next step.

What Causes Allergies?

You can develop allergies at any age, from birth through adulthood. Health professionals are still uncertain of what causes allergies in some people and not in others, but we do know that both the environment and genetics play a role in the development of allergies.

If you have a family history of allergies and if you have asthma, you’re at a higher risk of developing allergies. If you have an existing allergy, you’re also more likely to develop other allergies. In newborns, some research suggests that birth by Caesarean section (C-section) may create a higher likelihood of developing allergies.

It’s also possible to outgrow allergies over time, with the allergic reaction decreasing or disappearing entirely on its own.

Diagnosing Allergies

To diagnose allergies, your doctor will examine your medical history, perform a physical exam, and conduct one or more allergy tests to identify particular allergens.

There are four methods of allergy testing:

  • Skin test: Your doctor will place a small amount of the suspected allergen on your skin and then break the skin. If the skin around the region shows swelling, this indicates you are allergic to the substance. This is the most efficient and common form of allergy testing, as it can show results within minutes.
  • Intradermal test: If a skin test is inconclusive, your doctor may turn to an intradermal test. The doctor will inject some of the suspected allergen into your skin via a syringe and then watch for a similar swelling reaction to indicate an allergy.
  • Blood test: In some cases, your doctor may recommend a blood test to accurately identify an allergy. This requires having your blood drawn, where it is tested for specific antibodies in a lab.
  • Challenge test: If your doctor suspects you may have a food or drug allergy, they may ask you to consume a very small amount of the suspected food or drug while the doctor closely monitors your symptoms. Only attempt this test under the close watch of your doctor or allergist.

Allergy Treatment

Treatment for an allergic reaction will differ depending on the severity of your symptoms. While most people suffering from allergies use short-term treatments, which are intended to provide immediate relief during an allergic reaction, there are also some long-term treatments aimed at gradually decreasing your overall allergic reactions and symptoms.

For mild allergy symptoms, short-term treatment can include over-the-counter (OTC) allergy medicine, like antihistamines, or cold and flu medications to alleviate symptoms such as congestion, watery eyes, and itchy throat.

Treatment for allergies that affect the eyes may include eye drops to relieve irritation and wash allergens from the eye. In cases of chronic eye allergies, your doctor may recommend corticosteroids (steroid eye drops) for stronger relief.

In the case of a serious allergic reaction that involves trouble breathing or anaphylaxis, you should always call 911 and, if available, use an epinephrine auto-injector immediately. Whether you have an epinephrine on hand or not, if you experience anaphylaxis, you need to go to the emergency room for follow-up treatment.

The most common form of long-term allergy treatment is allergen immunotherapy, otherwise known as allergy shots. This method is intended to reduce your sensitivity to the allergen over time, therefore easing future symptoms. Similar to getting a vaccine, allergy shots work by injecting very small amounts of the allergen into your body and gradually increasing the dosage over time to help your body develop its own immunity or tolerance to the substance.

While some people experience a lasting reduction in their allergies after allergy shot treatment, others see only temporary relief and may revert back to their former symptoms after treatment ends. Ask your doctor if you are curious whether allergen immunotherapy is right for you.

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Allergy Prevention

The best way to prevent allergy symptoms is to avoid any known allergen(s) entirely. If you have a food allergy, this is the common method of prevention. By cutting the allergen food out of your diet, you’ll have almost no risk of experiencing an allergic reaction.

Sometimes, it’s impossible to avoid your allergen. In these cases, like with pollen allergies, the approach is to provide allergy relief, rather than prevent it altogether.

For severe allergic reactions where there is a risk of anaphylaxis, you should carry an epinephrine auto-injector (such as EpiPen or Auvi-Q). It’s also a good idea to wear a medical alert bracelet or necklace to inform medical personnel and others that you have a serious allergy. This can be life-saving if you are ever having a health emergency in which you’re not able to speak.

In all cases, prevention requires that you be mindful and aware of your surroundings, often going out of your way to monitor for the presence of your allergens.

When to See a Doctor

If you have a serious allergy, it usually becomes clear upon having your first allergic reaction to the allergen. If you experience swelling in your mouth or throat, trouble breathing, lightheadedness, or severe hives and skin irritation after consuming food, taking medication, or touching a certain material, contact your doctor as soon as possible. It’s important to be tested to confirm your allergy and get an epinephrine auto-injector if necessary.

For more mild allergies, it can be difficult to tell the difference between allergies and a cold or indigestion, as many of the symptoms feel the same. Speak with your doctor about potential allergies if you experience:

  • A pattern of cold-like or skin irritation symptoms (runny nose, watery eyes, sneezing, hives) when you are in contact with a specific animal, plant, food, medicine, or material.
  • Cold symptoms when you are in a particular environment, such as inside your home or at your office, that seem to disappear as soon as you are out of that environment.
  • A pattern of serious stomach cramping, diarrhea, or vomiting after eating, drinking, or taking medication.

How K Health Can Help

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K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Chris Bodle, MD

Dr. Bodle is a board certified emergency medicine physician. He received his medical degree from Indiana University School of Medicine, and completed his residency in emergency medicine at Emory University. In addition to K Health, he currently works as an Emergency Medicine physician in an Urban, Level 1 Trauma Center in the south east.