Allergies are hypersensitive responses of the immune system to foreign substances. It is a common condition with symptoms that typically include runny nose, watery eyes, sneezing, hives, and rashes; which can usually be managed using over-the-counter medications for symptomatic relief. In life-threatening complications due to an allergic reaction such as anaphylactic shock, patients should use an EpiPen and seek prompt medical attention.

What are Allergies?

Allergies or allergic diseases are the immune system’s reactions to foreign substances encountered in the environment. They form as a result of the hypersensitivity of the immune system against food or environmental allergens that normally do not cause an allergic reaction in everyone. Moreover, the severity of the allergic reaction is also not the same among different people who are allergic to the same substance.

Allergies are highly prevalent with approximately 32 million Americans having some sort of food allergy. This statistic does not include other forms of allergies like pet allergies or pollen allergies. Allergies affect all age groups, including 5.6 million children in the US suffering from food allergies.

What Causes Allergies?

Allergies are caused by foreign substances called allergens that trigger the immune system to produce a hypersensitivity reaction. The immune system, on first exposure to this substance, labels it as a harmful foreign substance. This results in the production of antibodies against the substance that gets activated the next time you get exposed to the same allergen. A second exposure to the allergen causes the antibodies to release several cytokines or chemicals that cause the actual symptoms of allergies.

Certain risk factors increase the likelihood of developing allergies, such as having asthma or having a family history of allergies. Asthma itself is a hypersensitivity condition that can trigger other allergies in affected individuals. Children are considered to be a risk group as they are most likely to have allergies and other allergic conditions.

Common Allergens

Some of the most common allergens include:

  • Peanuts, tree nuts, soy, and shellfish are some of the most common causes of food allergy
  • Pollen, hay, and dust mites are the most common airborne allergens
  • Penicillin and other medications
  • Insect venom and stings, which have a higher likelihood of being fatal
  • Latex

Allergies are most commonly the result of these allergens or a combination of them as it is possible to be allergic to more than one allergen at the same time. However, people can be allergic to anything if the immune system mistakes the substance as a foreign substance during initial exposure.

Common Symptoms

The symptoms of allergic conditions may differ based on the allergen and its route of entry. Generally, allergies affect the sinuses, nasal passages, airways, gastrointestinal system, and skin. Not all symptoms are affected equally by each allergen, with some affecting one system with higher severity than the rest.

General symptoms of an allergic reaction may be mild, moderate, or severe. An allergic reaction causing mild symptoms would cause symptoms that are specific to one part of the body only. These symptoms may include hives, rashes, watery eyes, and a runny nose.

Allergic reactions with moderate symptoms causes can affect multiple parts of the body, such as swelling, breathing difficulties, and itchiness. Hives can also be present during a moderate allergic reaction.

A severe allergic reaction causes the most severe complication of an allergic reaction; Anaphylaxis, a life-threatening emergency as it severely impairs one’s ability to breathe by causing laryngeal edema.

The symptoms of allergic reactions caused by the most common allergens include:

  • Allergic Rhinitis

Allergic rhinitis, or hay fever, is an allergic condition due to exposure to pollen or other environmental allergens. It often presents as sneezing, itchiness of the mucosa, runny or stuffy nose, with symptoms of conjunctivitis (red/itchy or watery eyes).

  • Food Allergy

Food allergies can cause a wide array of symptoms that affect the mouth and throat. It generally causes hives and swelling of the lips, tongue, and throat. Apart from that, food allergy also causes tingling of the mouth and in severe cases, anaphylaxis.

  • Skin Allergy

Skin allergy or atopic dermatitis is a skin condition more commonly known as eczema. The incidence of this condition is quite high with stress and heat as major triggers of an eczema flare-up. It mostly affects the skin with severe itching, excoriations, and flaky skin as the main symptoms.

  • Insect Bite or Sting Allergy

An insect sting can be painful and an allergic reaction only exaggerates that pain. If there is an allergic reaction to the insect sting, the area of the sting will be inflamed and engorged. The allergy can also produce general symptoms of allergy such as itching, hives, and a rash. In severe cases, there may be coughing, tightness of the chest, and even anaphylaxis.

  • Allergic reaction to a medication

Many people are allergic to specific classes of medications and consuming these medications can be life-threatening for them. Within minutes of taking the offending medication, symptoms such as facial swelling, hives, itching, and coughing become apparent. If not treated appropriately, it can lead to an anaphylactic shock.


When an allergic reaction develops, it is important to treat it in a timely and appropriate manner to avoid any complications as they are often life-threatening. Complications of an allergic reaction also include an increased risk of certain conditions due to the over-functioning of the immune system. The most common complications of an allergic reaction are mentioned below:

  • Anaphylaxis

This is the most fatal complication of an allergic reaction as it often sends the human body into shock, affecting multiple organ systems and shutting them down. Anaphylaxis is a severe allergic reaction, often to penicillin, peanuts, and shellfish. It can also occur with insect bites as the venom can also send the body into shock.

An anaphylactic reaction can present with symptoms such as skin rash, difficulty breathing, sudden drop in blood pressure, edema, and swelling of the mouth, eyes, and throat. This swelling is referred to as angioedema for lips and eyes, and laryngeal edema for the throat. Affected individuals may also feel nauseous and dizzy, often resulting in vomiting. Loss of consciousness, coma, and eventually death are other complications of anaphylaxis.

It is important to seek immediate medical help if these symptoms occur as that may help save a person’s life.

  • Asthma

Asthma is a key risk factor for developing allergies, and as it turns out, having allergies increases the risk of developing asthma. This type of asthma is triggered by an allergen and is called allergy-induced asthma.

  • Fungal Infections

The risk of developing a fungal infection of the lungs and sinus is higher amongst those with allergies than those who do not have allergies. The causative pathogen for a fungal lung infection is often Aspergillus fungus, which affects the lungs of an allergic person resulting in allergic bronchopulmonary aspergillosis.

  • Sinusitis infections

As sinuses are most commonly affected by allergic conditions such as asthma and allergic rhinitis, the risk of developing sinusitis is relatively higher in those suffering from these allergic conditions. This is because the sinus is already inflamed and cannot fight off infection like before.


Allergy TestIf someone is suffering from the symptoms of an allergic reaction and over-the-counter medications do not resolve symptoms, it’s important to consult a physician and get diagnosed as they can lead to serious complications.

The diagnosis of an allergic reaction is a long process that requires many tests as physicians and allergists need to determine specific causes of allergy symptoms. The first step for the diagnosis of an allergic condition is to determine whether the symptoms are being produced as a result of an allergy. For this, the physician might ask several questions about the symptoms that are being experienced.

The physician may also require that the patient keep a detailed journal of all symptoms when they occur, and what resolves these symptoms. This helps the physician pinpoint the origin of the symptoms and determine if it’s an allergic reaction. A physical exam may also be performed at this step of the diagnosis.

After it has been determined that it is an allergic reaction, the allergist will focus on assessing the potential triggers and allergens. A detailed journal with details of the foods consumed may help the allergist pinpoint the cause of the food allergy. This will be followed by an exclusion diet where offending foods are excluded and it is observed if there has been any improvement in the symptoms.

For other types of allergies, the physician will order two tests mentioned below:

  • Skin Prick Test

For the purpose f this test, a nurse will prick the patient with small doses of common allergens and the patient will be observed. If hives develop at the site of the prick, then it can be concluded that the patient is allergic to that allergen. However, there may be false positives and false negatives for this test, and a follow-up may be required if the exclusion of the allergen doesn’t resolve the symptoms.

  • Blood Test

A specific type of blood test, namely the radioallergosorbent test (RAST) or ImmunoCAP testing, may be performed to check for the levels of specific IgE in the blood. The IgE is an antibody produced during an allergic reaction, and its levels are tested for diagnosing an allergic reaction.

Medication & Treatment

An allergic reaction cannot be cured but the symptoms can be managed using one of the many over-the-counter medications. Anti-allergic medications target histamine in the blood, which is responsible for the main symptoms of allergies. Allergies can also be managed using other forms of treatment, all of which are mentioned below:

  • Allergen Avoidance

Avoiding the allergen is the easiest way to manage allergies but this method is not effective in treating an ongoing allergic reaction. It is always recommended to avoid allergens, even if the reaction produced is not that significant. This is because a severe allergic reaction may occur at any time. If a person had a mild allergic reaction during the first ten exposures, it is possible to have a severe reaction resulting in anaphylaxis during the eleventh exposure to the same allergen.

  • Medications

Several allergy medications can be used to help manage the symptoms of an allergic reaction. These medications are easily available as over-the-counter medications and they either focus on managing the symptoms such as decongestants like Sudafed and Contact or they can target histamine in the body such as Zyrtec and Allegra. Topical nasal sprays that contain corticosteroids such as Flonase and Nasonex may also be used to improve the symptoms affecting the nasal passages.

If the symptoms of an allergic reaction are severe, a physician may prescribe medication to combat those symptoms. These include medications such as inhaled or oral bronchodilators, inhaled steroids, and even injections of Xolair, Dupixent, and Cinqair. All of these medications are used for the treatment of all types of asthma.

Allergic reactions can also be managed by mast cell stabilizers, which prevent the destruction of mast cells that carry histamine in the bloodstream. It’s the degranulation of these cells that results in an allergic reaction. The most commonly used mast cell stabilizer is cromolyn sodium, which is used intranasally.

  • Saline Irrigation

Saline irrigation is the most helpful in avoiding the development of an allergic reaction by washing off the allergens from the nasal passages. It also helps relieve the symptoms of allergic rhinitis such as postnasal drip and stuffiness of the nose by removing thin mucus that may be present in the nasal passages. It also prevents infections as this method cleans out the bacteria from the nose.

  • Immunotherapy

This form of treatment is considered when there has been no response to other treatment options. It is only for specific patients that suffer from allergy-induced asthma and allergic rhinitis.

  • EpiPen

This is an emergency treatment for severe allergic reactions. An EpiPen contains epinephrine that can reduce the severity of the symptoms till the patient reaches a hospital.


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  • Allergy Facts and Figures