Allergies are an abnormal immune system response against normally harmless substances called allergens, which include things like pollens, dust mites, and molds. The allergic person’s body reacts to allergens by releasing chemicals, including histamine and leukotrienes, that affect the skin, respiratory system, digestive tract, and more. These chemicals ultimately produce symptoms such as sneezing, runny nose, congestion, rash, and swelling.
In some cases, allergies can even lead to life-threatening symptoms, such as anaphylaxis. The most common types of allergies include hay fever, asthma, food allergies, and atopic dermatitis (eczema).
Allergies are among the most common reasons people visit the doctor.
Allergies do not cause fever, though they do cause other symptoms commonly associated with cold and flu, such as runny nose, watery eyes, and sore throat. Though allergic rhinitis is commonly called hay fever, a fever is not one of the symptoms of the condition.
Yes, a cough is commonly associated with asthma, a type of allergic disease. In cough-variant asthma, the primary symptom is a dry, hacking cough that may be worsened by allergic triggers. Cough may also be present with sinusitis, a chronic condition marked by congestion and swelling in the sinuses that often affects people with allergic rhinitis and/or asthma.
Treatment depends on the severity and type of allergic disease you have, but prescription and/or over-the-counter medications may help relieve symptoms.
Allergen immunotherapy, more commonly referred to as allergy shots, is one treatment that can cure some forms of airborne allergies. This treatment is offered by most board-certified allergist-immunologists. Because this treatment can occasionally cause anaphylaxis, these treatments should only be administered in settings where anaphylaxis can be recognized and treated quickly (e.g. allergist's clinic). Anyone interested in allergy shots should see an allergist to undergo allergy testing and to create a personalized treatment plan. Most importantly, people with allergies should do their best to avoid their allergen triggers.
The spring and fall are both considered to be allergy season, but specific timing depends on the type of allergen. Tree pollen is most prevalent in early spring, from January to April, while grass pollen hits its peak between late spring and early summer. From late summer to early fall, weed pollen is the main culprit. However, allergy seasons vary around the world based on climate and the relevant local airborne allergens.
Allergies are caused by an immune system overreaction to a non-threatening trigger. Several different immune mechanisms may be at play, but immunoglobulin E (IgE) hypersensitivity reactions are the main factor behind allergies to insect stings, certain drugs, and foods. Allergies also tend to run in families (atopy), and environmental factors, such as secondhand smoke, can put you at greater risk.
Any substance that triggers an immune system reaction, known as an allergic reaction. Allergens may be airborne (molds, pet dander, pollens), topical (insect stings, latex), or may be certain foods (peanuts, dairy, shellfish), or medications.
A sudden and severe whole-body allergic reaction resulting in a significant drop in blood pressure, the onset of shock, and shortness of breath. Anaphylaxis occurs as the result of an allergy affecting more than one body system at the same time, such as the skin and respiratory systems. Anaphylaxis comes on quickly and is a medical emergency requiring immediate care.
An antibody is a specialized protein created by the immune system in order to defend the body from disease by helping it "recognize" viruses, bacteria, and pathogens by their antigens, which are molecules on their surfaces. Each antibody produced matches a specific antigen, just as a single key fits into a lock. There are four main isotypes, known as immunoglobulins, each with a different role.
Dermatitis is a common skin condition that has many forms. One form, allergic dermatitis (also known as eczema), is an inflammatory skin condition with internal and external triggers. The characteristic symptom is an itchy, red rash.
Also known as allergic rhinitis, hay fever is an inflammation of the nasal passages triggered by an allergen (typically plants, pollens, dust, pets, paint fumes, smoke, etc.). Symptoms include a stuffy/runny nose, sneezing, itchy/watery eyes, cough, sore/itchy throat.
An antibody generated by the B cell lymphocytes of the immune system in response to a threat (allergen). IgE antibodies bind to the allergen and trigger a larger immune response. In some cases, anti-IgE medications can be used in the treatment of allergic diseases such as asthma to block the effects of IgE.
The RAST test is considered an outmoded form of allergy testing, but it used to be a method to detect IgE antibodies in a blood sample. Newer tests, such as ImmunoCAP, involve binding allergenic antibodies in a blood sample to an allergen to measure the antibody quantity. Blood testing is more expensive than skin testing, but in some circumstances can be more convenient and does not require avoidance of antihistamines prior to testing. Blood and skin testing provide similar information.
The most commonly used allergy test, skin testing involves pricking the skin with a tiny drop of an allergen to be tested, then waiting 15 minutes for a skin reaction. A positive allergic reaction in the skin test takes the form of a small, itchy, red bump (hive). Skin testing provides similar information as allergen-specific IgE blood testing.
American Academy of Allergy Asthma & Immunology. Allergic reactions. Updated September 28, 2020.
American Academy of Allergy, Asthma, and Immunology. Allergic reactions. Updated September 28, 2020.
Murrison LB, Brandt EB, Myers JB, Hershey GK. Environmental exposures and mechanisms in allergy and asthma development. The Journal of Clinical Investigation. 2019 Apr 1;129(4):1504-15. doi:10.1172/JCI124612
National Institute of Allergy and Infectious Diseases. Guidelines for the diagnosis and management of food allergy in the United States.
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