Allergies - overview

Allergy - allergies; Allergy - allergens

An allergy is an immune response or reaction to substances that are usually not harmful.

Allergic reactions

Allergic reaction can be provoked by skin contact with poison plants, chemicals and animal scratches, as well as by insect stings. Ingesting or inhaling substances like pollen, animal dander, molds and mildew, dust, nuts and shellfish, may also cause allergic reaction. Medications such as penicillin and other antibiotics are also to be taken with care, to assure an allergic reflex is not triggered.

Allergy symptoms

The immune system normally responds to harmful substances such as bacteria, viruses and toxins by producing symptoms such as runny nose and congestion, post-nasal drip and sore throat, and itchy ears and eyes. An allergic reaction can produce the same symptoms in response to substances that are generally harmless, like dust, dander or pollen. The sensitized immune system produces antibodies to these allergens, which cause chemicals called histamines to be released into the bloodstream, causing itching, swelling of affected tissues, mucus production, hives, rashes, and other symptoms. Symptoms vary in severity from person to person.

Histamine is released

Mast cells release histamine when an allergen is encountered. The histamine response can produce sneezing, itching, hives and watery eyes.

Introduction to allergy treatment

Treatment varies with the severity and type of allergy symptom. The first course of action is to avoid the allergen if possible. Medications such as antihistamines are then usually prescribed to relieve the allergic symptoms. Immunotherapy, or allergy shots, is occasionally recommended if the allergen cannot be avoided. It includes regular injections of the allergen, given in increasing doses that may de-sensitize the body to the allergen.

Hives (urticaria) on the arm

Hives (urticaria) are raised, red, itchy welts, seen here on the arm. The majority of urticaria develop as a result of allergic reactions. Occasionally, they may be associated with autoimmune diseases, infections (parasitosis), drugs, malignancy, or other causes.

Hives (urticaria) on the chest

Hives (urticaria) are raised, red, itchy welts, seen here on the chest. The majority of urticaria develop as a result of allergic reactions. Occasionally they may be associated with autoimmune diseases, infections (parasitosis), drugs, malignancy, or other causes.


Heredity, environmental conditions, number and type of exposures and emotional factors can indicate a predisposition to allergies.


Antigens are large molecules (usually proteins) on the surface of cells, viruses, fungi, bacteria, and some non-living substances such as toxins, chemicals, drugs, and foreign particles. The immune system recognizes antigens and produces antibodies that destroy substances containing antigens.

Blooming flowers and blossoming trees are signs that spring has arrived. But for some people, those blossoms and blooms are also signs that allergy season is under way. And that means months of sniffling, sneezing, and runny eyes ahead. You may know that you have allergies as soon as you step outside on a spring day, eat peanuts, or pet your dog. Signs of an allergy may include trouble breathing, teary eyes, hives, itching, or vomiting after you come in contact with your allergy trigger. Your doctor can also do allergy tests to find out whether you're allergic, and what triggers your allergies. The most common type of allergy test is a skin test. The doctor puts a small amount of different allergy-causing substances under your skin. Then you wait for signs of a reaction, like swelling or redness. You might also have blood tests to check for chemicals that are related to allergies. So, how are allergies treated? There are a few medicines you can buy at your local drugstore or your doctor can prescribe to treat your allergies. Antihistamines prevent histamine chemicals from triggering allergy symptoms. Decongestants shrink swollen blood vessels throughout your body, including inside your nose, perhaps helping you breathe easier. Steroid drugs reduce swelling and inflammation. And Leukotriene inhibitors block the substances that trigger allergies. If your allergy is really bugging you, your doctor may give you allergy shots. When you take allergy shots over time, eventually they can help your body get used to the substance so you don't over-react to it in the future. Usually you can relieve allergies by taking medicine and avoiding whatever it is that triggers them. But in some people, allergies to insect stings or certain foods, like peanuts, cause a life-threatening reaction. This is called anaphylaxis. And if you have a life-threatening allergic reaction, call immediately for emergency medical help.



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