Information About Allergies

Common Allergy Terms

Allergic conjunctivitis:  An allergic reaction of the eyes.  The whites of the eyes (conjunctivae) become red and itchy, and an excessive amount of tears are produced.

Allergic contact dermatitis: An allergic reaction of the skin.  The skin becomes red, itchy, weepy and bumpy wherever it has come into contact with a substance that the immune system recognizes as foreign, such as poison ivy.   The rash usually starts out in streaks or patches, corresponding to where the foreign substance has touched the skin.  It may spread out beyond those locations with time.  Typically the same bumps of this rash will last days or weeks.

Allergic rhinitis:  An allergic reaction of the nose, having some similarity to a cold.  Symptoms include nasal congestion, a clear runny nose, sneezing and itching. Post-nasal dripping of clear mucus frequently causes a cough. Loss of smell is common and loss of taste occurs occasionally. Nose bleeding may occur if the condition is severe. Allergic conjunctivitis (eye itching, redness, and tearing) frequently accompanies the nasal symptoms.

Allergist:  A physician who specializes in treating allergies.  The highest level of training and certification is administered by the American Board of Allergy and Immunology.  In order to be board-certified, a physician must first complete training (“residency”) in either Pediatrics or Internal Medicine (adult medicine).  Those trainings take at least three years.  The doctor then trains for an additional two years in an approved Allergy and Immunology fellowship.  This is followed by a rigorous examination.

Allergy:  An allergy is the ability to have a harmful immune reaction to a foreign substance.  Several points are worth noting:

  • Your body injures itself as part of the response to the foreign substance.
  • The foreign material may be harmless by itself.  It is not a poison.
  • Allergies may involve different parts of the body, like the nose (hay fever) or lungs (asthma).
  • You have the allergy (the abnormal sensitivity) all the time, but may feel absolutely normal if you are not being exposed to the offending substance.

Allergen:  A substance that can cause an allergic reaction in some people.  Examples would include pollen, dust, mold and dander.

Allergy level:  See pollen count

Allergy report: See pollen count

Anaphylaxis:  A severe allergic reaction involving the entire body.  This may include hives, wheezing, a drop in blood pressure and sometimes death.  Immediate treatment is required.

Antibody: A specialized protein, produced by the immune system in response to a substance, labeled the allergen, which looks foreign or undesirable to the body.  The antibody binds to the allergen and coordinates the allergen’s destruction.

Antihistamine:  A medication which blocks the effects of histamine.  When you have an allergic reaction, you most typically release histamine and other chemicals, which cause itching, swelling and other problems.

Asthma:  A common disorder of the lungs involving irritation (inflammation) of the tubes which carry air in and out of the lungs, known as airways or bronchi and broncioles. This irritation results in swelling of the walls of the airways and excess mucus production.  Also, muscle fibers in the walls of the airways become irritated and contract.  The swelling and muscle contraction causes narrowing of the airways.  This makes it harder to breathe and causes air to whistle through the lungs, known as wheezing.  The excess mucus production leads to coughing. Much but not all asthma is allergic in origin.  Knowing what you’re allergic to is an important part of dealing effectively with asthma.

Atopic:  A medical term meaning “allergic”.  A person who has allergies is atopic.

Atopic dermatitis:  A skin disease characterized by itching, redness, bumpiness, and scaling.  Another name for this disorder is eczema.  Attacks of atopic dermatitis can last for weeks, months, or be more or less continuous for years.  Atopic dermatitis appears in different patterns, including generalized, whole-body rash in the very young and flexural, which occurs in the folds of the elbows and knees in older children and adults.  The cause of atopic dermatitis is not known, although it appears to have some link to allergy.   Often allergic factors can be identified which trigger a worsening of atopic dermatitis.

Bee sting allergy:  See insect sting allergy.

Cedar fever:  A common term for allergy to “mountain cedar”, a type of juniper found in central Texas and neighboring areas.  Mountain cedar is the main cause of winter allergies in Austin, although increased house dust exposure from cleaning and decorating for the holidays can also be a factor.

By the way, many common allergic reactions are often called “fever”, even though they don’t actually cause an increase in your temperature!  This includes cedar fever, hay fever (ragweed in the United States), rose fever (grass), and others.  If you truly have a fever, you probably have an infection on top of your allergies!

Congestion:  A surprisingly confusing term.  When an allergist uses the term, he most often is talking about “nasal congestion”, meaning that the inside of your nose is swollen, making it hard to breathe and forcing you to breathe through your mouth.  People sometimes use the term “congestion” to mean excessive mucus coming from the nose.  “Chest congestion” is often used to mean some mixture of coughing and/or shortness of breath.

Contact dermatitis: A rash caused by contact between skin and some substance.  Possible causes include allergic contact dermatitis (see above) and irritant contact dermatitis.  An example of irritant contact dermatitis would be “dish pan hands” brought on by repeated contact with water and soap, which directly injure the skin.

Dander:  Tiny scales shed from skin or hair.  Animal dander can cause allergic reactions in susceptible people.  For example, cat dander consists of the mixture of oils and protein which coat the hairs as they grow out of the skin, along with dried saliva from licking and bits of dried urine.  The cat proteins are the ingredients to which a person may be allergic.  Animal dander is very light, and can float in the air for a long time.  It is a major component of household dust.

Diagnosis:  This term has two related definitions.  The first is the recognition of a disease by its symptoms and outward signs.  The second is the analysis of the underlying cause of a disease.

Dust:  Obviously, many things can be floating in the air as tiny particles (dust), and some of them can cause allergic reactions.

When an allergist talks about dust allergy, he is most often talking about allergy to indoor house dust, specifically to house dust mites (see below).  Other things, including animal dander, mold, and pollen from outdoors can be found in indoor dust.

Outdoor dust, such as you would experience on a windy day or cutting the lawn, consists of pollen and mold, from an allergy point of view.  It also contains sand, pieces of plants and other things which may be irritating to respiratory tract, but which do not cause an allergic reaction.

Dust mite:  See house dust mite.

Eczema:  See atopic dermatitis.

Food allergy:  An unpleasant or unhealthy reaction to a food is a common experience.  Not all reactions to food, however, are allergic. For a reaction to qualify as a food allergy, it must involve overreaction by the immune system.  For example, in a true allergy to milk, the body reacts violently to milk protein.  Symptoms may include vomiting, hives and wheezing.
Other common causes of food allergies include eggs, wheat, peanut, soybean, tree nuts, fish and shellfish.  It is estimated that six to eight percent of children under the age of three and nearly four percent of adults have food allergies, and the incidence is rising.

Nonallergic reactions to food are also common.  Lactose intolerance, caused by the inability to digest the sugar in milk, is a well-known example.  In lactose intolerance, the sugar in milk makes it all the way to the colon, where bacteria consume it, produce carbon dioxide (gas) as a byproduct, and cause abdominal cramping and diarrhea.  Another common nonallergic adverse food reaction is food poisoning, where food contaminated with harmful bacteria is eaten.  Toxic reactions, such as consuming too much caffeine, are another type of a nonallergic adverse food reaction.

Sometimes it is not immediately obvious what food, if any, you are reacting to, and whether that food reaction is truly an allergy.  This is a situation where the thorough questioning and tests of an allergist can help.

Fungus:  A fungus is a type of organism that lives by consuming other organisms.  Fungi are responsible for the majority of decomposing or “recycling” of dead material.  They are as essential to the continuation of life as plants and animals.  Most fungi are microscopic, although some, such as mushrooms, are easily visible.

Different fungi have different favorite growing conditions.  Changes in available food source, temperature and humidity all influence which fungi are found in the atmosphere at a given time of year.  Some thrive on hay or tomatoes.  Others prefer the sheltered environment inside our homes.  Some, such as the yeasts which produce bread, beer and wine, are an integral part of our everyday life.

Fungi are a common cause of allergic reactions.  The wind can easily pick up individual fungi and their spores and carry them for miles, until they are inhaled by a sensitive individual.

Gluten:  The protein found in wheat and some other grains.  Gluten may cause an immediate allergic reaction in sensitive persons, with nausea, vomiting, hives and signs of anaphylaxis.  More often, gluten causes a somewhat slower but still significant reaction called celiac disease.  In celiac disease, an adverse reaction by a different branch of the immune system strips off the lining of the intestines, leading to diarrhea, abdominal cramping, and a variety of other symptoms.

Hay fever:  Allergic rhinitis due to pollen.  See allergic rhinitis.  Hay fever was originally named as the nose and eye problems occurring during hay harvesting time in the early summer.  We now know that grass pollen goes through the air at that time.  Today we have expanded the use of the term hay fever to mean allergic rhinitis caused by pollen at any time of year.

Histamine:  A chemical that plays a major role in many allergic reactions.  Histamine causes blood vessels to relax, expand and leak fluid.

Hives:  Raised, itchy areas of skin.  The swelling will usually come and go in a matter of a few hours.  Some severe hives can be present for several days, often with bruising.  A large percentage of people will experience hives at some point in their lives.  Some hives are caused by allergic reactions.  Others may be triggered by an infection.  In many cases, the true cause of hives is difficult to identify.

House dust mite:  Dust mites are the primary cause of allergies related to house dust.  They are tiny (a few tenths on a millimeter long) creatures with eight legs, related to spiders.  There are several types of house dust mites; two of them are predominant in Central Texas, Dermatophagoides farinae and Dermatophagoides pteronyssinus.  They are found wherever people live.  Their absolutely essential food is tiny bits of human skin.  (No, that itch on your arm is not a dust mite biting you!)  Dust mites also need warmth and humidity.  If you are allergic to house dust mites, understanding how to minimize their numbers is an important part of your treatment.

Immune: Protected against infection.

Immune response: Any reaction by the immune system.

Immune system: A complex system that is responsible for distinguishing us from everything foreign to us, and for protecting us against infections and foreign substances. The immune system works to seek and kill invaders.

Immunoglobulin:  An alternative medical term for Antibody.  Immunoglobulins come in five different classes, termed immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), immunoglobulin D (IgD) and immunoglobulin E (IgE).

Immunoglobulin E: Abbreviated IgE. The type of antibody involved in allergic reactions.

Insect sting allergy:  Honey bees, wasps, hornets, yellow jackets, and fire ants are related.  Their venoms can cause allergic reactions.  Testing is available for allergy to their venoms, and immunotherapy injections (allergy shots) can dramatically decrease sensitivity.

Latex:  The milky sap from a plant, which is used to make rubber.  The term is derived from the Spanish word leche, meaning milk.  Most often, rubber is made from the latex of the tree Hevea brasiliensis

Lower respiratory tract infection:  An infection of the lungs.  Examples include pneumonia, bronchitis, and lung abscess.

Milk allergy:  An adverse reaction to the protein in milk which involves the immune system. This may involve respiratory (allergic rhinitis, allergic asthma), dermatologic (hives, eczema or other skin problems), gastrointestinal (nausea, vomiting, diarrhea, constipation, colic) and systemic (shock) symptoms.  Symptoms may begin minutes to hours after exposure.

True milk allergy needs to be differentiated from lactose intolerance.  Lactose intolerance, the inability to digest milk sugar, is a common condition which affects most non-Caucasian people beyond infancy.  It results in diarrhea and abdominal discomfort.

A person who is truly allergic to milk needs to avoid foods which are labeled as containing whey, casein, caseinate, or natural butter flavor.

Mite: A tiny eight-legged creature, related to spiders and ticks. Some mites live freely and others as parasites. House dust mites are a common cause of allergy.  Grain storage mites are occasionally reported to cause severe reactions.

Mold: A microscopic fungus that lives on plant or animal matter. Most molds are filamentous and produce spores.  They are a common cause of allergy.

Peanut allergy:  An adverse reaction to peanut protein, mediated by the immune system.  Peanut allergy is the most common cause of fatal food reaction.

Poison ivy allergy: A common example of allergic contact dermatitis, due to reaction to the sap of poison ivy or one of its relatives.  The official Latin name for poison ivy and its close relatives is Rhus, so you may see mention of Rhus dermatitis.

Pollen: Small, light, dry protein particles from trees, grasses, flowers, and weeds that may be spread by the wind. Pollen particles are usually the male sex cells of the plant, and are smaller than the tip of a pin. Pollen is a potent stimulator of allergic responses. It lodges in the mucus membranes that line the nose and in other parts of the respiratory tract, causing irritation and histamine reactions.

Pollen count, pollen report, pollen level:  A report of the amount of pollen in the air in a given locality.  A full pollen count will list small or large amounts of many different types of pollen.  Often, mold particles are also counted.
When you see a pollen count in the media, usually only one or a few major types of pollen are listed, based upon the season.  All of the various types of molds are commonly lumped together into one count, much like the Dow Jones Report adds up a number of stocks.

Pollen counts are most commonly given in particles per cubic meter of air.  Numeric ranges for low, medium and high counts are determined based on expected symptoms.  A low count will cause symptoms in only a few highly sensitive people.  A high count would bring on symptoms in virtually all people allergic to a given pollen.

Respiratory infection:  Please see upper respiratory tract infection or lower respiratory tract infection

Rhinitis:  Irritation and inflammation of the internal surface of the nose.  The primary symptoms of rhinitis include runny nose, postnasal drip, congestion, sneezing and itching.  In the United States, more than 50 million Americans currently suffer from allergies.

Rhinorrhea:  The medical term for runny nose..

Sensitive:  This term is commonly used interchangeably with ”allergic”.

Shock:  A critical condition brought on by a sudden drop in blood flow through the body. This sharply decreases the delivery of oxygen and nutrients to vital organs. It also compromises the kidneys and so curtails the removal of wastes from the body. Shock can be due to a number of different mechanisms including not enough blood volume and not enough output of blood by the heart.  Allergic shock (anaphylaxis) is a type of shock brought on by excessive relaxation of the blood vessels, and thus resembles low blood volume.

Sinus:  The sinuses are air-filled spaces in the head, connected to the nasal cavity.  Since they are next to the nose, they are more properly called paranasal sinuses.  There are several types of paranasal sinuses:

  •     Maxillary sinuses are large and under the eyes.
  •     Frontal sinuses are above the eyes.
  •     Ethmoid sinuses are like a cluster of small grapes, behind the upper nose, between the eyes.
  •     Sphenoid sinuses are near the center of the skull, behind the roof of the mouth.

Sometimes, when a person says that he has “sinus”, he means either that he has pain in a sinus or else infection in a sinus, more properly termed “Sinusitis”.

Sinusitis, sinus infection:  Infection of the paranasal sinuses.  This may be caused by bacteria, viruses or fungi.  Sometimes the term rhinosinusitis is used, since the infection usually also involves the nose.

Sinus infection often causes pain:

  •     Maxillary sinusitis causes pain or pressure in the cheeks and in the upper teeth.
  •     Frontal sinusitis causes pain or pressure in the forehead above the eyes.
  •     Ethmoid sinusitis causes pain or pressure between or behind the eyes or at the back of the neck.
  •     Sphenoid sinusitis causes pain or pressure behind the eyes or at the vertex (top of the head).

Soy allergy:  An allergic reaction to the protein of soybean.  Soybean is one of the more common causes of food allergy.  It can be difficult to diagnose because soy is often an ingredient in foods in restaurants or that are prepackaged.  Other words used to denote soy include soya, shoyu, tempeh, miso, natto, edamame, tofu, vegetable protein, vegetable broth, vegetable broth, vegetable gum, vegetable starch, and flavoring.

Upper respiratory tract infection:  An infection of the nose, sinuses, pharynx and/or larynx.  Common examples include colds and sinus infections.

Urticaria:  The technical name for hives

Wheat allergy:  See gluten

Wheeze:  A whistling noise in the chest during breathing caused by narrowing of the airways.  Wheezing is a frequent sign of asthma.  Other lung diseases may sometimes cause wheezing.