Allergy Glossary of Terms with Definitions on MedicineNet.com

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February 10, 2012

Allergy Glossary of Terms

The following are health and medical definitions of terms that appear in the Allergy article.

Adjacent: Lying nearby. Related terms include superjacent, subjacent, and circumjacent. From ad-, near + the Latin jacere, to lie = to lie near.

Allergen: A substance that is foreign to the body and can cause an allergic reaction in certain people. For examples, pollen, dander, mold.

Allergic conjunctivitis: Inflammation of the whites of the eyes (the conjunctivae) with itching and redness of the eyes and tearing, due to allergy.

Allergic contact dermatitis: A red, itchy, weepy reaction where the skin has come into contact with a substance that the immune system recognizes as foreign, such as poison ivy, poison oak or poison sumac or certain preservatives in creams and lotions. This type of reaction reflects a specific sensitivity or allergy to a specific substance. Also called allergic contact eczema.

Allergic reaction: The hypersensitive response of the immune system of an allergic individual to a substance.
See the entire definition of Allergic reaction

Allergic rhinitis: Medical term for hay fever, a condition due to allergy that mimics a chronic cold. (Hay fever is a misnomer since hay is not a usual cause of this problem and there is no fever. Many substances cause the allergic symptoms in hay fever. Allergic rhinitis is the correct term for this allergic reaction. (Rhinitis means "irritation of the nose" and is a derivative of Rhino, meaning "nose.") Symptoms include nasal congestion, a clear runny nose, sneezing, nose and eye itching, and tearing eyes. 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. Eye itching, redness, and tearing frequently accompany the nasal symptoms.

Allergy: A misguided reaction to foreign substances by the immune system, the body system of defense against foreign invaders, particularly pathogens (the agents of infection). The allergic reaction is misguided in that these foreign substances are usually harmless. The substances that trigger allergy are called allergen. Examples include pollens, dust mite, molds, danders, and certain foods. People prone to allergies are said to be allergic or atopic.
See the entire definition of Allergy

Allergy shots: See Allergy desensitization.

Anaphylactic shock: A widespread and very serious allergic reaction. Symptoms include dizziness, loss of consciousness, labored breathing, swelling of the tongue and breathing tubes, blueness of the skin, low blood pressure, heart failure, and death. Immediate emergency treatment is required for this type of shock, including administration of antivenom in the case of bee or wasp stings.

Anaphylaxis: Allergic reaction. In severe cases, this can include potentially deadly anaphylactic shock.

Antibody: An immunoglobulin, a specialized immune protein, produced because of the introduction of an antigen into the body, and which possesses the remarkable ability to combine with the very antigen that triggered its production.
See the entire definition of Antibody

Aspirin: A good example of a tradename that entered into the language, Aspirin was once the Bayer trademark for acetylsalicylic acid.
See the entire definition of Aspirin

Asthma: A common disorder in which chronic inflammation of the bronchial tubes (bronchi) makes them swell, narrowing the airways. Asthma involves only the bronchial tubes and does not affect the air sacs (alveoli) or the lung tissue (the parenchyma of the lung) itself.
See the entire definition of Asthma

Atopic: Prone to allergies or characterized by allergy.

Atopic dermatitis: A skin disease characterized by areas of severe itching, redness, scaling, and loss of the surface of the skin (excoriation). When the eruption (rash) has been present for a prolonged time, chronic changes occur due to the constant scratching and rubbing known as lichenification (thickening of the skin with accentuation of the skin lines to form a crisscross pattern).
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Bacteria: Single-celled microorganisms which can exist either as independent (free-living) organisms or as parasites (dependent upon another organism for life).
See the entire definition of Bacteria

Bee sting: Stings from bees and other large stinging insects such as yellow jackets, hornets and wasps can trigger allergic reactions varying greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective. (The three "A's" of insect allergy are Adrenaline, Avoidance and Allergist.)

Blood pressure: The blood pressure is the pressure of the blood within the arteries. It is produced primarily by the contraction of the heart muscle. It's measurement is recorded by two numbers. The first (systolic pressure) is measured after the heart contracts and is highest. The second (diastolic pressure) is measured before the heart contracts and lowest. A blood pressure cuff is used to measure the pressure. Elevation of blood pressure is called "hypertension".

Breathing: The process of respiration, during which air is inhaled into the lungs through the mouth or nose due to muscle contraction, and then exhaled due to muscle relaxation.

Chest: The area of the body located between the neck and the abdomen. The chest contains the lungs, the heart and part of the aorta. The walls of the chest are supported by the dorsal vertebrae, the ribs, and the sternum.
See the entire definition of Chest

Circulation: The movement of fluid in a regular or circuitous course. Although the noun "circulation" does not necessarily refer to the circulation of the blood, for all practical purposes today it does. Heart failure is an example of a problem with the circulation.

Cluster: In epidemiology, an aggregation of cases of a disease or another health-related condition, such as a cancer or birth defect, closely grouped in time and place. The number of cases in the cluster may or may not exceed the expected number. This is determined by cluster analysis, a set of statistical methods used to analyze clusters.

Congestion: An abnormal or excessive accumulation of a body fluid. The term is used broadly in medicine. Examples include nasal congestion (excess mucus and secretions in the air passages of the nose) seen with a common cold and congestion of blood in the lower extremities seen with some types of heart failure.

Conjunctivitis: Inflammation of the conjunctiva, the membrane on the inner part of the eyelids and the membrane covering the white of the eye. The conjunctival membranes react to a wide range of bacteria, viruses, allergy-provoking agents, irritants and toxic agents. Viral and bacterial forms of conjunctivitis are common in childhood. Conjunctivitis is also called pinkeye and red eye.
See the entire definition of Conjunctivitis

Contact dermatitis: A skin condition caused by contact between skin and some substance. Includes irritant contact dermatitis (a rash brought on purely by repeated irritation from a substance such as water causing "dish pan hands") and allergic contact dermatitis (involving a specific sensitivity or allergy to a specific substance such as poison ivy).

Dander: Tiny scales shed from human or animal skin or hair. Dander floats in the air, settles on surfaces and makes up much household dust. Cat dander is a classic cause of allergic reactions.

Danders: See: Dander.

Dermatitis: Inflammation of the skin, either due to direct contact with an irritating substance, or to an allergic reaction. Symptoms of dermatitis include redness, itching, and in some cases blistering.
See the entire definition of Dermatitis

Diarrhea: A familiar phenomenon with unusually frequent or unusually liquid bowel movements, excessive watery evacuations of fecal material. The opposite of constipation. The word "diarrhea" with its odd spelling is a near steal from the Greek "diarrhoia" meaning "a flowing through." Plato and Aristotle may have had diarrhoia while today we have diarrhea. There are myriad infectious and noninfectious causes of diarrhea.
See the entire definition of Diarrhea

Drip: In medical usage, a drip is not a dull, unattractive person but a device for administering a fluid drop-by-drop into a vein. It is an intravenous (IV) fluid dripping into a vein, an intravenous fluid drip, a solution (usually a balanced electrolyte solution) administered directly into the venous circulation. It is, for short, an IV.

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Dust mite: A tiny microscopic organism that is the primary cause of allergies related to house dust. The term "dust mite allergy" is a misnomer because it is the excretion of these mites to which people are allergic. Dust mites can therefore trigger allergic reactions even when dead.

Eczema: A particular type of inflammatory reaction of the skin in which there are typically vesicles (tiny blister-like raised areas) in the first stage followed by erythema (reddening), edema (swelling), papules (bumps), and crusting of the skin followed, finally, by lichenification (thickening) and scaling of the skin. Eczema characteristically causes itching and burning of the skin.
See the entire definition of Eczema

Elbow: The juncture of the long bones in the middle portion of the arm. The bone of the upper arm (humerus) meets both the ulna (the inner bone of the forearm) and radius (the outer bone of the forearm) to form a hinge joint at the elbow. The radius and ulna also meet one another in the elbow to permit a small amount of rotation of the forearm. The elbow therefore functions to move the arm like a hinge (forward and backward) and in rotation (outward and inward). The biceps muscle is the major muscle that flexes the elbow hinge, and the triceps muscle is the major muscle that extends it. The primary stability of the elbow is provided by the ulnar collateral ligament, located on the medial (inner) side of the elbow. The outer bony prominence of the elbow is the lateral epicondyle, a part of the humerus bone. Tendons attached to this area can be injured, causing inflammation or tendonitis (lateral epicondylitis, or tennis elbow). The inner portion of the elbow is a bony prominence called the medial epicondyle of the humerus. Additional tendons from muscles attach here and can be injured, likewise causing inflammation or tendonitis (medial epicondylitis, or golfer's elbow). See also: Elbow bursitis; Elbow pain; Nursemaid's elbow.

Eyelid: The lid or cover of the eye, a movable fold of skin and muscle that can be closed over the eyeball or opened at will. Each eye has an upper and a lower lid. An eyelid is also called a palpebra.

Fever: Although a fever technically is any body temperature above the normal of 98.6 degrees F. (37 degrees C.), in practice a person is usually not considered to have a significant fever until the temperature is above 100.4 degrees F (38 degrees C.).
See the entire definition of Fever

Gastrointestinal: Adjective referring collectively to the stomach and small and large intestines.
See the entire definition of Gastrointestinal

Gastrointestinal tract: The tube that extends from the mouth to the anus in which the movement of muscles and release of hormones and enzymes digest food. The gastrointestinal tract starts with the mouth and proceeds to the esophagus, stomach, duodenum, small intestine, large intestine (colon), rectum and, finally, the anus. Also called the alimentary canal, digestive tract and, perhaps most often in conversation, the GI tract.

Genetic: Having to do with genes and genetic information.

Hay fever: A seasonal allergy to airborne particles characterized by itchy eyes, runny nose, nasal congestion, sneezing, itchy throat, and excess mucus.
See the entire definition of Hay fever

Heredity: Genetic transmission from parent to child.

Histamine: Substance that plays a major role in many allergic reactions. Histamine dilates blood vessels and makes the vessel walls abnormally permeable.

Hives: A raised, itchy area of skin that is usually a sign of an allergic reaction. It can be rounded or flat-topped but is always elevated above the surrounding skin. It reflects circumscribed dermal edema (local swelling of the skin). The hives are usually well circumscribed but may be coalescent and will blanch with pressure. They typically last less than 4 hours but they may stay for days or weeks. Approximately 20% of the population has experienced a bout of hives.
See the entire definition of Hives

Immune: Protected against infection. The Latin immunis means free, exempt.

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.
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Immunity: The condition of being immune. Immunity can be innate (for example, humans are innately immune to canine distemper) or conferred by a previous infection or immunization.

Immunoglobulin: A protein produced by plasma cells and lymphocytes and characteristic of these types of cells. Immunoglobulins play an essential role in the body's immune system. They attach to foreign substances, such as bacteria, and assist in destroying them. Immunoglobulin is abbreviated Ig. The classes of immunoglobulins are termed immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), immunoglobulin D (IgD) and immunoglobulin E (IgE).

Immunoglobulin E: Abbreviated IgE. A class of immunoglobulins that includes the antibodies elicited by an allergic substance (allergen). A person who has an allergy usually has elevated blood levels of IgE. IgE antibodies attack and engage the invading army of allergens.

Infection: The growth of a parasitic organism within the body. (A parasitic organism is one that lives on or in another organism and draws its nourishment therefrom.) A person with an infection has another organism (a "germ") growing within him, drawing its nourishment from the person.
See the entire definition of Infection

Inflammation: A basic way in which the body reacts to infection, irritation or other injury, the key feature being redness, warmth, swelling and pain. Inflammation is now recognized as a type of nonspecific immune response.
See the entire definition of Inflammation

Insect sting: Stings from large stinging insects such as bees, hornets, yellow jackets and wasps can trigger allergic reactions varying greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective.

Insulin: A natural hormone made by the pancreas that controls the level of the sugar glucose in the blood. Insulin permits cells to use glucose for energy. Cells cannot utilize glucose without insulin.
See the entire definition of Insulin

Itching: An uncomfortable sensation in the skin that feels as if something is crawling on the skin or in the skin, and makes the person want to scratch the affected area.
See the entire definition of Itching

Low blood pressure: Any blood pressure that is below the normal expected for an individual in a given environment. Low blood pressure is also referred to as hypotension.
See the entire definition of Low blood pressure

Lungs: The lungs are a pair of breathing organs located with the chest which remove carbon dioxide from and bring oxygen to the blood. There is a right and left lung.

Mite: A tiny eight-legged creature belonging to the Order Acarina related to spiders and ticks. Some mites live freely and others as parasites. Mites can attack plants and animals, carry disease, and cause allergies. acaricide.

Mold: A very large group of microscopic fungi that live on plant or animal matter. Most are filamentous organisms and produce spores that can be air-, water-, or insect-borne. A common trigger for allergies.
See the entire definition of Mold

Mouth: 1. The upper opening of the digestive tract, beginning with the lips and containing the teeth, gums, and tongue. Foodstuffs are broken down mechanically in the mouth by chewing and saliva is added as a lubricant. Saliva contains amylase, an enzyme that digests starch. 2. Any opening or aperture in the body. The mouth in both senses of the word is also called the os, the Latin word for an opening, or mouth. The o in os is pronounced as in hope. The genitive form of os is oris from which comes the word oral.

Mucus: A thick slippery fluid produced by the membranes lining certain organs such as the nose, mouth, throat, and vagina. Mucus is the Latin word for "a semifluid, slimy discharge from the nose." Note that mucus is a noun while the adjective is mucous.

Nasal: Having to do with the nose. Nasal drops are intended for the nose, not (for example) the eyes. The word "nasal" came from the Latin "nasus" meaning the nose or snout.

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Nausea: Nausea, is the urge to vomit. It can be brought by many causes including, systemic illnesses, such as influenza, medications, pain, and inner ear disease. When nausea and/or vomiting are persistent, or when they are accompanied by other severe symptoms such as abdominal pain, jaundice, fever, or bleeding, a physician should be consulted.

Nickel: A silver-white metallic element. Long-term exposure to nickel, such as from jewelry, can cause a form of contact dermatitis called nickel dermatitis. Exposure to nickel fumes can cause nasal cancer and lung cancer.

Nose: The external midline projection from the face.
See the entire definition of Nose

Oxygen: A colorless, odorless and tasteless gas that makes up about 20% of the air we breathe (and at least half the weight of the entire solid crust of the earth) and which combines with most of the other elements to form oxides. Oxygen is essential to human, animal and plant life.
See the entire definition of Oxygen

Pain: An unpleasant sensation that can range from mild, localized discomfort to agony. Pain has both physical and emotional components. The physical part of pain results from nerve stimulation. Pain may be contained to a discrete area, as in an injury, or it can be more diffuse, as in disorders like fibromyalgia. Pain is mediated by specific nerve fibers that carry the pain impulses to the brain where their conscious appreciation may be modified by many factors.
See the entire definition of Pain

Poison: Any substance that can cause severe distress or death if ingested, breathed in, or absorbed through the skin. Many substances that normally cause no problems, including water and most vitamins, can be poisonous if taken in too large of a quantity. Poison treatment depends on the substance: if there are treatment instructions on the substance's container and you are sure it contained no other item, follow those directions immediately. Always contact your nearest Poison Control Center if you are concerned about possible poison ingestion.

Poison ivy: Skin inflammation resulting from contact with oils from the poison ivy vine. Chemicals produced by this vine cause an immune reaction, producing redness, itching, and blistering of the skin.
See the entire definition of Poison ivy

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.

Protein: A large molecule composed of one or more chains of amino acids in a specific order determined by the base sequence of nucleotides in the DNA coding for the protein.
See the entire definition of Protein

Proteins: Large molecules composed of one or more chains of amino acids in a specific order determined by the base sequence of nucleotides in the DNA coding for the protein.
See the entire definition of Proteins

Rash: Breaking out (eruption) of the skin. Medically, a rash is referred to as an exanthem.

Rhinitis: Irritation of the nose. Derived from the Greek word rhinos meaning of the nose.

Runny nose: Rhinorrhea is the medical term for this common problem. From the Greek words "rhinos" meaning "of the nose" and "rhoia" meaning "a flowing."

Serum: The clear liquid that can be separated from clotted blood. Serum differs from plasma, the liquid portion of normal unclotted blood containing the red and white cells and platelets. It is the clot that makes the difference between serum and plasma.
See the entire definition of Serum

Shock: In medicine, shock is a critical condition brought on by a sudden drop in blood flow through the body. There is failure of the circulatory system to maintain adequate blood flow. This sharply curtails the delivery of oxygen and nutrients to vital organs. It also compromises the kidney 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 (hypovolemic shock) and not enough output of blood by the heart (cardiogenic shock). The signs and symptoms of shock include low blood pressure (hypotension), overbreathing (hyperventilation), a weak rapid pulse, cold clammy grayish-bluish (cyanotic) skin, decreased urine flow (oliguria), and mental changes (a sense of great anxiety and foreboding, confusion and, sometimes, combativeness).
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Shortness of breath: Difficulty in breathing. Medically referred to as dyspnea. Shortness of breath can be caused by respiratory (breathing passages and lungs) or circulatory (heart and blood vessels) conditions. See also dyspnea.

Spasm: A brief, automatic jerking movement. A muscle spasm can be quite painful, with the muscle clenching tightly. A spasm of the coronary artery can cause angina. Spasms in various types of tissue may be caused by stress, medication, over-exercise, or other factors.

Stomach: 1. The sac-shaped digestive organ that is located in the upper abdomen, under the ribs. The upper part of the stomach connects to the esophagus, and the lower part leads into the small intestine.
See the entire definition of Stomach

Stomach cramps: A nonmedical term most often used to describe pain in the mid- or upper abdominal area. Abdominal pain (pain in the belly) can come from conditions affecting a variety of organs and does not necessarily arise from the stomach even though an individual may perceive that pain is originating in the stomach. Various organs can be the source of pain in the upper abdomen, including the small intestine, colon, liver, gallbladder, and pancreas.

Stuffy nose: The presence of increased secretions and mucus in the nasal passages, most commonly arising as a result of a common cold, allergic reaction, or inflammation or infection of the paranasal sinuses (sinus infection).

Substance: 1. Material with particular features, as a pressor substance.
2. The material that makes up an organ or structure. Also known in medicine as the substantia.
3. A psychoactive drug as, for example, in substance abuse.

Throat: The throat is the anterior (front) portion of the neck beginning at the back of the mouth, consisting anatomically of the pharynx and larynx. The throat contains the trachea and a portion of the esophagus.

Tongue: The tongue is a strong muscle anchored to the floor of the mouth. It is covered by the lingual membrane which has special areas to detect tastes.
See the entire definition of Tongue

Trigger: Something that either sets off a disease in people who are genetically predisposed to developing the disease, or that causes a certain symptom to occur in a person who has a disease. For example, sunlight can trigger rashes in people with lupus.

Tubes: The "tubes" are medically known as the Fallopian tubes. There are two Fallopian tubes, one on each side, which transport the egg from the ovary to the uterus (the womb). The Fallopian tubes have small hair-like projections called cilia on the cells of the lining.
See the entire definition of Tubes

Urine: Liquid waste. The urine is a clear, transparent fluid. It normally has an amber color. The average amount of urine excreted in 24 hours is from 40 to 60 ounces (about 1,200 cubic centimeters). Chemically, the urine is mainly an aqueous (watery) solution of salt (sodium chloride) and substances called urea and uric acid. Normally, it contains about 960 parts of water to 40 parts of solid matter. Abnormally, it may contain sugar (in diabetes), albumen (a protein) (as in some forms of kidney disease), bile pigments (as in jaundice), or abnormal quantities of one or another of its normal components.

Urticaria: Another name for the hives. Raised, itchy areas of skin that are usually a sign of an allergic reaction. Hives can be rounded or flat-topped but are always elevated above the surrounding skin. They reflect circumscribed dermal edema (local swelling of the skin). The hives are usually well circumscribed but may be coalescent and will blanch with pressure.
See the entire definition of Urticaria

Vaccines: Microbial preparations of killed or modified microorganisms that can stimulate an immune response in the body to prevent future infection with similar microorganisms. These preparations are usually delivered by injection.

Venom: A poison, particularly one secreted by an animal. For examples, bee venom, snake venom, scorpion venom, and spider venom. Snake venom is also called venin.

Virus: A microorganism smaller than a bacteria, which cannot grow or reproduce apart from a living cell. A virus invades living cells and uses their chemical machinery to keep itself alive and to replicate itself. It may reproduce with fidelity or with errors (mutations)-this ability to mutate is responsible for the ability of some viruses to change slightly in each infected person, making treatment more difficult.
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Wheezing: A whistling noise in the chest during breathing when the airways are narrowed or compressed.

Womb: The womb (uterus) is a hollow, pear-shaped organ located in a woman's lower abdomen between the bladder and the rectum. The narrow, lower portion of the uterus is the cervix; the broader, upper part is the corpus. The corpus is made up of two layers of tissue.


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    • Bee and Wasp Sting
      • Bees, wasps, and fire ants are related insects that belong to the Hymenoptera order. There are thousands of species of wasps found throughout the world. Common wasps are yellow jackets and hornets. Types of bees include honey bees, the Africanized honey bee (killer bee), and the bumble bee. There are four types of reactions to a bee or wasp sting; 1) local reaction, 2) systemic allergic reaction, 3) toxic reaction, and 4) delayed reaction. Individuals who have a systemic or toxic reaction generally require immediate medical treatment to prevent anaphylactic reaction, and possibly death.
    • Latex Allergy
    • Adult-Onset Asthma
      • Adult-onset asthma is asthma that is diagnosed in people over 20 years of age. Symptoms include wheezing, coughing, shortness of breath and difficulty breathing. Treatment may involve anti-inflammatory medications or bronchodilators.
    • Bug Bites and Stings
      • Bug bites and stings have been known to transmit insect-borne illnesses such as West Nile virus, Rocky Mountain spotted fever, and Lyme disease. Though most reactions to insect bites and stings are mild, some reactions may be life-threatening. Preventing bug bites and stings with insect repellant, wearing the proper protective attire, and not wearing heavily scented perfumes when in grassy, wooded, and brushy areas is key.
    • Insect Sting Allergies
      • The majority of stinging insects in the United States are from Bees, Yellow Jackets, Hornets, Wasps and Fire Ants. Severity of reactions to stings varies greatly. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective.
    • Indoor Allergens
      • Common sources of indoor allergens include dust mites, cockroaches, molds, pets, and plants. Managing allergies caused by indoor allergens means reducing your exposure to them.
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Allergies & Asthma

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Symptom Checker: Your Guide to Symptoms & Signs: Pinpoint Your Pain



Allergy

Poison ivy, oak, and sumac facts

  • Many people are susceptible to the rashes of poison ivy, oak, and sumac.


  • The sap oil, called urushiol, causes the skin rash.


  • Poison ivy is not contagious.


  • Washing the oily sap from the skin with water and soap immediately can help prevent the rash.


  • Avoiding direct contact with the plants can prevent the rash.

What causes the rash? How do I identify poison ivy, oak, and sumac?

Poison ivy is a common cause of contact dermatitis, an allergic reaction to something that comes in direct contact with the skin. Allergic contact dermatitis as a response to plants is sometimes referred to as allergic phytodermatitis. This condition can be quite unpleasant but does not typically pose serious health risks. Prevention of the condition is best.

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