Allergic Reaction Glossary of Medical Terms

Allergen: A substance that is foreign to the body and can cause an allergic reaction in certain people. For examples, pollen, dander, mold.
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Allergic reaction: The hypersensitive response of the immune system of an allergic individual to a substance.
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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.
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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 .
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Allergy shots: See Allergy desensitization .
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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 .
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Anaphylaxis: Allergic reaction. In severe cases, this can include potentially deadly anaphylactic shock .
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Angioedema: Like hives but affects deeper skin layer.
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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.
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Antigen: A substance that is capable of causing the production of an antibody .
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Antihistamines: Drugs that combat the histamine released during an allergic reaction by blocking the action of the histamine on the tissue. Antihistamines do not stop the formation of histamine nor do they stop the conflict between the IgE and antigen. Therefore, antihistamines do not stop the allergic reaction but protect tissues from some of its effects. Antihistamines frequently cause mouth dryness and sleepiness. Newer "non sedating" antihistamines are generally thought to be somewhat less effective. Antihistamine side effects that very occasionally occur include urine retention in males and fast heart rate.
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Aspirin: A good example of a tradename that entered into the language, Aspirin was once the Bayer trademark for acetylsalicylic acid .
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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.
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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).
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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 ".
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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.
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Bumps: The raised area of a bump or bruise results from blood leaking from these injured blood vessels into the tissues as well as from the body's response to the injury. A purplish, flat bruise that occurs when blood leaks out into the top layers of skin is referred to as an ecchymosis.
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Cardiac: Having to do with the heart.
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Cell: The basic structural and functional unit in people and all living things. Each cell is a small container of chemicals and water wrapped in a membrane .
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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 .
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Chronic: This important term in medicine comes from the Greek chronos, time and means lasting a long time.
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Chronic obstructive pulmonary disease : COPD. Any disorder that persistently obstructs bronchial airflow. COPD mainly involves two related diseases -- chronic bronchitis and emphysema. Both cause chronic obstruction of air flowing through the airways and in and out of the lungs. The obstruction is generally permanent and progresses (becomes worse) over time.
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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 .
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COPD: Chronic obstructive pulmonary disease . Any disorder that persistently obstructs bronchial airflow. COPD mainly involves two related diseases -- chronic bronchitis and emphysema. Both cause chronic obstruction of air flowing through the airways and in and out of the lungs. The obstruction is generally permanent and progresses (becomes worse) over time.
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Corticosteroid: Any of the steroid hormones made by the cortex (outer layer) of the adrenal gland. Cortisol is a corticosteroid.
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Cough: A rapid expulsion of air from the lungs typically in order to clear the lung airways of fluids, mucus, or material. Also called tussis.
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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.
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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.
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Dilation: The process of enlargement, stretching, or expansion. The word "dilatation" means the same thing. Both come from the Latin "dilatare" meaning "to enlarge or expand."
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Discharge: 1.The flow of fluid from part of the body, such as from the nose or vagina.
2. The passing of an action potential, such as through a nerve or muscle fiber .
3. The release of a patient from a course of care. The doctor may then dictate a discharge summary.
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Emergency department: The department of a hospital responsible for the provision of medical and surgical care to patients arriving at the hospital in need of immediate care. Emergency department personnel may also respond to certain situations within the hospital such cardiac arrests.
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Epinephrine: A substance produced by the medulla (inside) of the adrenal gland. The name epinephrine was coined in 1898 by the American pharmacologist and physiologic chemist (biochemist) John Jacob Abel who isolated it from the adrenal gland which is located above (epi-) the kidney ("nephros" in Greek). (Abel also crystallized insulin ). Technically speaking, epinephrine is a sympathomimetic catecholamine. It causes quickening of the heart beat, strengthens the force of the heart's contraction, opens up the airways (bronchioles) in the lungs and has numerous other effects. The secretion of epinephrine by the adrenal is part of the fight-or-flight reaction. Adrenaline is a synonym of epinephrine and is the official name in the British Pharmacopoeia.
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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.).
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Hay fever: A seasonal allergy to airborne particles characterized by itchy eyes, runny nose, nasal congestion, sneezing, itchy throat, and excess mucus.
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Headache : A pain in the head with the pain being above the eyes or the ears, behind the head (occipital), or in the back of the upper neck. Headache, like chest pain or back ache, has many causes.
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High blood pressure : Also known as hypertension, high blood pressure is, by definition, a repeatedly elevated blood pressure exceeding 140 over 90 mmHg -- a systolic pressure above 140 with a diastolic pressure above 90.
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Histamine: Substance that plays a major role in many allergic reactions. Histamine dilates blood vessels and makes the vessel walls abnormally permeable.
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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.
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Immune: Protected against infection. The Latin immunis means free, exempt.
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Immune response: Any reaction by the immune system.
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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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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).
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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.
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Immunology: The study of all aspects of the immune system including its structure and function, disorders of the immune system, blood banking, immunization and organ transplantation.
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Immunotherapy: Treatment to stimulate or restore the ability of the immune (defense) system to fight infection and disease. Biological therapy is thus any form of treatment that uses the body's natural abilities that constitute the immune system to fight infection and disease or to protect the body from some of the side effects of treatment.
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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 .
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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.
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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.
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Lips: Aside from the lips of the mouth, there are two pairs of lips at the entrance to the vagina . They are the labia majora (the larger outside pair) and the labia minora (the smaller inside pair). Together they form part of the vulva (the female external genitalia ).
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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.
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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.
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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 .
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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.
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Muscle: Muscle is the tissue of the body which primarily functions as a source of power. There are three types of muscle in the body. Muscle which is responsible for moving extremities and external areas of the body is called "skeletal muscle." Heart muscle is called "cardiac muscle." Muscle that is in the walls of arteries and bowel is called "smooth muscle."
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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.
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NIEHS: Stands for National Institute of Environmental Health Sciences, one of the National Institutes of Health in the U.S., whose mission is to "reduce the burden of human illness and dysfunction from environmental causes by defining how environmental exposures, genetic susceptibility, and age interact to affect an individual's health."
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Nose: The external midline projection from the face.
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Ointment: A medication preparation that is applied topically (onto the skin). An ointment has an oil base whereas a cream is water-soluble. (The word ointment comes from the Latin ungere meaning anoint with oil).
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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.
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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.
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Penicillin : The most famous of all antibiotics, named for the fungal mold Penicillium notatum from which it is derived. Penicillin acts by destroying the cell wall of bacteria .
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Pharmacy: A location where prescription drugs are sold. A pharmacy is, by law, constantly supervised by a licensed pharmacist.
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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.
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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.
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Poison oak: Poison oak is a form of "contact dermatitis" or inflammation of the skin resulting from chemicals produced from the poison oak plant contacting the skin. The chemicals cause an immune reaction producing redness, itching and blistering of the skin.
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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.
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Prescription: A physician's order for the preparation and administration of a drug or device for a patient. A prescription has several parts. They include the superscription or heading with the symbol "R" or "Rx", which stands for the word recipe (meaning, in Latin, to take); the inscription, which contains the names and quantities of the ingredients; the subscription or directions for compounding the drug; and the signature which is often preceded by the sign "s" standing for signa (Latin for mark), giving the directions to be marked on the container.
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Pulmonary: Having to do with the lungs. (The word comes from the Latin pulmo for lung).
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Pulse: The rhythmic contraction and expansion of an artery due to the surge of blood from the beat of the heart. The pulse is most often measured by feeling the arteries of the wrist. There is also a pulse, although far weaker, in veins.
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Rash : Breaking out (eruption) of the skin. Medically, a rash is referred to as an exanthem.
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RAST: An allergy test done on a sample of blood. The aim with RAST, as with skin tests, is to check for allergic sensitivity to specific substances.
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Referral: The recommendation of a medical or paramedical professional. If you get a referral to ophthalmology, for example, you are being sent to the eye doctor. In HMOs and other managed care schemes, a referral is usually necessary to see any practitioner or specialist other than your primary care physician (PCP), if you want the service to be covered. The referral is obtained from your PCP, who may require a telephone or office consultation first.
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Respiratory: Having to do with respiration, the exchange of oxygen and carbon dioxide. From the Latin re- (again) + spirare (to breathe) = to breathe again.
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Rhinitis: Irritation of the nose. Derived from the Greek word rhinos meaning of the nose.
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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."
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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.
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Sinus: 1. An air-filled cavity in a dense portion of a skull bone. The sinuses decrease the weight of the skull. The sinuses are formed in four right-left pairs. The frontal sinuses are positioned behind the forehead, while the maxillary sinuses are behind the cheeks. The sphenoid and ethmoid sinuses are deeper in the skull behind the eyes and maxillary sinuses. The sinuses are lined by mucous-secreting cells. Air enters the sinuses through small opening in bone called ostia. If an ostium is blocked, air cannot pass into the sinus and likewise mucous cannot drain out. See also: Sinusitis .
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Sodium: The major positive ion (cation) in fluid outside of cells. The chemical notation for sodium is Na⁺. When combined with chloride, the resulting substance is table salt.
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Steroid: A general class of chemical substances that are structurally related to one another and share the same chemical skeleton (a tetracyclic cyclopenta[a]phenanthrene skeleton).
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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.
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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 ).
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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 .
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Sweating: The act of secreting fluid from the skin by the sweat (sudoriferous) glands. These are small tubular glands situated within and under the skin (in the subcutaneous tissue). They discharge by tiny openings in the surface of the skin.
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Therapy: The treatment of disease .
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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 .
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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.
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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 .
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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.
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Unconscious: 1. Interruption of awareness of oneself and one's surroundings, lack of the ability to notice or respond to stimuli in the environment. A person may become unconscious due to oxygen deprivation, shock, central nervous system depressants such as alcohol and drugs, or injury.
2. In psychology, that part of thought and emotion that happens outside everyday awareness.
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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.
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Viruses: Small living particles that can infect cells and change how the cells function. Infection with a virus can cause a person to develop symptoms. The disease and symptoms that are caused depend on the type of virus and the type of cells that are infected.
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Wheezing: A whistling noise in the chest during breathing when the airways are narrowed or compressed.
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White blood cell: One of the cells the body makes to help fight infections. There are several types of white blood cells ( leukocytes ). The two most common types are the lymphocytes and neutrophils (also called polymorphonuclear leukocytes, PMNs, or "polys").
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