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Allergen: A substance that triggers an allergic reaction.

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Allergic Rhinitis: An allergy affecting the mucus membrane of the nose. Seasonal allergic rhinitis is often called "hay fever."

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Allergist: A doctor that diagnoses, treats, and manages allergy-related conditions.

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Ana-Kit: A device used to inject epinephrine during an anaphylaxis attack.

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Anaphylaxis: A life-threatening allergic reaction that involves the entire body. Anaphylaxis may result in shock or death, and thus requires immediate medical attention

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Animal dander: The small scales or pieces of skin, often containing proteins secreted by oil glands, which are shed by an animal. These proteins are the major causes of allergies to pets.

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Antibiotics: A class of medications used to treat bacterial infections. Certain antibiotics, such as penicillin, may cause an allergic reaction in some people.

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Antibody: A protein in the immune system that recognizes and attacks foreign substances in the body.

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Anticonvulsant: A medication used to prevent or treat seizures. Certain anticonvulsants may cause an allergic reaction in some people.

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Antihistamines: A class of medications used to block the action of histamines in the body and prevent the symptoms of an allergic reaction.

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Asthma: An inflammatory disorder of the airways, causing periodic attacks of wheezing, coughing, chest tightness, and shortness of breath.

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Atopic dermatitis: A chronic skin rash, also known as "eczema," that often appears in the first few years of life.

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Basophil: An immune system cell that attaches to antibodies and circulates through out the blood.

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Beta-blockers: A class of blood pressure medications that ease the heart's pumping action and widen the blood vessels. Beta-blockers counteract the effects of epinephrine used for emergency treatment of anaphylactic shock and should not be used during immunotherapy.

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Bronchial tubes: The lower sections of the airway that lead into the lungs.

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Challenge test: A test used to confirm an allergy to specific substance. A doctor will administer small but increasing amounts of a suspected allergen until an allergic response is noticed. Due to the risk of anaphylaxis, this should only be performed under a controlled setting.

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Conjunctivitis: Inflammation of the conjunctiva, or the mucous membrane surrounding the eye. Also known as pinkeye.

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Contact dermatitis: An allergic reaction resulting from skin contact to an allergen.

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Corticosteroid: An anti-inflammatory medication used to treat the itching and swelling associated with some allergic reactions.

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Cromolym sodium: An anti-inflammatory nasal spray used to treat and sometimes prevent allergic rhinitis.

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Decongestants: A class of medications used for nasal congestion. Decongestants are available in oral doses, nasal sprays, or eye drops (for conjunctivitis).

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Dust mites: A microscopic organism that lives in dust.

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Eczema: See Atopic dermatitis.

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Eosinophil: A specific type of immune cell that can cause tissue damage in the late phase of an allergic reaction.

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Epinepherine: A medication used for immediate treatment of anaphylaxis by raising blood pressure and heart rate back to normal levels. Epinepherine is also known as adrenaline.

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EpiPen: A device used to inject epinephrine during an anaphylaxis attack.

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Heparin: A chemical released by basophils and mast cells that causes nearby tissues to become swollen and inflamed.

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Histamine: A chemical released by basophils and mast cells that causes nearby tissues to become swollen and inflamed.

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Hives: See urticaria.

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Hypertension: High blood pressure. When blood pushes against artery walls harder than normal.

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Immunoglobulin E: A type of antibody responsible for most allergic reactions.

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Immunotherapy: A series of shots that help build up the immune system's tolerance to an allergen.

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Insulin: A hormone that regulates blood sugar levels. Diabetics who take insulin derived from animals may have allergic reactions.

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Intradermal test: A test where an allergen is injected just underneath the skin. Intradermal tests are generally used when results from a skin prick test are unclear.

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Late Phase: The period 4 - 24 hours after exposure to an allergen where tissue damage may occur.

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Leukotrienes: Inflammatory substances that are released by mast cells during an allergic response or asthma attack.

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Lymphocyte: A specific type of immune cell that can cause tissue damage in the late phase of an allergic reaction.

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Mast cell: An immune system cell which attaches to antibodies and is located in the tissue that lines the nose, bronchial tubes, gastrointestinal tract, and the skin

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Neocromil sodium: An inhaled medication used to treat inflammation involved with asthma.

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Neutrophil: A specific type of immune cell that can cause tissue damage in the late phase of an allergic reaction.

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Otitis media: A middle ear infection. Otitis media with effusion occurs when fluid builds up within the ear.

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Radioallergosorbant Test (RAST): A blood test that measures the amount of IgE antibody produced when the sample is mixed with a specific allergen.

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Rhinitis: An inflammation of the nasal passageways, particularly with discharge.

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Sinusitis: An inflammation or infection of one or more sinuses. The sinuses are hollow air spaces located around the nose and eyes.

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Skin prick test: A test where a needle is used to scratch the skin with a small amount of allergen. A response can usually be seen within 15 - 20 minutes.

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Urticaria: Raised areas of the skin that are often red, warm, and itchy. Urticaria is also known as hives.

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Urushiol: An oil found on poison ivy, oak, and sumac.

Contact with poison ivy is one of the most frequent causes of skin rash in children during the spring, summer, and fall seasons. The resins of these plants, called urushiol, cause an allergic reaction in more than 50% of the population. Exposure to the smoke of these burning plants can cause the same reaction.

Poison ivy can be found in every region of the United States except the Southwest, Alaska, and Hawaii. It appears as a weed with three shiny green leaves and a red stem. The plant grows in the form of a vine, often along riverbanks.

Poison oak is primarily found on the West Coast. It grows in the form of a shrub and has three leaves similar to poison ivy.

Poison sumac grows abundantly along the Mississippi River, but is far less common in other regions. It grows as a shrub. Each stem contains 7 - 13 leaves arranged in pairs.

Causes

Dermatitis is caused by a sensitivity to the resin of these plants. The rash is spread by the oils touching various parts of the body. It is not spread by the fluid of the blisters it creates, thus it is not contagious unless the resin remains on the skin and is touched by another person.

However, the oily resin usually enters the skin rapidly, and is seldom transferred person to person. Conversely, the resin may persist for long periods on contaminated clothing, pets, tools, etc., and sensitive individuals can easily develop the rash from delayed contact with contaminated items.

This is a true allergy. Most people will have no reaction the first time they are exposed. In fact, children under the age of 7 are rarely sensitive. Sensitivity is particularly rare under the age of one, and when infants do break out, the rash is usually mild.

Symptoms

  • Redness and extreme itching are the first signs.
  • Rash erupts on areas exposed to the resin, and it is often in the pattern of streaks or patches consistent with where the plant touched the skin.
  • Rash is in the form of red bumps (papules) and may also form large, weeping blisters.
  • Worst stage of the rash is experienced 4 - 7 days after exposure.
  • Rash may last for 1 - 3 weeks.

Symptoms usually appear within 2 days of exposure, but rarely may appear as late as 2 weeks later. Reactions can vary from mild in some individuals to very severe in highly sensitive individuals. Hospitalization is sometimes required.

First aid

  • The skin should be washed thoroughly with water only as soon as possible following exposure. Next, liberally apply rubbing (isopropyl) alcohol, if available, to the affected area. Rubbing alcohol helps remove the plant oils and prevents spreading. Soap is less effective, but may help if rubbing alcohol is not available. Because the resin enters skin quickly, it should be washed off completely within 30 minutes to prevent a reaction.
  • Camping stores sell products that bind the resins, and which may be more effective at removing the resins from your body.
  • Scrub under the fingernails with a brush to prevent spreading of the resin to other parts of the body by touching or scratching.
  • Wash the clothing and shoes of the exposed person with soap and hot water. Resin can linger on these surfaces for days.
  • Bathe animals that may have been exposed and can carry the resin on their fur.
  • Body heat and sweating can aggravate itching. Keep the victim cool and apply cool compresses to the skin.
  • Calamine lotion and topical hydrocortisone cream may be applied to the skin to help decrease itching and blistering.
  • Antihistamines, such as Benadryl (diphenhydramine) help relieve itching and can be mildly sedating. Bathing in tepid water with one cup of Aveeno oatmeal per tub may also soothe itchy skin. Aluminum acetate (Domeboro solution) soaks can also be helpful to dry the rash and reduce itch.
  • In cases of severe or extensive rash, especially around the face or genitals, your physician may prescribe oral or injected steroids.

Do not...

  • DO NOT touch the skin or clothing of the exposed person with your bare hands, if possible, until after they have been thoroughly washed.
  • DO NOT burn poison ivy, oak, or sumac to get rid of it. The resins can be spread via smoke, and can cause severe exposures to individuals far downwind.

Call immediately for emergency medical assistance if...

  • The victim is suffering a severe allergic reaction, such as swelling and/or difficulty breathing, or has had a severe reaction to a past exposure.
  • The victim has been exposed to the smoke of a burning plant.
  • The rash covers more than one quarter of the body.

Call your physician if...

  • Itching is severe and cannot be controlled.
  • The rash affects the face, lips, eyes, or genitals.
  • The rash shows signs of infection, such as pus, yellow fluid leaking from blisters, odor, or increased tenderness.

Prevention

  • Learn to identify poison ivy, oak, and sumac, and teach your children to identify them as soon as they are able.
  • Remove these plants if they grow near your home (but never burn them).
  • Cover skin with clothing (long sleeves, long pants, shoes, and socks) when walking in the woods or in areas where these plants may grow.
  • Be aware of resins carried by pets.
  • Barrier creams, such as Ivy-Block, may offer some protection.

 

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Review Date: 4/4/2007

Reviewed By: Alan Greene, M.D., F.A.A.P., Department of Pediatrics, Packard Children's Hospital, Stanford University School of Medicine; Chief Medical Officer, A.D.A.M., Inc.


The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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