Skin allergy test - AbsoluteAstronomy.com

Skin allergy testing is a method for medical diagnosis of allergies

Allergy

An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...

that attempts to provoke

Provocation (medical)

A provocation test, also called a provocation trial or provocation study, is a form of clinical trial whereby participants are exposed to either a substance or "thing" that is claimed to provoke a response, or to a sham substance or device that should provoke no response. An example of a...

a small, controlled, allergic response.

Process

A microscopic amount of an allergen

Allergen

An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....

is introduced to a patient's skin by various means:

Prick test or scratch test: pricking the skin with a needle or pin containing a small amount of the allergen.
Patch test: applying a patch to the skin, where the patch contains the allergen

If an immuno-response is seen in the form of a rash

Rash

A rash is a change of the skin which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell and may be painful. The causes, and...

, urticaria

Urticaria

Urticaria is a kind of skin rash notable for pale red, raised, itchy bumps. Hives is frequently caused by allergic reactions; however, there are many non-allergic causes...

(hives), or (worse) anaphylaxis

Anaphylaxis

Anaphylaxis is defined as "a serious allergic reaction that is rapid in onset and may cause death". It typically results in a number of symptoms including throat swelling, an itchy rash, and low blood pressure...

it can be concluded that the patient has a hypersensitivity

Hypersensitivity

Hypersensitivity refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. These reactions may be damaging, uncomfortable, or occasionally fatal. Hypersensitivity reactions require a pre-sensitized state of the host. The four-group classification...

(or allergy

Allergy

) to that allergen

Allergen

An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....

. Further testing can be done to identify the particular allergen.

The "scratch test" as it's called, is still very commonly used as an allergen test. A similar test involving injecting the allergen is also used, but is not quite as common due to increased likelihood of infection and general ineffectiveness by comparison. There are other methods available to test for allergy

Allergy

.

Some allergies are identified in a few minutes but others may take several days. In all cases where the test is positive, the skin will become raised, red and appear itchy. The results are recorded- larger wheals indicating that the subject is more sensitive to that particular allergen. A negative test does not mean that the subject is not allergic; simply that either the right concentration was not used or the body failed to elicit a response.

Prick test

In the prick (scratch) test, a few drops of the purified allergen are gently pricked on to the skin surface, usually the forearm. This test is usually done in order to identify allergies to pet dander

Dander

Dander is an informal term for a material shed from the body of various animals, similar to dandruff. It may contain scales of dried skin and hair, or feathers. It is a cause of allergies in humans....

, dust, pollen

Pollen

Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...

, foods or dust mites. Intradermal injections are done by injecting a small amount of allergen just beneath the skin surface. The test is done to assess allergies to drugs like penicillin

Penicillin

Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....

or bee venom.

To ensure that the skin is reacting in the way it is supposed to, all skin allergy tests are also performed with proven allergens like histamine

Histamine

Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...

or glycerin. The majority of people do react to histamine or glycerin. If the skin does not react to these allergens then it most likely will not react to the other allergens. These results are interpreted as falsely negative.

Patch test

The patch test simply uses a large patch which has different allergens on it. The patch is applied onto the skin, usually on the back. The allergens on the patch include latex, medications, preservatives, hair dyes, fragrances, resins and various metals. When a patch is applied the subject should avoid bathing or exercise for at least 48 hours.

Skin end point titration

Also called an intra dermal test, this skin end point titration (SET) uses intradermal injection of allergens at increasing concentrations to measure allergic response. To prevent a severe allergic reaction, the test is started with a very dilute solution. After 10 minutes, the injection site is measured to look for growth of wheal, a small swelling of the skin. Two millimeters of growth in 10 minutes is considered positive. If 2 mm of growth is noted, then a second injection at a higher concentration is given to confirm the response. The end point is the concentration of antigen that causes an increase in the size of the wheal followed by confirmatory whealing. If the wheal grows larger than 13 mm, then no further injection are given since this is considered a major reaction.

Blotting Paper method
Staedelar (in 1847)used method BLOTTING PAPER STRIPS to examine effect of Anacardeium.He applied sap of this plant to lower part of skin.A piece of blotting paper previously dipped in same material was applied to same side.
After 15 minute patient experienced a burning sensation which increased rapidly and reached at climax in about half hour.Skin under blotting paper turned white while surrounding areas had marked redness.
Over might skin become covered by tiny vesicles,wound healed after about two weeks.

Preparation

There are no major preparations required for skin testing. At the first consult, the subject's medical history is obtained and physical examination is performed. All consumers should bring a list of their medications because some may interfere with the testing. Other medications may increase the chance of a severe allergic reaction. Medications that commonly interfere with skin testing include the following:

Histamine antagonist
Histamine antagonist
A histamine antagonist, commonly referred to as antihistamine, is a pharmaceutical drug that inhibits action of histamine by blocking it from attaching to histamine receptors.- Clinical effects :...

s like Allegra, Claritin, Benadryl
Benadryl
Benadryl is a brand name allergy medicine marketed over-the-counter by Johnson & Johnson subsidiary McNeil Consumer Healthcare. Prior to 2007, Benadryl was marketed by Pfizer Consumer Healthcare...

, Zyrtec
Antidepressant
Antidepressant
An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia and anxiety disorders such as social anxiety disorder. According to Gelder, Mayou &*Geddes people with a depressive illness will experience a therapeutic effect to their mood;...

s like Amitriptyline
Amitriptyline
Amitriptyline is a tricyclic antidepressant . It is the most widely used TCA and has at least equal efficacy against depression as the newer class of SSRIs...

, Doxepin
Doxepin
Doxepin is a psychotropic agent with tricyclic antidepressant and anxiolytic properties, known under many brand-names such as Aponal, the original preparation by Boehringer-Mannheim, now part of the Roche group; Adapine, Doxal , Deptran, Sinquan and Sinequan...
Antacid
Antacid
An antacid is a substance which neutralizes stomach acidity.-Mechanism of action:Antacids perform a neutralization reaction, increasing the pH to reduce acidity in the stomach. When gastric hydrochloric acid reaches the nerves in the gastrointestinal mucosa, they signal pain to the central nervous...

like Tagamet or Zantac

Consumers who undergo skin testing should know that anaphylaxis

Anaphylaxis

can occur anytime. So if any of the following symptoms are experienced, a physician consultation is recommended immediately:

Low grade Fever
Lightheadedness or dizziness
Wheezing or Shortness of breath
Extensive skin rash
Swelling of face, lips or mouth
Difficulty swallowing or speaking

Contraindications

Even though skin testing may sound like a benign procedure it does have some risks which include swollen red bumps (hives) may occur after the test. The hives usually disappear in a few hours after the test. In rare cases they can persist for a day or two. These hives may be itchy and are best treated by applying an over the counter hydrocortisone cream.
In very rare cases one may develop a full blown allergic reaction. Physicians who perform skin test always have equipment and medications available in case an anaphylaxis reaction occurs. This is the main reason why consumers should not get skin testing performed at corner stores or by people who have no medical training.

Skin testing can be done on individuals of all ages. However, there are times when a skin test should not be done. Individuals who take medications for depression, gastric acidity or antihistamines should not undergo this test. In such cases, stopping the medications for a skin test may not be worthwhile as one may develop symptoms from the untreated medical disorders. Individuals who have severe, generalized skin disease or an acute skin infection should not undergo skin testing. One needs uninvolved skin for testing.

There are some individuals who are highly sensitive to even the smallest amount of allergen and in such scenarios, allergic testing is not recommended. Whenever the chances of an anaphylactic shock are high, the test is best avoided.

Besides skin tests, there are blood tests which measure a specific antibody

Antibody

An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...

in the blood. The IgE

IGE

IGE was one of the largest services company buying and selling virtual currencies and accounts for MMORPG. During its peak time, it had offices in Los Angeles, China , and headquarters & customer service centre in Hong Kong. IGE was one of the main monopoly in virtual economy services, also known...

antibody plays a vital role in allergies but its levels in blood do not always correlate with the allergic reaction.

There are many alternative health care practitioners who perform a variety of provocation neutralization tests, but the vast majority of these tests have no validity and have never been proven to work scientifically.

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Process

Prick test

Patch test

Skin end point titration

Preparation

Contraindications

See also

External links