Editing Allergy (section)

===Skin prick testing===
<!-- Hidden text, as this links back to the same page, restore when main article is created - {{Main|Skin Test|l1=Skin testing}}-->
[[File:Allergy skin testing.JPG|thumb|right|Skin testing on arm]]
[[File:Skintest2.jpg|thumb|right|Skin testing on back]]
[[Skin test]]ing is also known as "puncture testing" and "prick testing" due to the series of tiny punctures or pricks made into the patient's skin. Tiny amounts of suspected allergens and/or their [[extracts]] (''e.g.'', pollen, grass, mite proteins, peanut extract) are introduced to sites on the skin marked with pen or dye (the ink/dye should be carefully selected, lest it cause an allergic response itself). A negative and positive control are also included for comparison (eg, negative is saline or glycerin; positive is histamine). A small plastic or metal device is used to puncture or prick the skin. Sometimes, the allergens are injected "intradermally" into the patient's skin, with a needle and syringe. Common areas for testing include the inside forearm and the back.

If the patient is allergic to the substance, then a visible inflammatory reaction will usually occur within 30&nbsp;minutes. This response will range from slight reddening of the skin to a full-blown [[Urticaria|hive]] (called "wheal and flare") in more sensitive patients similar to a [[mosquito bite]]. Interpretation of the results of the skin prick test is normally done by allergists on a scale of severity, with +/− meaning borderline reactivity, and 4+ being a large reaction. Increasingly, allergists are measuring and recording the diameter of the wheal and flare reaction. Interpretation by well-trained allergists is often guided by relevant literature.<ref name="pmid16164451"/>

In general, a positive response is interpreted when the wheal of an antigen is ≥3mm larger than the wheal of the negative control (eg, saline or glycerin).<ref>{{Cite web |title=Appropriate use of allergy testing in primary care - Best Tests December 2011 |url=https://bpac.org.nz/BT/2011/December/allergy-testing.aspx#:~:text=If%20the%20diameter%20of%20the,the%20age%20of%20the%20individual. |access-date=2024-04-19 |website=bpac.org.nz}}</ref> Some patients may believe they have determined their own allergic sensitivity from observation, but a skin test has been shown to be much better than patient observation to detect allergy.<ref name="pmid11101180" />

If a serious life-threatening anaphylactic reaction has brought a patient in for evaluation, some allergists will prefer an initial blood test prior to performing the skin prick test. Skin tests may not be an option if the patient has widespread skin disease or has taken [[antihistamines]] in the last several days.