A skin test is a check for immediate allergic reactions to as many as 50 different substances at once. This test is usually done to identify allergies to pollen, mold, pet dander, dust mites, and foods. Skin tests may be done to diagnose rashes, moles, skin allergies, food allergies, bacterial or fungal skin infections, and other diseases. Skin tests are also done to tell the difference between cancer (malignant) cells and noncancer (benign) growths.
Types of Test
- The Casoni test – is a skin test used in the diagnosis of hydatid disease. The test involves the intradermal injection of 0.25 ml of sterilized fluid from hydatid cysts/human cysts and sterilized by Seitz filtration on the forearm and an equal volume of saline injected on the other forearm. Observations were made for the next 30 mins and after 1 to 2 days.[rx] A wheal response occurring at the injection site within 20 minutes is considered positive (immediate hypersensitivity). Delayed hypersensitivity reactions are usually read after 18-24 hours.[rx] The test is positive in about 90% of cases of hydatid disease affecting the liver, but positive in less than 50% of patients with hydatid disease elsewhere in the body; false-positive results are also common. Being a type I hypersensitivity reaction, an anaphylactic reaction tray must be kept ready before carrying out the test.[rx] Consequently, serological tests are now generally used.[rx] The test was described in 1912 by Tomaso Casoni.[rx]
- Corneometry – is a widely practiced method for the measurement of skin hydration. It uses a capacitive sensor to measure the relative permittivity of upper skin layers. Because these depend on the hydration of skin, the measured value is a measure for skin hydration.[rx] The name corneometry is derived from the German trademark Corneometer.[rx] In 1979 the first commercial instrument for measuring skin hydration was sold under this name.
- The Fernandez reaction – is a reaction that occurs to signal a positive result in the lepromin skin test for leprosy.[rx] The reaction occurs in the skin at the site of injection if the body possesses antibodies to the Dharmendra antigen, one of the antigens found in Mycobacterium leprae, the bacteria that causes leprosy. The reaction occurs via a delayed-type hypersensitivity mechanism. This reaction occurs within 48 hours of injection of lepromin and is seen in only tuberculoid forms of leprosy. In contrast, the Mitsuda reaction (delayed granulomatous lesion) occurs 3–4 weeks after injection of lepromin and is only seen in patients with the tuberculoid form of leprosy (not the lepromatous form, in which the body does not mount a strong response against the bacterium). In terms of mechanism of action and appearance, the reaction is similar to the tuberculin reaction of a positive Mantoux test for tuberculosis.[rx]
- The Frei test – was developed in 1925 by Wilhelm Siegmund Frei, a German dermatologist, to identify lymphogranuloma venereum. Antigen made from sterile pus aspirated from previously unruptured abscesses produced a reaction in patients with lymphogranuloma venereum when injected intradermally. Other sources of antigen have been explored, most deriving from various tissues of mice infected with Chlamydia. The test is no longer used but stands as a milestone in our understanding of immunology. A heat-inactivated LGV 0.1ml grown in the yolk sac of the embryonated egg is injected intradermally on the forearm and a control material is prepared from a noninfected yolk sac on the other forearm i.e. control. After 48–72 hours, an inflammatory nodule more than 6mm in diameter develops at the test site.
- The hair perforation test – also known as an in vitro hair perforation test, is a laboratory test used to help distinguish the isolates of dermatophytes, such as Trichophyton mentagrophytes and its variants.[rx] The test is performed by placing an organism into a Petri dish containing water, yeast extract, and hair. The Mayo Clinic’s mycology laboratory has identified five common dermatophytes; Microsporum gypseum, Microsporum canis, Trichophyton rubrum, Trichophyton mentagrophytes, and Trichophyton tonsurans.[rx]
- The Kim test, Nickerson-Kveim, or Kveim-Siltzbach test – is a skin test used to detect sarcoidosis, where part of a spleen from a patient with known sarcoidosis is injected into the skin of a patient suspected to have the disease. If noncaseating granulomas are found (4–6 weeks later), the test is positive. If the patient has been on treatment (e.g. glucocorticoids), the test may be false negative. The test is not commonly performed, and in the UK no substrate has been available since 1996. There is a concern that certain infections, such as bovine spongiform encephalopathy, could be transferred through a Kveim test.[rx] It is named for the Norwegian pathologist Morten Ansgar Kim, who first reported the test in 1941 using lymph node tissue from sarcoidosis patients.[rx][rx] It was popularised by the American physician Louis Siltzbach, who introduced a modified form using spleen tissue in 1954.[rx] Kim’s work was a refinement of earlier studies performed by Nickerson, who in 1935 first reported on skin reactions in sarcoid.[rx] A Kim test may be used to distinguish sarcoidosis from conditions with otherwise indistinguishable symptoms such as berylliosis.[rx]
- The leishmania skin test (LST) – also called the Montenegro test, is an immunologic skin test that measures delayed-type hypersensitivity to Leishmania antigen.[rx][rx] It can be used for the diagnosis of cutaneous leishmaniasis.[rx] It was first described by Brazilian physician João Montenegro in 1926.[rx]
- The lepromin skin test – is used to determine what type of leprosy a person is infected with. It involves the injection of a standardized extract of the inactivated “leprosy bacillus” (Mycobacterium leprae or “Hansen’s bacillus”) under the skin. It is not recommended as a primary mode of diagnosis.[rx]
- A patch test – is a diagnostic method used to determine which specific substances cause allergic inflammation of a patient’s skin. Patch testing helps identify which substances may be causing a delayed-type allergic reaction in a patient and may identify allergens not identified by blood testing or skin prick testing. It is intended to produce a local allergic reaction on a small area of the patient’s back, where the diluted chemicals were planted. The chemicals included in the patch test kit are the offenders in approximately 85–90 percent of contact allergic eczema and include chemicals present in metals (e.g., nickel), rubber, leather, formaldehyde, lanolin, fragrance, toiletries, hair dyes, medicine, pharmaceutical items, food, drink, preservative, and other additives.
- The Schick test – developed in 1913,[rx] is a skin test used to determine whether or not a person is susceptible to diphtheria.[rx] It was named after its inventor, Béla Schick (1877–1967), a Hungarian-born American pediatrician
- Skin allergy testing – comprises a range of methods for medical diagnosis of allergies that attempts to provoke a small, controlled, allergic response.
- Sweat diagnostics – is an emerging non-invasive technique used to provide insights into the health of the human body. Common sweat diagnostic tests include testing for cystic fibrosis[rx] and illicit drugs.[rx] Most testing of human sweat is in reference to the eccrine sweat gland which in contrast to the apocrine sweat gland, has a lower composition of oils.[rx] Although sweat is mostly water,[rx] there are many solutes that are found in sweat that have at least some relation to biomarkers found in the blood. These include: sodium (Na+), chloride (Cl−), potassium (K+), ammonium (NH+ 4), alcohols, lactate, peptides & proteins.[rx][rx] The development of devices, sensing techniques and biomarker identification in sweat continues to be an expanding field for medical diagnostics and athletics applications.
- The sweats test – measures the concentration of chloride that is excreted in sweat. It is used to screen for cystic fibrosis (CF).[1] Due to defective chloride channels (CFTR), the concentration of chloride in the sweat is elevated in individuals with CF.
- The tine test – is a multiple-puncture tuberculin skin test used to aid in the medical diagnosis of tuberculosis (TB). The tine test is similar to the Heaf test, although the Mantoux test is usually used instead. There are multiple forms of the tine tests which usually fall into two categories: the old tine test (OT) and the purified protein derivative (PPD) tine test. Common brand names of the test include Aplisol, Aplitest, Tuberculin PPD TINE TEST, and Tubersol.[rx]
- Transepidermal water loss (TEWL or TWL) – is the loss of water that passes from inside a body (animal or plant) through the epidermis (that is, either the epidermal layer of animal skin or the epidermal layer of plants) to the surrounding atmosphere via diffusion and evaporation processes. TEWL in mammals is also known as insensible water loss (IWL), as it is a process over which organisms have little physiologic control and of which they are usually mostly unaware. Insensible loss of body water can threaten fluid balance; in humans, substantial dehydration sometimes occurs before a person realizes what is happening.
