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" Listed below are the most commonly used tests in dermatology. RAST test A RAST (radioallergosorbent) test is a blood test used to investigate increased sensitivity to a variety of food groups (eg eggs, cows&amp;#039; milk and nuts), house dust mite and animal dander (hair or fur). It&amp;#039;s often used in the investigation of patients with atopic eczema. A person can have a degree of sensitivity to all these things, but not all may be responsible for worsening of their eczema. This can make the results difficult to interpret.  It is most useful for children under five, particularly where there is a history of intolerance to certain foods. Avoidance of these foods can lead to a marked improvement of their eczema. Prick testing This is a specialist test used for the investigation of immediate (Type 1) sensitivity to things that come into contact with the skin.  This sensitivity usually appears as a sudden onset of itchy &amp;#039;hives&amp;#039; on the skin, sometimes with swelling around the mouth and wheeziness. The test is used for the investigation of latex allergy. Latex is mainly found in thin rubber gloves used in hospitals or by dentists, and it&amp;#039;s also found in balloons and condoms. The test consists of putting a number of substances on the arm in various strengths and introducing them into the skin with a very fine needle. After approximately 10 minutes, each area tested is assessed to see whether a red patch has developed. Patch testing This is used in the investigation of allergic contact dermatitis.  It&amp;#039;s mainly used where eczema is confined to a specific site, for example, only the hands or the face. Eczema which is worsening or failing to respond to conventional treatment should also be investigated in this way. A person&amp;#039;s occupation is important in determining which substances to test for. Patients for the patch testing clinic are usually asked to come along for three visits in one week.  First visit This is when the consultant decides which tests to use. Patients are also asked to bring along products that they use regularly and feel may be aggravating their skin, because often these can be tested as well. The substances are placed in small metal chambers and stuck on to the back, and the area must be kept dry for two days. Second visit On the second visit the patches are removed. Often, the consultant will have a first look for any reactions and apply any additional patches that may be relevant. Third visit On the third visit, the patch tests are formally read, because it takes about four days for a reaction to show up. A red, raised itchy patch indicates an allergy to a particular substance. The consultant can then give information about products that contain this substance (allergen) and explain how to avoid them. Unfortunately, avoidance of a proven allergen doesn&amp;#039;t always completely clear the eczema, particularly if it is on the hands. Negative patch tests are helpful because they can make a diagnosis of irritant contact eczema more likely, and it can be treated accordingly. Other people also read: Eczema: What is eczema? Moisturisers: Find out how moisturisers work. Newer medicines: What are the possible side-effects? Topical corticosteroids: Why are there different strengths of corticosteroids? Last updated 01.05.2014 "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.netdoctor.co.uk/conditions/skin-and-hair/a3658/allergy-tests/>