patch test

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.

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. ==Process== Application of the patch tests takes about half an hour, though many times the overall appointment time is longer as the provider will take an extensive history. Tiny quantities of 25 to ~150 materials (allergens) in individual square plastic or round aluminium chambers are applied to the upper back. They are kept in place with special hypoallergenic adhesive tape. The patches stay in place undisturbed for at least 48 hours. Vigorous exercise or stretching may disrupt the test. At the second appointment, usually, 48 hours later, the patches are removed. Sometimes additional patches are applied. The back is marked with an indelible black felt tip pen or another suitable marker to identify the test sites, and a preliminary reading is done. These marks must be visible at the third appointment, usually 24–48 hours later (72–96 hours after application). In some cases, reading at 7 days may be requested, especially if a special metal series is tested. Patch Testing for cosmetic and skincare products can be broken down into a variety of different categories, including the following: Human Repeat Insult Patch Testing (Sensitization and Primary Irritation) 24, 48, 72 Hour Patch Testing Cumulative Irritation Testing Repeat Open Application Testing ==See also== Skin allergy test ==References== ==External links== "Patch tests (contact allergy testing"), DermNet NZ "CPTC Labs HRIPT Patch Testing", CPTC Labs USA

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