Patch testA 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.
Poison ivyPoison ivy is a type of allergenic plant in the genus Toxicodendron native to Asia and North America. Formerly considered a single species, Toxicodendron radicans, poison ivies are now generally treated as a complex of three separate species: Toxicodendron radicans, Toxicodendron rydbergii, and Toxicodendron orientale. They are well known for causing urushiol-induced contact dermatitis, an itchy, irritating, and sometimes painful rash, in most people who touch them. The rash is caused by urushiol, a clear liquid compound in the plant's sap.
RashA rash is a change of the human skin that 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 therefore treatments for rashes, vary widely. Diagnosis must take into account such things as the appearance of the rash, other symptoms, what the patient may have been exposed to, occupation, and occurrence in family members.
HypersensitivityHypersensitivity (also called hypersensitivity reaction or intolerance) is an abnormal physiological condition in which there is an undesirable and adverse immune response to antigen. It is an abnormality in the immune system that causes immune diseases including allergies and autoimmunity. It is caused by many types of particles and substances from the external environment or from within the body that are recognized by the immune cells as antigens.
BlisterA blister is a small pocket of body fluid (lymph, serum, plasma, blood, or pus) within the upper layers of the skin, usually caused by forceful rubbing (friction), burning, freezing, chemical exposure or infection. Most blisters are filled with a clear fluid, either serum or plasma. However, blisters can be filled with blood (known as "blood blisters") or with pus (for instance, if they become infected). The word "blister" entered English in the 14th century.
Urushiol-induced contact dermatitisUrushiol-induced contact dermatitis (also called Toxicodendron dermatitis or Rhus dermatitis) is a type of allergic contact dermatitis caused by the oil urushiol found in various plants, most notably sumac family species of the genus Toxicodendron: poison ivy, poison oak, poison sumac, and the Chinese lacquer tree. The name is derived from the Japanese word for the sap of the Chinese lacquer tree, urushi.
DermatitisDermatitis is inflammation of the skin, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened. The area of skin involved can vary from small to covering the entire body. Dermatitis is often called eczema, and the difference between those terms is not standardized. The exact cause of the condition is often unclear. Cases may involve a combination of allergy and poor venous return.
Aroma compoundAn aroma compound, also known as an odorant, aroma, fragrance or flavoring, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently volatile for transmission via the air to the olfactory system in the upper part of the nose. As examples, various fragrant fruits have diverse aroma compounds, particularly strawberries which are commercially cultivated to have appealing aromas, and contain several hundred aroma compounds.
Atopic dermatitisAtopic dermatitis (AD), also known as atopic eczema, is a long-term type of inflammation of the skin (dermatitis). It results in itchy, red, swollen, and cracked skin. Clear fluid may come from the affected areas, which can thicken over time. AD may also simply be called eczema, a term that generally refers to a larger group of skin conditions. Atopic dermatitis affects about 20% of people at some point in their lives. It is more common in younger children. Females are slightly more affected than males.
HivesHives, also known as urticaria, is a kind of skin rash with red, raised, itchy bumps. Hives may burn or sting. The patches of rash may appear on different body parts, with variable duration from minutes to days, and does not leave any long-lasting skin change. Fewer than 5% of cases last for more than six weeks. The condition frequently recurs. Hives frequently occur following an infection or as a result of an allergic reaction such as to medication, insect bites, or food.
