Acute
Of abrupt onset, rapidly progressive and in need of urgent care.

Allergen
A substance, foreign to the body, which can produce a hypersensitive reaction in the body.

Allergic Contact Dermatitis
A red, itchy, weepy reaction where the skin has come into contact with a substance that the immune system recognizes as foreign. This type of reaction reflects a specific sensitivity or allergy to a specific substance. Also called allergic contact eczema.

Allergic Rhinitis
A seasonal allergic, upper respiratory reaction stimulated by tree, grass or weed pollen that causes sneezing and watery, itchy eyes. Hay fever is a specific type of allergic rhinitis.

Allergy
When the body’s immune system over reacts to foreign substances. People prone to allergies are said to be allergic or atopic.

Antibody
An immunoglobulin that binds specifically to a given antigen.

Antigen
A substance that reacts with antibodies or memory T cells to give rise to an immune reaction. An antigen that binds with a specific antibody or T cell can give rise to allergy.

Antihistamine
A substance capable of reducing inflammation, swelling and other effects often experienced as an allergic reaction. It works by blocking the histamine’s effects on the tissue. It is temporary and does not actually stop the allergic reaction but merely suppresses the body’s reaction.

Asthma
A common disorder in which chronic inflammation of the bronchial tubes (bronchi) makes them swell, narrowing the airways. Breathing difficulties characterized by wheezing are a result.

Atopic
Hereditary tendency to experience immediate allergic reactions because of the presence of an antibody in the skin.

Atopic Dermatitis
A skin disease characterized by areas of severe itching, redness, scaling and loss of the skin’s surface (excoriation).

Bacteria
A class of microorganisms that cause infections.

B cells (lymphocytes)
Cells that make and carry surface immunoglobulins.

Biopsy
The removal of a tissue sample for the purpose of diagnosis.

Chronic
Long-lasting, ongoing.

Contact Dermatitis
A condition resulting from contact between skin and some substance that causes an irritation.

Contact eczema
A localized reaction that includes redness, itching and burning where the skin has come into contact with an allergen or with an irritant such as an acid, a cleaning agent or another chemical.

Corticosteroids
A class of substances related to a natural hormone that can diminish an inflammatory response such as itching or irritation of the skin.

Dandruff
A mild skin condition that produces white flakes that may be shed and fall from the hair.

Dermatitis
Inflammation of the skin, either due to direct contact with an irritating substance, or to an allergic reaction. Symptoms of dermatitis include redness, itching and, in some cases, blistering.

Dermis
The middle layer of the skin, below the epidermis and above subcutaneous tissue. It is composed of connective tissue in which is embedded hair follicles, sweat glands, superficial and deeper blood vessels and nerve fibers.

Dyshidrotic Eczema
Irritation of the skin on the palms of hands and soles of the feet characterized by clear, deep blisters that itch and burn.

Epidermis
The outermost layer of skin. The epidermis has several active zones of skin cells, including cells that participate in immune reactions. Many eczematous skin conditions are initiated in the epidermis.

Flare-ups
Sudden outbreaks.

Hay Fever
A seasonal allergy to airborne particles characterized by itchy eyes, runny nose, nasal congestion, sneezing, itchy throat and excess mucus.

Hydrocortisone
A less potent corticosteroid incorporated into creams, lotions and ointments used to treat skin inflammation.

Immediate Hypersensitivity
A pattern of immune reactivity that begins within minutes of exposure to an antigen. In the skin, immediate hypersensitivity often presents as hives.

Immunomodulation
Therapeutic manipulation of the immune system, used clinically to treat a disease in which immune system dysregulation is a factor.

Immunosuppressant
An agent that can suppress or prevent the immune response.

Irritant Contact Dermatitis
A reaction brought on purely by repeated irritation from a substance (such as water causing "dish pan hands")

Lichenification
Thickening upper layers of the skin in response to trauma, forming a crisscross pattern.

Neurodermatitis
Scaly patches of skin on the head, lower legs, wrists or forearms caused by a localized itch such as from an insect bite that becomes intensely irritated when scratched.

Nickel
A silver-white metallic element. Long-term exposure to nickel, such as from jewelry, can cause a form of contact dermatitis called nickel dermatitis.

Nummular Eczema
Coin-shaped patches of irritated skin - most common on the arms, back, buttocks and lower legs that may be crusted, scaling and extremely itchy.

Phototherapy
Treatment with light.

Pruritus
Itch.

Scaling
Abnormal shedding or accumulation of an upper layer of skin (the stratum corneum).

Seborrheic Dermatitis
A medical name for what is popularly called seborrhea.

Seborrheic Eczema
Yellowish, oily, scaly patches of skin on the scalp, face and occasionally other parts of the body.

Stasis Dermatitis
A skin irritation on the lower legs generally related to circulatory problems.

Subcutaneous Tissue
The deepest layer of skin, under the epidermis and dermis. Subcutaneous tissue is composed of fat, tissue that separates the fat in lobules (pockets), nerves and blood vessels. The fatty tissue is biologically active and subject to inflammatory processes.

Systemic Medication
Medication that circulates throughout the body and is taken orally or given by injection or infusion.

Tar Treatment
Treatment consisting of chemicals related to coal tar used topically to reduce itching. Coal Tar has been identified as a potential carcinogen.

T Cell
A white blood cell of the immune system that participates in a number of immune responses.

Topical
On the surface of the body.

Urticaria
Hives.

Vesicular
Pertaining to the presence of one or more vesicles. A vesicle is a small blister.