A substance that can produce a hypersensitive reaction in the body.
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
A drug with the ability to kill bacteria.
An immunoglobulin that binds specifically to a given 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
respiratory disorder characterized by breathing trouble (wheezing).
tendency to experience immediate allergic reactions because of the
presence of an antibody in the skin.
A class of microorganisms that cause infections.
B cells (lymphocytes):
Cells that make and carry surface immunoglobulins.
Removing a section of skin so it can be examined under a microscope.
studies of new treatments, new uses of existing treatment, or new
screening methods to detect disease.
Capable of being transmitted from person to person.
Corticosteroids: A class of substances related to a natural
hormone that can diminish an inflammatory response such as itching
or irritation of the skin.
A powerful prescription drug that decreases the body’s immune
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.
Making soft or supple; soothing especially to the skin or mucous
One liquid is
suspended in a second liquid because the first cannot be mixed with
the second, such as oil and water.
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.
Hydrocortisone: A less potent corticosteroid incorporated
into creams, lotions and ointments used to treat skin inflammation.
Hyperirritability: Easily irritated.
Human leucocyte antigen (HLA):
Any human Class I and Class II major histocompatability complex (MHC)
protein. These are important in presenting antigens to immune
A pattern of immune reactivity that begins within minutes of
exposure to an antigen. Immediate reactivity is mediated primarily
by mast cells. In the skin, immediate hypersensitivity often
presents as hives.
The body’s natural defense against foreign substances and organisms
that could lead to illness.
The signs and symptoms of reactions of immune cells or antibodies to
An antigen-binding protein secreted by specific white cells of
the immune system. Immunoglobulins are antibodies.
Therapeutic manipulation of the immune system, used clinically to
treat a disease in which immune system dysregulation is a factor.
consent: The process by
which a volunteer for a clinical trial agrees to participate after
being fully informed regarding purposes of the trial, risks and
benefits associated with participation in the trial, and whether
volunteers will be randomized to receive treatment or placebo.
Existing in a person from birth.
Agents that may produce inflammation if exposure is sufficient.
Lichenification: Thickening upper layers of the skin in
response to trauma.
Major histocompatability complex (MHC):
A specific cluster of genes that encode proteins involved in immune
system reactions. See Human leucocyte antigen.
A tissue cell that is a primary
participant in immediate hypersensitivity reactions. Mast
cells make and release histamine and other mediators of
The chemical compound produced when the body breakdowns a drug.
Treatment with light.
A pharmacologically inactive
substance with no medicinal value, used as method for "control" in
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.
Medication that circulates throughout the body and is taken orally
or given by injection or infusion.
Treatment consisting of chemicals related to coal tar used topically
to reduce itching.
T cell: A white blood
cell of the immune system that participates in a number of immune
Tolerance: A state
of immunologic unresponsiveness to a substance that would otherwise
provoke an immune response.
On the surface of the body.
All content solely
developed by the American Academy of Dermatology