allergy skin test A test in which a small drop of the suspected allergy-provoking substance (allergen) is placed on the skin and the skin is then gently scratched through the drop with a sterile needle. If the skin reddens and, more importantly, if it swells, the test is read as positive, and allergy to that…
allergy to cockroaches An allergic reaction to tiny protein particles shed or excreted by cockroaches. Asthma can be due to exposure to cockroach allergens. Removing cockroach allergens from the home is not an easy job, but it can go far in reducing the frequency and severity of asthma and other allergic reactions.
allograft The transplant of an organ or tissue from one individual to another of the same species with a different genotype. For example, a transplant from one person to another, but not an identical twin, is an allograft. Allografts account for many human transplants, including those from cadaveric, living related, and living unrelated donors. Also…
allopath A term sometimes applied to a physician who practices allopathy, or conventional medicine. See also allopathy.
allopathic medicine See allopathy.
allopathy The system of medical practice that treats disease by the use of remedies to produce effects different from those produced by the disease under treatment. Doctors of medicine (MDs) practice allopathic medicine. The term “allopathy” was coined to designate conventional medicine as opposed to homeopathy, the system of therapy based on the concept that…
alopecia Baldness. Temporary alopecia may occur as a result of chemotherapy. Permanent alopecia may result from any of several conditions, including common male-pattern baldness. Radiation therapy administered to the head can also cause permanent alopecia due to irreversible damage to the hair follicles. See also alopecia areata; alopecia capitis totalis; alopecia universalis; alopecia, traumatic.
alopecia, traumatic Hair loss caused by injury to the scalp. Common causes include the use of caustic hair straighteners, especially those that include lye as an ingredient; stress traction injury from tight rollers and braiding; overheating of the hair shafts; and compulsive pulling out of hair (trichotillomania).
albinism A pigmentation disorder characterized by partial or total lack of the pigment melanin in the skin, hair, and iris. Albinism is caused by an autosomal recessive gene and can occur in people of any ethnic background. People with albinism have delicate skin that sunburns and develops skin cancer easily, and they may suffer from…
albino A person with albinism. The term was first applied by the Portuguese to people in West Africa, who may have had partial or complete albinism.
albuginea Tough white fibrous tissue. The tunica albuginea of the testis, for example, is the layer of dense whitish inelastic tissue that surrounds the testis.
albumin The main protein in human blood and the key to regulating the osmotic pressure of blood. Chemically, albumin is soluble in water, precipitated by acid, and coagulated by heat.