IMMUNE SYSTEMcalled a HYPERSENSITIVITY REACTION.
For reasons researchers do not fully understand,
the immune system produces antibodies for the
substance that result in the IMMUNE RESPONSEper-
ceiving the substance as a foreign invader. When
the allergen contacts or enters the body, the anti-
bodies attack it. Nearly any substance can be an
allergen. DESENSITIZATIONis a treatment for allergies
that exposes the person to progressive doses of the
allergen to increase the body’s tolerance for the
presence of the allergen and diminish the hyper-
sensitivity reaction.
COMMON ALLERGENSalmonds animal dander aspirin (salicylates)
bee stings cashews cockroaches
dust and dust mites eggs fish
fragrances and perfumes fungi grasses
lanolin latex milk
molds nickel peanuts
pecans penicillin pollens
shellfish smoke strawberries
SOY sulfa wheat
See also ALLERGY; ALLERGY TESTING; ANAPHYLAXIS;
ANTIBODY; ANTIGEN; ASTHMA; LIVING WITH ALLERGIES;
MULTIPLE CHEMICAL SENSITIVITY SYNDROME.
allergic asthma A HYPERSENSITIVITY REACTION
(allergic reaction) that involves the airways
(bronchi). allergic ASTHMA is a type I or
IMMUNOGLOBULINE (IgE) reaction. Mast cells in the
bronchial membranes release HISTAMINE, PROSTA-
GLANDINS, and LEUKOTRIENES. These substances
cause itching and swelling of the bronchial mem-
branes, resulting in wheezing and the sensation of
chest tightness.
Cockroach droppings are the most frequent
cause of allergic asthma. Other common allergens
for allergic asthma include pollens (trees, grasses,
and weeds), dust and dust mites, cigarette smoke,
molds, and pet dander (especially cat dander).
About 70 percent of people who have allergic
asthma also have ALLERGIC RHINITIS, also called sea-
sonal allergies or hay FEVER.
The diagnostic path focuses on separating aller-
gic from nonallergic asthma. Though the symp-
toms are the same, the mechanisms and treatment
approaches are different. Symptoms of allergic
asthma include wheezing, shortness of breath
(DYSPNEA), sensation of being unable to get enough
air, and coughing. A severe hypersensitivity
reaction, ANAPHYLAXIS, may occur if the bronchi
swell enough to prevent the flow of air into the
LUNGS.ANAPHYLAXISis a potentially life-threat-
ening condition that requires immedi-
ate care from a doctor or hospital
emergency department.Treatment for allergic asthma may include oral
and inhaled ANTIHISTAMINE MEDICATIONS, cortico-
steroid medications, and leukotriene receptor
antagonist medications. Omalizumab (Xolair), a
monoclonal antibody administered via subcuta-
neous injection, dramatically drops IgE levels in
the BLOOD circulation, effectively stopping the
hypersensitivity reaction before it causes symp-
toms. The most effective treatment is avoiding
known or suspected allergens, though this is not
always possible. ALLERGY TESTINGcan determine the
specific allergens responsible for symptoms.
DESENSITIZATION, in which the allergist exposes the
person to small but increasing doses of the aller-
gen over time, can help reduce the immune
response to the allergen.
See alsoALLERGIC CONJUNCTIVITIS; ALLERGIC DER-
MATITIS; ALLERGY; ANTIGEN; ATOPY; BREATH SOUNDS;
CYTOKINES; LIVING WITH ALLERGIES; MONOCLONAL ANTI-
BODIES(MABS).allergic conjunctivitis A type I (IMMUNOGLOBULIN
E [IgE]) HYPERSENSITIVITY REACTION, commonly
called an allergic reaction, that affects the mem-
branes that line the inner eyelids (conjunctiva).
Sometimes the irritation also reddens the white
part of the eye (sclera). Allergic CONJUNCTIVITISfea-
tures red and swollen conjunctiva with excessive
tearing and itching of the eyes and sometimes a
white discharge. PHOTOPHOBIA(heightened sensi-
tivity to light) is common. Because these symp-
toms also suggest viral or bacterial conjunctivitis
(pink eye), which are infections, particularly
when the discharge is yellow or green, a doctor
should examine the eyes and assess the symptoms
to make the correct diagnosis. Treatment differs
according to the cause.240 The Immune System and Allergies