tions are the most effective measures for protect-
ing the chemosenses. Subclinical sinusitis (ongo-
ing sinus infection that does not have symptoms),
structural defects of the nose (such as nasal polyps
and septal deviation), and allergic rhinitis are the
most common causes of disturbances involving
these senses. Most are correctable, which nearly
always restores smell and taste. Other efforts
include reducing exposure to cigarette smoke,
industrial pollutants, and inhaled drugs such as
cocaine. Unfortunately age-related diminishment
is permanent. Most people with smell and taste
disturbances can learn methods to accommodate
the diminished perception of flavor with season-
ings (other than salt and sugar) to enhance foods
and beverages.
See also AGING, OTOLARYNGOLOGICAL CHANGES THAT
OCCUR WITH; NASAL POLYP; SJÖGREN’S SYNDROME;
SMOKING AND HEALTH.
sneeze A REFLEX that forcefully expels air
through the NOSE. A sneeze originates with an irri-
tation to the mucous membranes in the nose,
sometimes perceptible as a tickling sensation and
other times not noticeable, that activates NERVE
impulses. The fifth cranial nerve (trigeminal
nerve) carries the impulse to a cluster of special-
ized neurons (nerve cells) in the brainstem (the
part of the BRAINthat regulates the body’s basic
vital functions including reflexes). Scientists call
this area the sneeze center, though they do not
know its precise location because it is not physi-
cally distinct from other portions of the brainstem.
The sneeze center sends nerve signals back to the
body through numerous nerve pathways that acti-
vate a coordinated response.
A sneeze results when the brainstem signals the
VOCAL CORDSto close, allowing air pressure to build
in the airway, then signals the DIAPHRAGMand vari-
ous muscles in the chest, THROAT, and face to con-
tract and the vocal cords to open. This sequence of
events expels air through the nose with great
force; researchers have measured sneezes leaving
the nose at the equivalent of 100 miles per hour.
The pressure blows mucus and irritants from the
nose.
When the irritation stops, the cycle of the
sneeze reflex ends. People who have a health con-
dition such as SINUSITISor ALLERGIC RHINITISmay
sneeze so often that their noses become raw and
irritated. Nasal sprays containing decongestants
help reduce swelling of the nasal passages; those
containing antihistamines help subdue the nose’s
local reaction to allergens. These approaches are
often effective in reducing sneezing episodes.
Increasing the moisture content of the nasal
mucosa, such as by BREATHINGhumidified air and
drinking plenty of fluids, helps relieve irritation.
Many viruses, such as those that cause COLDS
and INFLUENZA, have adapted their structures to
take advantage of the sneeze mechanism, using it
to disperse themselves to new hosts. To reduce the
spread of these infections, health experts recom-
mend sneezing into disposable tissues and discard-
ing them, then washing the hands thoroughly
with soap and water.
Some people sneeze when they step into sun-
light or look up at a sunlit sky, called photic sneez-
ing. Doctors do not know why photic sneezing
occurs, though it is an inherited trait. Some
researchers speculate that sunlight (or any very
bright light) stimulates brain activity near the
brain’s sneeze center, which sends the message to
the body to sneeze. About one in four people
experiences photic sneezing.
See also BAROTRAUMA; BLOWING THE NOSE; CRANIAL
NERVES; HAND WASHING; NASAL VESTIBULITIS; SNEEZE/
COUGH ETIQUETTE; VIRUS.sore throat See PHARYNGITIS.speech disorders Conditions that affect the abil-
ity of structures of the MOUTHand THROATto form
the sounds necessary for speech. Health-care
providers often refer to these conditions as disor-
ders of articulation to distinguish them from
LEARNING DISORDERSthat may affect speech. Learn-
ing disabilities typically involve BRAIN function,
whereas speech or articulation disorders involve
the mechanics of speech.
Many speech disorders arise from structural
anomalies that become apparent during early
childhood, such as CLEFT PALATE/CLEFT PALATE AND
LIP, incorrect placement of the TEETHas they erupt,
or deviations in the size and shape of the oral cav-
ity. Functional difficulties, such as tongue control
and lip placement during articulation, may also
cause or contribute to speech disorders. HEARING54 The Ear, Nose, Mouth and Throat