Webster's New World Medical Dictionary

anaerobic
Not requiring oxygen. Anaerobic bac-
teria, for example, do not require oxygen to grow.
anal fissure
A tear in the anal canal, one of the
most common causes of red blood in the stool.
anal itching
Irritation of the skin at the exit of
the rectum, accompanied by the desire to scratch.
The intensity of anal itching is increased by mois-
ture, pressure, and abrasion caused by clothing and
sitting. It may be caused by irritating chemicals in
food (as in spices, hot sauces, and peppers); irrita-
tion due to frequent liquid stools, as in diarrhea;
diseases, such as diabetes mellitus or HIV infection,
that increase the possibility of yeast infections; and
psoriasis. Other causes of anal itching include hem-
orrhoids, anal fissures, abnormal local growth of
anal skin (anal papillae), and skin tags. Treatment
is directed first toward relieving the burning and
soreness, including cleaning and drying the anus
thoroughly, avoiding leaving soap in the anal area,
showering gently without directly rubbing or irritat-
ing the skin, and using moist pads rather than toilet
paper to clean the anus after bowel movements.
Local application of cortisone cream may help. Also
known as pruritus ani.
analgesia
The inability to feel pain.
analgesic
A drug that relieves pain.
analysis
In psychology, a term for conversation-
based therapeutic processes used to gain under-
standing of complex emotional or behavioral issues.
anaphylactic shock
A widespread and extremely
serious allergic reaction that can result in death.
Symptoms include dizziness, loss of consciousness,
labored breathing, swelling of the tongue and
breathing tubes, blueness of the skin, low blood
pressure, and heart failure. Immediate emergency
treatment is required, for example, administration
of epinephrine in the case of bee or wasp stings. See
also 
allergic reaction.