A common allergic reaction often affecting the face, elbows and knees
is atopic dermatitis, also known as eczema. This red, scaly, itchy rash
is usually seen in young infants, but can occur later in life in individuals
with personal or family histories of atopy, meaning asthma or allergic
rhinitis ("hay fever").
Allergic contact dermatitis is best exemplified by the itchy, red,
blistered reaction that almost everyone experiences after touching a
plant in the "rhus" family-poison ivy, poison oak or poison
sumac
Hives or urticaria are red, itchy, swollen areas of the skin that
can range in size and appear anywhere on the body
Most common are acute cases of hives, where the cause is identifiable-often
a viral infection, drug, food or latex
Angioedema, a swelling of the deeper layers of the skin, sometimes
occurs with hives. Angioedema is not red or itchy, and most often occurs
in soft tissue such as the eyelids, mouth or genitals
Hives and angioedema may appear together or separately on the body.
When some substances come into contact with skin, they may cause a
rash called contact dermatitis. Some of these reactions are the result
of an allergic reaction that involves the immune system, but many are
the result of a non-allergic, or irritant, reaction.
Statistics:
Allergic dermatitis (itchy rash) is the most common skin condition
in children younger than 11 years of age. The percentage of children
diagnosed with it has increased from 3% in the 1960s to 10% in the 1990s.
Acute urticaria (hives) is common, affecting 10 to 20 percent of the
population at some time in their lives. Half of those affected continue
to have symptoms for more than 6 months.
Contact dermatitis and other eczema was diagnosed at over 8.5 million
office visits to physicians and at 499,000 hospital outpatient visits.
Atopic dermatitis is one of the most common skin diseases, particularly
in infants and children. The estimated prevalence in the United States
is 9 percent. The prevalence of atopic dermatitis appears to be increasing.
New Research:
Advances in Allergic Skin Diseases, Anaphylaxis, and Hypersensitivity
Reactions to Foods, Drugs and Insect Stings (JACI July 2004; Scott Sicherer,
MD, FAAAAI, et. al)
The addition of Zafirlukast to Cetirizine improves the treatment of
chronic urticaria to autologous serum skin test positive patients (JACI
Jan. 2004; Bagenstose et. al)