Allergy Overview
What are allergies?
Allergies are your body’s reaction to a substance it
views as a harmful ‘invader.’ For example, coming into contact with what is
normally a harmless substance, such as pollen, might cause the immune system
(the body’s defense system) to react. Substances that cause these reactions are
called allergens.
What is an allergic reaction?
An "allergic reaction" is way the body responds to the
allergen. A chain of events occur that result in an allergic reaction, described here.
The first time an allergy-prone person is exposed to a
specific allergen (such as pollen), the body responds by producing allergic
(IgE) antibodies. The job of these antibodies is to find molecules of the
offending substance in the bloodstream and tissues and to escort them to the
body’s mast cells (a type of white blood cell) for destruction. As the mast
cells destroy the allergens, a chemical called histamine is released into the
bloodstream. A large amount of histamine swells body tissues (inflammation),
causes itching, enlarges blood vessels, increases secretions, and causes
bronchospasm (tightening of muscles that surround the airways).
What are the symptoms of allergies?
Allergy symptoms can be classified as mild, moderate, or severe.
- Mild reactions include local symptoms (affecting a specific
area of the body) such as a rash or hives; itchiness, watery/red eyes, hay
fever, and runny nose. Mild reactions do not spread to other parts of the body.
- Moderate reactions include symptoms that spread to other parts
of the body. Symptoms may include itchiness, hives, and/or swelling, and
breathing difficulties.
- A severe allergic reaction, known as anaphylaxis, is a
rare, life-threatening emergency in which the body’s response to the
allergen is sudden and affects the whole body. Anaphylaxis may begin with
severe itching of the eyes or face. Within minutes, more serious symptoms
appear, including throat swelling (which could result in difficulty
swallowing and breathing); abdominal pain; cramps; vomiting; diarrhea;
hives; and swelling (angioedema). Mental confusion or dizziness may also
result, since anaphylaxis may cause a drop in blood pressure.
What are the types of allergies and how are they treated?
People can be allergic to a wide variety of
substances, the most common of which are pollen and dust mites. Other airborne
allergens include molds and animal dander.
Pollen
Seasonal allergic rhinitis, or hay fever, is an
allergic response to pollen. It causes inflammation and swelling of the lining
of the nose and of the protective tissue of the eyes (conjunctiva).
Symptoms include sneezing, congestion, and itchy,
watery eyes. Treatment options include over-the-counter and prescription
antihistamines, anti-leukotrienes, nasal steroids, and nasal cromolyn. Some
individuals may have allergic asthma symptoms (wheezing, shortness of breath,
chest tightness) provoked by exposure to pollen. Symptoms can be reduced by
avoiding pollen. Stay indoors when pollen counts are high, close windows, and
use air conditioning. Immunotherapy (‘allergy shots’) also may be used to treat
pollen allergy.
Dust mites
Dust mites are microscopic organisms that live in dust
and in the fibers of household objects, such as pillows, mattresses, carpet, and
upholstery. Dust mites especially love warm, humid areas.
The symptoms of dust mite allergy are similar to those
of pollen allergy. To help manage dust mite allergies, try using dust mite
encasements (airtight plastic/polyurethane covers) over pillows, mattresses, and
box springs. Also, remove carpet, or vacuum frequently, using a vacuum cleaner
with high-efficiency filters. Treatment may include medications to control
nasal/eye and chest symptoms. Immunotherapy may be recommended for people whose
symptoms are not adequately controlled with avoidance methods and medications.
Molds
Molds are parasitic, microscopic fungi (like Penicillium) with spores that float
in the air like pollen. Mold is a common trigger for allergies and can be found indoors in
damp areas, such as the basement or bathroom, as well as in the outdoor environment in grass, leaf
piles, hay, mulch, or under mushrooms. Mold spores peak during hot, humid weather.
Treatment may include medications to control nasal/eye
and chest symptoms. Immunotherapy may be recommended for people whose symptoms
are not adequately controlled with avoidance and medications.
Animal dander
The proteins secreted by sweat glands in an animal’s
skin, which are shed in dander, and to a lesser extent the proteins present in
an animal’s saliva, can cause allergic reactions in some people. No avoidance
measures can compare with removing the pet from the home. However, because many
people are reluctant to do this, second-best measures include restricting the
pet from the bedroom, using air cleaners with HEPA filtration, and washing the
pet (cat or dog) frequently.
Treatment may include medications to control nasal/eye
and chest symptoms. Immunotherapy may be recommended for people whose symptoms
are not adequately controlled with avoidance methods and medications.
Other allergens include:
Latex
A latex allergy may develop in some individuals after
repeated contact with latex. Rubber gloves, such as those used in surgical
procedures or home cleaning, are a major source for causing this type of
reaction. Skin rash, hives, eye tearing and irritation, wheezing, and itching of
the skin may occur in persons with latex allergy. Allergic reactions to latex
can be mild, such as skin redness and itching. More severe reactions can occur
if the mucosal membranes are exposed, such as during an operation or a dental or
gynecologic exam.
Treatment of latex reactions begins by removing the
offending latex product. If you have latex allergy, it is important for you to
wear a Medic Alert bracelet and carry an emergency epinephrine kit. All
procedures should be carried out in a "latex safe" fashion. There is no cure for
latex allergy, so the best treatment for this condition is prevention.
Certain foods
Food allergies develop when the body develops a
specific antibody to a specific food. An allergic reaction occurs within minutes
of eating the food, and symptoms can be severe. Shellfish, peanuts, and tree
nuts are the most common food allergies in adults. Milk, egg, soy, wheat,
shellfish, peanuts, and tree nuts are the most common food allergies in children.
Symptoms of food allergy include itching, hives,
nausea, vomiting, diarrhea, breathing difficulties, and swelling in the area
around the mouth.
The only treatment is to avoid the foods that cause
allergy symptoms. If you (or your child) have food allergy, your doctor may
prescribe injectable epinephrine (adrenaline) for you to carry at all times.
This is necessary in case foods that cause allergies are accidently eaten.
Insect venom (stings)
If stung by a bee, the bee usually injects a sac of
venom and may leave a stinger in the victim's skin. If the stinger is still in
the skin, gently scrape it out with a fingernail or a stiff-edged object like a
credit card. Do not pull on the stinger, as this will cause the release of more
venom into the skin.
A normal reaction will result in pain, swelling, and
redness around the sting site. A large, local reaction may occur that will
result in swelling that extends beyond the sting site. For example, a person
stung on the ankle may have swelling of the leg. The most serious reaction to an
insect sting is an allergic one, requiring immediate medical attention. Symptoms
of an allergic reaction to an insect sting include difficulty breathing;
generalized hives that appear as a red, itchy rash that spreads to areas other
than the immediate area stung; swelling of the face, throat, or mouth tissue;
wheezing or difficulty swallowing; restlessness and anxiety; rapid pulse; and
dizziness or a sharp drop in blood pressure. If such a reaction has occurred, a
re-sting has the potential to cause a serious reaction that can be
life-threatening.
An allergic reaction is treated with epinephrine
(adrenaline), either self-injected or administered by a doctor. Those who have
had allergic reactions from bee stings should be seen by a board-certified
allergy/immunology physician to confirm allergic potential by skin and/or blood
testing to bee venom. Venom immunotherapy is recommended when venom allergy is
confirmed. This will help reduce the possibility that re-sting will cause a
serious reaction.
What is allergic rhinitis?
Nasal allergy symptoms and hay fever are referred to
as "allergic rhinitis." Seasonal allergic rhinitis describes nasal allergies
that change with the seasons due to pollen from plants (trees, grasses, or
weeds). Seasonal symptoms arise during the pollinating seasons for particular
plants. Because you can be allergic to more than one thing, your symptoms may
get worse at different times throughout the year or may be constant.
Does everyone get allergies?
No. Most allergies are inherited, which means they are
passed on to children by their parents. People inherit a tendency to be
allergic, although not to any specific allergen. If a child develops an allergy,
it is very likely that at least one of his or her parents has allergies.
How common are allergies?
More than 50 million Americans suffer from all types
of allergies (1 in 6), including indoor/outdoor allergies, food and drug, latex,
insect, skin and eye allergies. Allergy prevalence continues to increase across
all ages, sex, and racial groups.
How are allergies diagnosed?
If you think you have allergies, don’t wait to see if
your symptoms will go away. When your symptoms last longer than a week or two
and tend to recur, make an appointment with an allergy/immunology specialist.
Allergy skin testing may be used to identify the
allergens that are causing your allergy symptoms. The test is performed by
pricking your skin with an extract of an allergen, and then evaluating the
skin’s reaction.
If a skin test cannot be performed, a
radioallergosorbent blood test (RAST) may be taken. This test is not as
sensitive as a skin test. This RAST evaluates the number of antibodies produced
by the immune system. Elevated levels of certain antibodies can identify
particular allergies.
How are allergies treated?
Although avoiding the allergen is an important treatment approach, it
usually does not completely resolve the allergic reaction.
Medications such as antihistamines (eg, Allegra®,
Zyrtec®), decongestants (eg, Sudafed®, Contact®),
or a combination of over-the-counter and prescription medications are used to
treat allergy symptoms.
Nasal sprays such as topical nasal steroids (eg, Flonase®, Nasonex®)
and cromolyn sodium also can be used to treat allergy symptoms.
Asthma medications, which reduce allergy symptoms
include inhaled steroids, inhaled and oral bronchodilators (theophylline), oral
anti-leukotrienes (zafirlukast [Accolate®] and zyflo [Zileuton®]),
and injected medications including an antibody such as omalizumab (Xolair®).
Immunotherapy, or "allergy shot therapy," is
recommended for symptoms not adequately controlled with a combination of
avoidance measures and regular medication use. This shot has been shown to be
effective in properly selected patients with allergic rhinitis and/or allergic asthma.
Another treatment option is saline irrigation using a
sinus rinse kit. These rinse kits are sold over-the-counter (eg, Neilmed) or can
be made at home. To make your own rinse, combine one-half teaspoon non-iodinated
salt with one-half teaspoon baking soda in 8 ounces of distilled or boiled
water. This mixture rinses out allergens and decreases the amount of
inflammation (edema) they cause.
Can allergies be cured?
Allergies cannot be cured, but symptoms can be
controlled using a combination of avoidance measures and medications, as well as
allergen immunotherapy in properly selected cases.
References
- American Academy of Allergy Asthma & Immunmology. Allergies.
www.aaaai.org/ Accessed 1/2/12
- Asthma and Allergy Foundation of America. Allergy Facts and Figures.
www.aafa.org/ Accessed 1/2/12
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