What are allergies?
Allergies are problems of the body's immune system. Most allergic reactions happen when
the immune system reacts to a false alarm. Normally the immune system attacks harmful
things such as viruses or bacteria. But sometimes it overreacts and responds to things
that are normally harmless. These include dust, mold, pollen, or food.
What causes allergies?
Allergens are substances that can be breathed or swallowed, or that come in contact
with the skin. Common allergic reactions, such as hay fever, certain types of asthma,
and food allergies are linked to an antibody made by the body. This antibody is called
immunoglobulin E or IgE. Each IgE antibody targets a certain allergen. When IgE comes
into contact with its target allergen, it triggers the release of several inflammatory
chemicals. These include histamines, cytokines, and leukotrienes. These chemicals then
cause allergy symptoms.
You can be allergic to one type of
allergen, but not another. Allergic reaction symptoms will differ based on the type and
amount of allergen you have come in contact with. It also depends on how your body’s
immune system reacts to that allergen. Symptoms can range from mild itching or runny
nose to a severe allergic reaction (anaphylaxis).
most common allergens are:
- Household dust, dust mites and their waste
dander, urine, or oil from skin
- Chemicals used for manufacturing
- Cockroaches and their waste
Who is at risk for
Allergies can affect anyone, at any age. Often allergies are more common in children.
But a first-time event can happen at any age, or come back after many years of
Allergies often run in families. But the exact family links that cause allergies aren’t
yet understood. In sensitive people, things such as hormones, stress, smoke, perfume, or
other environmental irritants may also play a role. Allergy symptoms often grow slowly
may become used to constant symptoms such as sneezing, nasal congestion, or wheezing.
You may not think that the symptoms are abnormal. But these symptoms can often be
stopped or controlled with the help of a doctor who specializes in treating allergies
(allergist). And you can have a better quality of life.
What are allergy
allergic reaction can happen anywhere in the body. This includes the skin, eyes, stomach
lining, nose, sinuses, throat, and lungs. These are the places where immune system cells
are found to fight off germs that are breathed in, swallowed, or come in contact with
the skin. Allergic reactions can cause these symptoms:
nose, sneezing, itching, or runny nose, and itching in ears or roof of mouth
itchy, watery eyes
itchy, dry skin
- Hives or
symptoms, such as shortness of breath, coughing, wheezing
- Anaphylaxis, a severe, life-threatening reaction
The symptoms of allergy sometimes look like other conditions or health problems. Always
see your healthcare provider for a diagnosis.
How are allergies
diagnose an allergy, your healthcare provider will give you an exam and review your
health history. He or she may also do these tests:
- Skin test. This the most common allergy test. Skin
tests measure if there are IgE antibodies to specific allergens such as foods,
pollens, or animal dander. A small amount of diluted allergen is placed on the skin.
The area is pricked or scratched. If you are allergic to the allergen, a small raised
bump (like a mosquito bite) will appear after about 15 minutes. Testing for many
allergens may be done at the same time. An allergist may also do an intradermal test.
In this test, a small amount of allergen is injected just under the skin. This type
of skin testing is more sensitive than prick or scratch testing. Skin test results
are available right after the testing is done.
- Blood test. Blood tests for allergies measure IgE
antibodies to specific allergens in the blood. The test that is most often used is
called RAST (radioallergosorbent test). Or a newer blood test called an ELISA
(enzyme-linked immunosorbent assay) may be done. Blood tests may be used when skin
tests can't be done. For example, in people with particular skin conditions or a very
recent severe allergic reaction. A positive blood test does not always mean that you
have a specific allergy. These tests take longer and may be more expensive than skin
- Challenge test. Challenge
tests may be done when it is not clear what allergen is triggering your symptoms. It
is often done with possible medicine or food allergies. For the test, you may breathe
in a very small amount of allergen. Or you may take a very small amount of the
allergen by mouth. You will be watched closely by a healthcare provider during this
See your healthcare provider about any positive test result. He or
she can tell you about the tests and knows your health history.
How are allergies treated?
Treatment will depend on your symptoms, age, and general health. It
will also depend on how severe the condition is.
Allergy shots (immunotherapy) and medicine are effective ways treat allergies.
Allergy shots (immunotherapy)
Allergy shots (immunotherapy) are used to treat people who have hay fever (allergic
rhinitis), conjunctivitis, or asthma. They are also used for people with a stinging
insect allergy (bee venom allergy). A mixture of the many allergens to which you are
allergic is made. It is injected into your arm on a weekly basis until a maximum dose
is reached. Then the number of injections is decreased over time.
Most people get better with allergy shots. It often takes about 12 to 18 months
before you notice a clear reduction in symptoms. Some people see improvement in 6 to
Allergy shots are only part of the treatment plan for people with allergies. It
takes time for allergy shots to become effective. So you will need to stay on the
allergy medicines as prescribed by your healthcare provider. It is also important to
keep allergens (such as dust mites) under control in your surroundings.
newer type of immunotherapy is called SLIT (sublingual immunotherapy). It can be
taken by mouth daily at home. It is an effective alternative to allergy shots. But it
is currently only available for a few allergens.
For people who suffer from allergies, there are many medicines that work well. Nasal
sprays work to decrease nasal congestion, stuffiness, and post nasal drip.
Antihistamines are helpful for itchiness and hives. Decongestants are used to treat
stuffiness in the nose and other symptoms linked to colds and allergies. But overuse
of decongestants can be linked to rebound congestion or high blood pressure. Using
medicines for asthma or allergy breathing symptoms is tailored for each person based
on the severity of the symptoms.
Talk with your healthcare provider for more information about allergy medicines.
What are possible complications of
Anaphylactic shock or anaphylaxis can happen in extreme cases. Anaphylaxis is a
serious, life-threatening reaction to certain allergens. Body tissues may swell,
including tissues in the throat. It can also cause a sudden drop in blood pressure.
Anaphylaxis symptoms include:
and hives over most of the body
and tongue swelling
- Trouble breathing
cramps, nausea, or diarrhea
- Loss of
Anaphylaxis can be caused by an allergic reaction to a medicine, food, serum, bug
venom, allergen extract, or chemical. Pollen, pets, dust, and mold allergies are
unlikely to cause anaphylaxis. Some people who are aware of their allergic reactions or
allergens carry epinephrine autoinjectors. This medicine can be used to treat severe
allergic reaction. It can also prevent anaphylactic shock from foods, stinging insects,
and other allergens. It does this by improving circulation, contracting blood vessels,
and opening up the airways in the lungs. It also increases the rate and force of the
Living with allergies
Staying away from allergens is a very effective way to treat allergies. Tips for
avoiding allergens include:
indoors when the pollen count is high and on windy days.
dust in your home, particularly the bedroom.
- When possible, get rid of carpeting, blinds, down-filled blankets or pillows,
and closets filled with clothes.
- Wash bedding, curtains, and clothing often in hot water to get rid of dust
- Use dust mite covers over your mattress and pillow.
- Use air
conditioning instead of opening the windows.
- Put a
dehumidifier in damp parts of the home. But remember to clean it often.
face masks when working in the yard.
- Go on
vacation by the beach during the heaviest part of the pollen season.
Your healthcare provider will also have suggestions for staying away from the allergens
that cause reactions.
Key points about allergies
allergy is a reaction caused when the immune system mistakenly thinks a normally
harmless substance is harming the body.
- Allergens can be breathed, swallowed, or enter through the skin.
- Allergies can affect anyone at any age. They often run in families. But the exact
family links that cause allergies aren’t fully understood.
allergic reaction can occur anywhere in the body. Symptoms can include stuffy nose,
sneezing, watery eyes, hives, and itchy rash.
- Anaphylactic shock (anaphylaxis) can happen in extreme cases.
Anaphylaxis is a serious, life-threatening reaction to certain allergens.
most effective ways to treat allergies are staying away from allergens, getting
allergy shots (immunotherapy), and taking medicine.
to help you get the most from a visit to your healthcare provider:
the reason for your visit and what you want to happen.
your visit, write down questions you want answered.
someone with you to help you ask questions and remember what your provider tells
- At the
visit, write down the name of a new diagnosis, and any new medicines, treatments, or
tests. Also write down any new instructions your provider gives you.
why a new medicine or treatment is prescribed, and how it will help you. Also know
what the side effects are.
- Ask if
your condition can be treated in other ways.
why a test or procedure is recommended and what the results could mean.
what to expect if you do not take the medicine or have the test or procedure.
- If you
have a follow-up appointment, write down the date, time, and purpose for that
- Know how
you can contact your provider if you have questions.
Online Medical Reviewer:
Daphne Pierce-Smith RN MSN CCRC
Online Medical Reviewer:
Deborah Pedersen MD
Date Last Reviewed:
© 2000-2018 The StayWell Company, LLC. 800 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.