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).
The most common allergens are:
Household dust, dust mites and their waste
Animal dander, urine, or oil from skin
Chemicals used for manufacturing
Cockroaches and their waste
Who is at risk for allergies?
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 remission.
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 over time.
You 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 symptoms?
An 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:
Stuffy nose, sneezing, itching, or runny nose, and itching in ears or roof of mouth
Red, itchy, watery eyes
Red, itchy, dry skin
Hives or itchy welts
Asthma 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 diagnosed?
To 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 tests.
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
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 8 months.
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.
A 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
Talk with your healthcare provider for more information about allergy medicines.
What are possible complications of allergies?
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
Itching and hives over most of the body
Throat and tongue swelling
Stomach cramps, nausea, or diarrhea
Loss of consciousness
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
Stay indoors when the pollen count is high and on windy days.
Control 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 mites.
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.
Wear 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
An 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.
An 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.
The most effective ways to treat allergies are staying away from allergens, getting
allergy shots (immunotherapy), and taking medicine.
Tips to help you get the most from a visit to your healthcare provider:
Know the reason for your visit and what you want to happen.
Before your visit, write down questions you want answered.
Bring 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.
Know 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.
Know why a test or procedure is recommended and what the results could mean.
Know 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.