Allergies are an overreaction of the
body's natural defense system that helps fight infections (immune system). The immune system normally protects
the body from viruses and bacteria by producing
antibodies to fight them. In an
allergic reaction, the immune system starts fighting
substances that are usually harmless (such as
dust mites, pollen, or a medicine) as though these
substances were trying to attack the body. This overreaction can cause a rash,
itchy eyes, a runny nose, difficulty breathing, nausea, and diarrhea.
An allergic reaction may not occur the first time you are exposed to an
allergy-producing substance (allergen). For example, the first time
you are stung by a bee, you may have only pain and redness from the sting. If
you are stung again, you may have
hives or difficulty breathing. This is caused by the
response of the immune system.
Most people will have some problem
with allergies or allergic reactions at some point in their lives. Allergic
reactions can range from mild and annoying to sudden and life-threatening. Most
allergic reactions are mild, and home treatment can relieve many of the
symptoms. An allergic reaction is more serious when severe allergic reaction
(anaphylaxis) occurs, when
allergies cause other problems (such as nosebleeds,
ear problems, wheezing, or coughing), or when home treatment does not
help.
There are many types of
allergies. Some of the more common ones include:
Food allergies, which are more common in children than
adults. Food allergies are most common in people who have an inherited tendency
to develop allergic conditions. These people are more likely to have asthma and
other allergies. For more information, see the topic
Food Allergies.
Medicine allergies. Many prescription
and nonprescription medicines can cause an allergic reaction. Allergic
reactions are common and unpredictable. The seriousness of the allergic
reaction caused by a certain medicine will vary.
Allergies to insect venom. When you are stung by an
insect, poisons and other toxins in the insect's venom enter your skin. It is
normal to have some swelling, redness, pain, and itching at the site of a
sting. An allergic reaction to the sting occurs when your body's immune system
overreacts to the venom of stinging insects. For more information, see the
topic Allergies to Insect Stings.
Allergies to animals, which are more likely to cause breathing problems than skin
problems. You may be allergic to your pet's dead skin (dander), urine, dried
saliva, or hair.
Allergies that develop from exposure to a
particular inhaled substance in the workplace. These are called
occupational asthma.
Allergies to
cosmetics, such as artificial nails, hair extensions, and henna tattoos.
Seasonal allergies show up at the same
time of the year every year and are caused by exposure to pollens from trees,
grasses, or weeds. Hay fever is the most common seasonal allergy.
Allergies that occur for more than 9 months out of the year are called
perennial allergies. Between 20 and 40 million people in the United States are
affected by perennial allergies.
Year-round symptoms (chronic
allergies) are most likely to occur from exposure to
animal dander, house dust, or
mold.
Review the Emergencies and Check
Your Symptoms sections to determine if and when you need to see a
doctor.
Health Tools
Health Tools help you make wise health decisions or take action to improve your health.
Decision Points focus on key medical care decisions that are important to many health problems.
Swelling of the throat or tongue that causes difficulty
breathing
You had a severe reaction (anaphylaxis) in
the past from the same type of sting, bite, food, or medicine (allergen), and similar symptoms are developing.
Note:
Use an
allergy kit prescribed by your doctor for your allergy
problem if you have:
Severe symptoms.
A kit immediately
available, and you have been taught how and when to use it.
Had a
severe reaction in the past from the same type of sting, bite, food, or
medicine (allergen), and similar symptoms are developing.
Check Your Symptoms
If you answer yes to any of the following questions, click on the "Yes" in front of the question for information about how soon to see a health professional.
Review
health risks that may increase the seriousness of your
symptoms.
Review
health risks that may increase the seriousness of your
symptoms.
Call your health professional immediately if you answer "Yes" to
any of the following questions.
Note:
If you have used an epinephrine shot to treat an
allergic reaction or if you have been accidentally stuck with an epinephrine
shot and you are not able to contact your doctor:
Go immediately to the nearest hospital emergency room
for evaluation.
Take the used epinephrine shot with you. Your
doctor will want to inspect it and dispose of it properly.
Do you think your
symptoms may be caused by a
medicine?
Note:
If your answer is "Yes":
Call the doctor who prescribed the
medicine the same day (before your next dose) to determine whether you should
stop taking the medicine or take a different one. An appointment may not be
necessary.
If you are taking a nonprescription medicine, stop
taking it. If you feel you need to continue taking the medicine, call your
doctor.
If you have answered "No" to the above questions, go back to Check Your Symptoms and continue to answer the questions to evaluate your symptoms.
Swelling of the throat or tongue that causes difficulty
breathing
You had a severe reaction (anaphylaxis) in
the past from the same type of sting, bite, food, or medicine (allergen), and similar symptoms are developing.
Note:
Use an
allergy kit prescribed by your doctor for your allergy
problem if you have:
Severe symptoms.
A kit immediately
available, and you have been taught how and when to use it.
Had a
severe reaction in the past from the same type of sting, bite, food, or
medicine (allergen), and similar symptoms are developing.
Check Your Symptoms
If you answer yes to any of the following questions, click on the "Yes" in front of the question for information about how soon to see a health professional.
Review
health risks that may increase the seriousness of your
symptoms.
Review
health risks that may increase the seriousness of your
symptoms.
Call your health professional immediately if you answer "Yes" to
any of the following questions.
Note:
If you have used an epinephrine shot to treat an
allergic reaction or if you have been accidentally stuck with an epinephrine
shot and you are not able to contact your doctor:
Go immediately to the nearest hospital emergency room
for evaluation.
Take the used epinephrine shot with you. Your
doctor will want to inspect it and dispose of it properly.
Do you think your
symptoms may be caused by a
medicine?
Note:
If your answer is "Yes":
Call the doctor who prescribed the
medicine the same day (before your next dose) to determine whether you should
stop taking the medicine or take a different one. An appointment may not be
necessary.
If you are taking a nonprescription medicine, stop
taking it. If you feel you need to continue taking the medicine, call your
doctor.
If you have answered "No" to the above questions, go back to Check Your Symptoms and continue to answer the questions to evaluate your symptoms.
Hay fever symptoms. Take an
antihistamine to reduce symptoms of itchy, watery
eyes; sneezing; or a runny, itchy nose. Be sure to read and follow any warnings
on the label. Don't give antihistamines to your child unless you've checked
with the doctor first.
Allergies that are worse in damp weather. Mold may be the cause of allergies that get worse in damp
weather. Mold produces spores that move, like pollen, in outdoor air during
warmer months. During winter months, indoor molds can also be a
problem.
Indoor allergies. Newer, energy-saving homes that are
built with double- or triple-paned windows and more insulation keep heat as
well as allergens indoors.
Allergies to a pet or other animal. When allergies are worse around pets, symptoms may be caused by
your pet's dead skin (dander), urine, dried saliva, or hair.
Symptoms have not
improved after 1 to 2 weeks of home treatment.
Symptoms become more
severe or more frequent.
Prevention
To prevent problems with severe allergic
reactions:
If you or your child have had a severe allergic
reaction, talk to your doctor about getting a prescription for an
allergy kit. Learn when and how to use it, and have it
near you at all times. For more information, see:
If you have had an allergic reaction, wear a
medical identification tag to alert others to your allergies.
If
you know you have an allergy to a medicine, be sure any new doctor knows about
your allergy before prescribing a medicine for you.
If you have had
a severe allergic reaction to an insect bite or sting,
avoid the insect that caused the reaction. Allergy
shots may help reduce the severity of your reactions to insects. For more
information, see:
To prevent seasonal or year-round allergy reactions:
Control exposure to outdoor allergens. Limit
the time you spend outside during allergy season. This may be the best approach
to controlling your symptoms. If you have a seasonal allergy:
During the peak of the pollen or mold season, consider taking
your vacation in a place that has fewer of these
substances.
Exercise regularly. Exercise produces adrenaline, a
natural way to relieve a stuffy nose. However, exercising outdoors may also
expose you to more pollen or mold spores.
Control exposure to indoor allergens. Newer,
energy-saving homes built with double- or triple-paned windows and more
insulation keep
allergens as well as heat indoors.
Use an air conditioner or air purifier with a high-efficiency
particulate air (HEPA) filter.
Keep the house aired out and dry.
Keep the moisture level below 50%. Use a dehumidifier during humid
weather.
Dust and vacuum 1 to 2 times a week. Use a vacuum cleaner
with a HEPA filter, which collects dust-mite particles and pollen. Standard
paper bag filters may allow the stirred-up allergens to escape back into the
room.
Avoid carpet, upholstered furniture, and heavy drapes that
collect dust. Vacuuming doesn't pick up dust mites. Remove rugs and
wall-to-wall carpeting. Talk with your family about this measure and how this
will affect family life. Replace drapes and blinds with roll-down shades or
washable curtains.
Damp mop the floor once a day. Vacuum the walls,
ceiling, closet, and the backs of the furniture once a week to get rid of as
much dust as you can.
Use baking soda, mineral oil, club soda, or
vinegar to clean instead of harsher cleaning solutions that can produce
allergic reactions.
Contact a pest control service, if necessary,
to get rid of cockroaches. Cockroaches and dead insects may provoke allergic
responses if you have allergic asthma.
Avoid tobacco smoke, smoke
from wood-burning stoves, and fumes from kerosene heaters.
Keep air
registers closed if there is a pet in the house. This will reduce the amount of
animal dander circulating in the house, especially in
the bedroom.
Repair any water-damaged areas from leaking roofs or
basements. These areas can be prime mold-growing areas.
Control exposure to animal dander. Dander,
urine, and dried saliva (especially from cats, but also from small animals such
as mice and gerbils) are common allergens that can be spread throughout your
home by indoor pets. Hair is often not the problem. If your allergies are
severe, you may want to consider finding another home for your pet. Other
alternatives include the following:
Keep your pet out of your
bedroom.
Bath your pet once a week.
Ask a family member
who does not have allergies to clean your pet's litter box.
Keep a
caged pet, such as a gerbil, outside your home in a garage or shed.
Be sure to tell your child's school staff about
his or her allergies. This is important so the school knows how to help your
child if he or she has an allergic reaction.
Breast-feeding may prevent allergies. Breast-feed your baby
for at least 6 months if possible to boost his or her immune system. Feeding
only breast milk during the first 6 months of life may reduce the chances your
child will develop
food allergies or decrease the severity of your
child's allergies. For more information, see the topic
Breast-Feeding.
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