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Allergy Overview

Allergies: What You Need to Know

  • An allergy is a reaction caused when the immune system mistakenly thinks a normally harmless substance is damaging to the body.

  • Allergens can be breathed or swallowed, or they can enter through the skin.

  • Allergies can affect anyone, no matter their age, gender, race or socioeconomic status.

  • To diagnose an allergy, your health care provider will give you an exam, take your medical health record and do blood and skin tests.

  • The three most effective ways to treat allergies are avoidance, allergy shots and medicine.

What are allergies?

Allergies are problems of the immune system. Most allergic reactions happen when the immune system reacts to a “false alarm.” Normally, the human body defends itself against harmful things, such as viruses or bacteria. But sometimes the defenses violently attack mostly mild things, such as dust, mold, or pollen.

The immune system makes large amounts of the antibodies called immunoglobin E (IgE). This is a complex chemical weapon that attacks and kills the “enemy.” Each IgE antibody exactly targets a certain allergen or thing that causes the allergy. In this way, inflammatory chemicals, such as histamines, cytokines, and leukotrienes, are made and given off. This causes an allergic person to feel some bad or even life-threatening symptoms.

What causes allergies?

Allergens are substances that can be breathed, swallowed, or come in contact with the skin. Common allergic reactions, such as hay fever, certain types of asthma, and hives, are linked to an antibody made by the body. This antibody is called immunoglobulin E or IgE. You can be allergic to one type of pollen, but not another. When you are exposed to an allergen, your body starts making a large amount of matching IgE antibodies. When exposed to the same allergen at a later point, you may have a reaction. Symptoms of an allergic reaction will differ based on the type and amount of allergen you have come in contact with. It also depends on how the body’s immune system reacts to that allergen.

The most common allergens are:

  • Pollen

  • Mold

  • Household dust, dust mites and their waste

  • Animal dander, urine, or oil from skin

  • Chemicals used for manufacturing

  • Food

  • Medicine

  • Feathers

  • Bug stings

  • Cockroaches and their waste

  • Latex

Who is at risk for allergies?

Allergies can affect anyone, no matter what age, gender, race, or socioeconomic status. 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.

There’s a tendency for allergies to happen in families. Although the exact family links that cause it aren’t yet understood. In sensitive people, things such as hormones, stress, smoke, perfume, or other environmental irritants, may also play a role. Often, the symptoms of allergies grow slowly over a period of time.

You may become used to constant symptoms, such as sneezing, nasal congestion, or wheezing. You may not think that the symptoms are unusual. But, these symptoms can often be stopped or controlled with the help of a doctor who specializes in treating allergies. And you can have a better quality of life.

What are the symptoms of allergies?

An allergic reaction can happen anywhere in the body. This includes the skin, eyes, lining of the stomach, nose, sinuses, throat, and lungs. These are the places where immune system cells are found to fight off germs that are in breathed in, swallowed, or come in contact with the skin. Allergic reactions can cause:

  • 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

  • Itchy rash

  • Asthma symptoms, such as shortness of breath, coughing, wheezing

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. The skin test is a way of measuring the level of IgE antibodies to certain allergens. Using diluted solutions of certain allergens, the healthcare provider either gives you a shot with the solutions or puts them directly on your skin by making a scratch or small puncture. A small red area on the skin means that you have had a reaction.

  • Blood test. The blood test is used to measure the level of IgE antibodies to specific allergens. One common blood test is called radioallergosorbent test or RAST. Newer tests have been developed that may be better than RAST. Ask your doctor about all available allergy blood tests.

More Information about Sinusitis from Johns Hopkins Medicine

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Dan’s Story: Sinus Surgery and Sublingual Therapy

Desperate after numerous unsuccessful sinus surgeries to treat an aggressive nasal infection, Virginia-resident Dan found the Johns Hopkins Sinus Center. After sinus surgery by Dr. Andrew Lane and sublingual immunotherapy allergy treatment by Dr. Sandra Lin, Dan is now infection free and no longer taking decongestants.

Read more.

How are allergies treated?

Your healthcare provider will figure out the best treatment for you based on:

  • Your age

  • Your overall health and medical history

  • How sick you are

  • How well you can handle specific medications, procedures, or therapies

  • How long the condition is expected to last

  • Your opinion or preference

The symptoms of allergy sometimes look like other conditions or medical problems. Always see your healthcare provider for a diagnosis.

Allergy shots or immunotherapy and medicine are effective ways treat allergies.

Allergy shots

Allergy shots or immunotherapy is treatment for people who have rhinitis (hay fever), conjunctivitis, or asthma. It is also used for people with a stinging bug 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.

Most people get better with allergy shots. It often takes from 12 to 18 months before you notice a clear reduction in allergy symptoms. In some people, a reduction in symptoms is evident in as soon as 6 to 8 months.

Allergy shots are only part of the treatment plan for people with allergies. Since it takes time for allergy shots to become effective, you will need to stay on the allergy meds, as prescribed by your healthcare provider. It is also important to keep getting rid of allergens (such as dust mites) from your surroundings.

Medicine

For people who suffer from allergies, there are many medicines that work well. Antihistamines are used to calm or stop the symptoms of allergic rhinitis (hay fever) and other allergies. Decongestants are used to treat stuffiness in the nose and other symptoms linked to colds and allergies. The use of medicines for asthma or breathing symptoms from allergies is tailored for each person based on the severity of the symptoms.

Talk with your healthcare provider for more information about allergy medicines.

More Information About Environmental Allergy Treatment from Johns Hopkins Medicine

Woman sneezing

Could allergy drops be the key to allergy relief?

Rather than suffer through allergy season, many people are choosing to fight back using immunotherapy, a treatment that works to boost your immune system and change the way your body responds to allergens. This treatment involves gradually introducing small amounts of what you’re allergic to.

Learn more.

What are the 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. These are the most common symptoms of anaphylaxis:

Other symptoms may include:

  • Itching and hives over most of the body

  • Swelling of the throat and tongue

  • Difficulty breathing

  • Dizziness

  • Headache

  • Stomach cramps, nausea, or diarrhea

  • Shock

  • Loss of consciousness

Anaphylaxis can be caused by an allergic reaction to a drug, food, serum, bug venom, allergen extract, or chemical. Some people who are aware of their allergic reactions or allergens carry epinephrine. This drug can counteract many of the complications of anaphylaxis, as it can cause the circulation to improve by helping the dilated blood vessels constrict and open up the airways in the lungs. It also increases the rate and force of the heartbeat.

Living with allergies

Avoidance is a very effective way to treat allergies. Ideas for avoiding allergens are:

  • Stay indoors when the pollen count is high and on windy days.

  • Dust-proof your home, particularly the bedroom.

    • When possible, get rid of carpeting, Venetian blinds, down-filled blankets or pillows, closets filled with clothes.

    • Wash bedding, curtains, and clothing often in hot water to get rid of dust mites.

    • Keep bedding in dust covers when possible.

  • 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 avoiding 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 damaging to the body.

  • Allergens can be breathed, swallowed, or enter through the skin.

  • Allergies can affect anyone, no matter what age, gender, race, or socioeconomic status.

  • Allergies tend to happen in families. Although the exact family links that cause it aren’t yet understood.

  • Allergic reactions may cause:

    • 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

    • Itchy rash

    • Asthma problems, such as shortness of breath, coughing, and wheezing

  • The most effective ways to treat allergies are avoidance, allergy shots, and medicine.

  • Anaphylaxis can happen in extreme cases.

For information about food allergies please visit the following pages:

More Information About Environmental Allergies in the Health Library

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