Allergy Overview

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 your immune system (your body’s defense system) to react. Substances that cause these reactions are called allergens.

What is an allergic reaction?

An “allergic reaction” is the way your body responds to the allergen. A chain of events occur that result in an allergic reaction.

If you are prone to allergies, the first time you’re exposed to a specific allergen (such as pollen), your body responds by producing allergic (IgE) antibodies. The job of these antibodies is to find the allergens and help remove them from your system. As a result, a chemical called histamine is released and causes symptoms of allergies.

What are the types of allergies and how are they treated?

You can be allergic to a wide variety of substances – including pollen, animal dander, mold and dust mites.

Pollen

Seasonal allergic rhinitis, or hay fever, is an allergic response to pollen. It causes inflammation and swelling of the lining of your nose and of the protective tissue of your eyes (conjunctiva).

Symptoms include sneezing, congestion (feeling stuffy), and itchy, watery eyes, nose and mouth. Treatment options include over-the-counter and prescription oral antihistamines, anti-leukotrienes, nasal steroids, nasal antihistamines, and nasal cromolyn. In some people, allergic asthma symptoms (wheezing, shortness of breath, coughing, and/ or chest tightness) can be caused by exposure to pollen.

Your symptoms can be reduced by avoiding pollen. Stay indoors when pollen counts are high, close your windows, and use air conditioning. Ask your healthcare provider about immunotherapy (“allergy shots”) to treat pollen allergy.

Dust mites

Dust mites are tiny organisms that live in dust and in the fibers of household objects, such as pillows, mattresses, carpet, and upholstery. Dust mites grow in 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 with a high-efficiency filter vacuum cleaner. Treatment may include medications to control your nasal/eye and chest symptoms. Immunotherapy may be recommended if your symptoms are not adequately controlled with avoidance methods and medications.

Molds

Molds are tiny fungi (like Penicillium) with spores that float in the air like pollen. Mold is a common trigger for allergies. Mold can be found indoors in damp areas, such as the basement, kitchen, or bathroom, as well as outdoors in grass, leaf piles, hay, mulch or under mushrooms. Mold spores reach a peak during hot, humid weather.

Treatment may include medications to control your nasal/eye and chest symptoms. Immunotherapy may be recommended if your symptoms are not adequately controlled with avoidance and medications.

Animal dander

Allergic reactions can be caused by the proteins secreted by sweat glands in an animal’s skin, which are shed in dander, and by the proteins in an animal’s saliva. Avoidance measures don’t work as well as simply removing the pet from your home. However, because many people are reluctant to do this, second-best measures include keeping your pet out of your bedroom, using air cleaners with HEPA filtration and washing your pet (cat or dog) frequently.

Treatment may include medications to control your nasal/eye and chest symptoms. Immunotherapy may be recommended if your symptoms are not adequately controlled with avoidance methods and medications.

Latex

Some people develop a latex allergy after repeated contact with latex. Rubber gloves, such as those used in surgery 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 if you have a latex allergy.

Allergic reactions to latex can be mild, such as skin redness and itching. More severe reactions can occur if your 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 and avoidance.

Certain foods

Food allergies develop when your body develops a specific antibody to a specific food. An allergic reaction occurs within minutes of eating the food, and symptoms can be severe. In adults, the most common food allergies are shellfish, peanuts and tree nuts. In children, they include milk, egg, soy, wheat, shellfish, peanuts and tree nuts.

If you have a food allergy, your symptoms include itching, hives, nausea, vomiting, diarrhea, breathing difficulties and swelling around your mouth.

It is extremely important to avoid the foods that cause allergy symptoms. If you (or your child) have a food allergy, your doctor may prescribe injectable epinephrine (adrenaline) for you to carry at all times. This is needed in case you accidentally eat foods that cause allergies. There are new therapies for peanut allergies called oral immunotherapy.

Insect venom (stings)

If you get a bee sting, a normal reaction includes pain, swelling and redness around the sting site. A large, local reaction includes swelling that extends beyond the sting site. For example, if you are stung on the ankle, you may see swelling in your leg.

The most serious reaction to an insect sting is an allergic one, which needs immediate medical attention. Symptoms of an allergic reaction to an insect sting include:

  • Difficulty breathing.
  • Generalized (widespread) hives that appear as a red, itchy rash that spreads to areas other than the area that was stung.
  • Swelling of your face, throat or mouth tissue.
  • Wheezing or difficulty swallowing.
  • Restlessness and anxiety.
  • Rapid pulse.
  • Dizziness or a sharp drop in your blood pressure.

If you have a reaction like this, a re-sting can cause a serious reaction that can be life-threatening.

An allergic reaction is treated with epinephrine (adrenaline). If you’ve had an allergic reaction to bee stings, see a board-certified allergy/immunologist to get a skin and/or blood test to confirm your allergy to bee venom. Venom immunotherapy is recommended if venom allergy is confirmed. This will help reduce the possibility that a 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 is nasal allergies that change with the seasons because of 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 your child develops an allergy, it is very likely that you or your partner has allergies.

How common are allergies?

More than 50 million Americans (1 in 6) experience all types of allergies, including indoor/outdoor allergies, food and drug, latex, insect, skin and eye allergies. The number of people who have allergies continues to increase across all ages, sex and racial groups.

Symptoms and Causes

What are the symptoms of allergies?

Allergy symptoms are classified as mild, moderate or severe:

  • Mild reactions include local symptoms (affecting a specific area of your 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 your body.
  • Moderate reactions include symptoms that spread to other parts of your body. Symptoms may include itchiness, hives, and/or swelling and trouble breathing.
  • A severe allergic reaction, known as anaphylaxis, is a rare, life-threatening emergency in which your body’s response to the allergen is sudden and affects the whole body. Anaphylaxis may begin with severe itching of your eyes or face. Within minutes, more serious symptoms appear, including throat swelling (which could cause problems with swallowing and breathing), abdominal pain, cramps, vomiting, diarrhea, hives and swelling (angioedema). You may also have mental confusion or dizziness, since anaphylaxis may cause a drop in blood pressure.

What causes allergies?

Anything that you come into contact with that your body views as a “harmful invader” can be a cause of an allergy. Normally harmless substances that are common causes of allergies include pollen, animal dander, mold, dust, foods, insect venom and latex

Technically, your symptoms are the result of a chain of events that are your body’s response to the “harmful invader.” Your body “sees” the invader, makes antibodies to fight the invader, and in so doing, releases histamines that cause your allergy symptoms.

Diagnosis and Tests

How are allergies diagnosed?

If you think you have allergies, don't wait to see if your symptoms go away. When your symptoms last longer than a week or two and tend to come back, 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 checking your skin’s reaction.

If a skin test can’t be performed, blood work may be obtained. This test is not as sensitive as a skin test. The test evaluates the number of antibodies produced by your immune system. Higher levels of certain antibodies suggest possible allergy to that allergen.

Management and Treatment

How are allergies treated?

Although avoiding the allergen is an important treatment approach, it usually doesn’t completely end the allergic reaction.

Medications such as antihistamines (e.g., Allegra®, Zyrtec®), decongestants (eg, Sudafed®, Contact®), or a combination of over-the-counter and prescription medications, are used to treat your allergy symptoms. Nasal sprays such as topical nasal steroids (e.g., Flonase®, Nasonex®), cromolyn sodium, and topical nasal antihistamines also can be used to treat allergy symptoms.

Asthma medications, which reduce allergy symptoms, include:

  • Inhaled bronchodilators.
  • Inhaled steroids.
  • Oral bronchodilators (theophylline).
  • Oral anti-leukotrienes (montelukast [Singulair®], zafirlukast [Accolate®] and zileuton [Zyflo®]).
  • Injected medications, such as omalizumab (Xolair®), dupilumab (Dupixent®), reslizumab (Cinqair®), benralizumab (Fasenra®), or Mepolizumab (Nucala®).

Immunotherapy (“allergy shot therapy”) or allergy oral immunotherapy is recommended if your symptoms aren’t 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 (e.g., Neilmed®) are sold over-the-counter 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 eight ounces of distilled or boiled water. This mixture rinses out allergens and decreases the amount of inflammation (edema) they cause.

Outlook / Prognosis

Can allergies be cured?

Allergies can’t be cured, but symptoms can be controlled using a combination of avoidance measures and medications, as well as allergen immunotherapy in properly selected cases.

Last reviewed by a Cleveland Clinic medical professional on 11/30/2020.

References

  • American Academy of Allergy Asthma & Immunology. Allergies Accessed 11/16/2020.
  • Asthma and Allergy Foundation of America. Allergy Facts and Figures Accessed 11/16/2020.

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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy