A guide to understanding allergies

Get to know the cause of allergies, the symptoms to look out for and the allergy treatment options that exist.

You know the drill: Your eyes itch. You can’t stop sneezing and your nose won’t stop running. It’s got to be allergies, you say to yourself — but do you really understand the root cause of those allergies? And do you know what to do about them?

“What we call allergies are actually an overreaction of the body’s immune system,” said Dr. Basil Kahwash, an immunologist with Vanderbilt Allergy, Sinus and Asthma Program. “Most allergic reactions happen when the immune system puts out a false alarm, reacting to a usually harmless substance as though it were harmful, like a virus or bacteria.”

The particles your immune system might react to commonly include pollen, dust and mold, as well as certain foods and medicines. These allergens can be breathed in or swallowed, or can enter through the skin. Common allergic reactions, such as hay fever, certain types of asthma and food allergies, are associated with an antibody made by the body. This type of 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,” Kahwash explained. “These include histamine, cytokines and leukotrienes. It’s these chemicals that then cause allergy symptoms, like watery eyes, a runny nose, sneezing, rashes — or in extreme cases, anaphylaxis.”

What are the most common allergens?

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. Here are a few common allergy types:

• Pollen
• Mold
• Household dust, dust mites and their waste
• Animal dander, urine or oil from skin
• Chemicals used for manufacturing
• Certain foods
• Certain medicines
• Feathers
• Bee stings
• Cockroaches and their waste
• Latex

What are allergy symptoms?

“An allergic reaction can happen just about anywhere in the body,” Kahwash said, “including the skin, eyes, stomach lining, nose, sinuses, throat and lungs, as these are the places where immune system cells fight off germs.” These allergic reactions include:

• 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 or wheezing
• Anaphylaxis, a severe, life-threatening reaction

Confusingly, the symptoms of an allergy sometimes look like other conditions or health problems. Always see your healthcare provider for a diagnosis, which can be made through allergy testing.

Medications for allergy treatment

“Medications are often the first line of defense against allergies,” Kahwash said, “and there are many medicines that work well.” Nasal sprays work to decrease nasal congestion, stuffiness and post-nasal drip. Antihistamines, like Benadryl, are helpful for itchiness and hives. Decongestants are also used to treat stuffiness in the nose and other symptoms, but overuse can lead to rebound congestion and high blood pressure. Your provider will work with you to tailor medicine use to your symptoms and their severity. Some medications are over-the-counter while others may require a prescription.

Treating allergies with shots (immunotherapy)

“Another tool we have in our toolbox is immunotherapy, which can be particularly effective for pollen or pet allergies,” Kahwash said. A mixture of the many allergens you test positive to is made and is injected into your arm on a weekly basis until a maximum dose is reached, and then the frequency of shots is decreased over time. “It often takes 12 to 18 months to see an improvement in symptoms, though some patients see improvement in as little as six months,” Kahwash said. “But the benefit is that it’s long-lasting and allows patients to be less dependent on medication.”

A newer type of immunotherapy is called SLIT (sublingual immunotherapy). It can be taken by mouth daily at home and is an effective alternative to allergy shots. However, it is currently only available for a few allergens.