An allergy is an immune response or reaction to a substance that is usually not harmful. Normally, the immune system protects your body from harmful substances like bacteria and viruses. If you develop allergies, your body’s immune response is oversensitive to foreign substances called allergens. Genes and environment determine if you have allergies. If one of your parents has allergies, you have up to a 50 percent risk; if two parents have allergies, you have about an 80 percent risk of getting allergies.
Causes
Allergic reactions occur when the body recognizes an allergen and the immune system launches a response. Chemicals called histamines cause allergy symptoms. You can develop an allergy at any time, even to something that isn’t new in your life. Common allergens include dust, food, insect venom, mold, pet dander, drugs, and pollen.
Symptoms
Allergens you breathe in may cause allergic rhinitis: a stuffy or runny nose, itchy nose and throat, and itching of the roof of the mouth and/or ears. Allergic rhinitis may cause production of a fluid called mucus. This fluid is usually thin and clear but may thicken and become yellow or green as it dries or stays in your nose. The color of mucus doesn't mean you have an infection that needs antibiotics, it gets darker as it dries out. Mucus helps keep dust, debris, and allergens out of the lungs by trapping particles.
You may have eye symptoms from the allergic response in your nose or an allergen near your eye. This may cause allergic conjunctivitis, or inflammation of the eye. Symptoms of allergic conjunctivitis include itchy, watery eyes and swollen, itchy lids. If eye allergies become severe, optometrists at the Student Health Center’s eye clinic can help.
Many people have sinus problems, skin problems (eczema), and asthma related to their body’s allergic response.
Treatment
The best way to reduce symptoms is to avoid what causes your allergies. Many allergies can’t be avoided. You can use medicine to prevent or treat your allergy symptoms.
Antihistamines
Antihistamines are available by prescription or over the counter and may be in the form of a pill, eye drops, liquid, injection, or nasal spray. Zyrtec/cetirizine, Claritin/loratadine, Xyzal/levocetirizine, Allegra/fexofenadine, and Benadryl/diphenhydramine are a few types of antihistamine.
Corticosteroids
Corticosteroids are anti-inflammatory medications that are also available in many forms including creams for the skin, eye drops, lung inhaler, or nasal spray. A nasal spray like Flonase/fluticasone, Nasacort/triamcinolone or others can help prevent and control nose and eye allergy symptoms by stopping the reaction where it starts – in your nose.
Decongestants
Decongestants can help relieve a stuffy nose and may come in the form of a pill or nasal spray. Decongestant nasal sprays (Afrin/oxymetazoline) should not be used for more than a few days because they can cause a “rebound” effect and make congestion worse. People with high blood pressure, heart problems, or prostate enlargements should use decongestants with caution.
Allergy shots
Allergy shots can help when you cannot avoid the allergen or your symptoms are difficult to keep under control. Allergy shots involve regular doctor’s visits and injections of the allergen, and help to keep your body from overreacting to the allergen. Some prescription medicines called leukotriene inhibitors block the substances that trigger allergies, especially for people with asthma or indoor and outdoor allergies.
When to contact a medical professional
Anaphylaxis is a rare but life-threatening reaction to allergies. Call 911 if you have:
- Trouble breathing
- Tightness in throat and/or chest
- Hoarse voice
- Nausea
- Vomiting
- Dizziness
- Swelling of face/mouth/tongue
- Faintness or fainting
- Fast heart rate
- A feeling of a sense of doom
- Abdominal pain
- Diarrhea
You may need epinephrine. Identify and avoid your allergy triggers, carry epinephrine, and wear medical identification alert about your allergy.
Call your health care provider for an appointment if your allergy treatment is no longer working or you have new allergy symptoms.
Additional resources
For more information about allergies, visit:
Updated 6/2022