What Is an Allergy?
What Happens During an Allergic Reaction?
It starts when you come into contact with a trigger that you inhale, swallow, or get on your skin.
In response, your body starts to make a protein called IgE, which grabs onto the allergen. Then histamine and other chemicals get released into the blood. That causes the symptoms you notice.
What Are the Symptoms?
Your symptoms depend on how you’re exposed — through the air, your skin, food, or through an insect sting.
If you’ve got a nasal allergy (one that’s triggered by something you inhale), common symptoms include:
- Itchy, watery eyes
- Sneezing
- Itchy, runny nose
- Feeling tired or ill
Common symptoms of a skin allergy include rashes and hives (a rash with raised red patches). Your skin may be red, itchy, or swollen.
Symptoms can range from mild to severe. Most go away shortly after the exposure stops.
Mild ones may be almost unnoticeable. You might just feel a little “off.”
Moderate symptoms can make you feel ill, as if you’ve got a cold or even the flu.
Severe allergic reactions are extreme.
Is It Anaphylaxis?
The most severe allergic reaction is called anaphylaxis. It affects your whole body. Symptoms can include:
- Hives and itching all over
- Wheezing or shortness of breath
- Hoarseness or tightness in the throat
- Swelling of the face, eyelids, lips, tongue, or throat
- Tingling in the hands, feet, lips, or scalp
Anaphylaxis is life-threatening, so call 911 right away. If you have an epinephrine auto-injector, use it and repeat after 5 to 15 minutes if your symptoms haven’t improved. You’ll still need medical care right after you give yourself the shots, even if your symptoms seem to stop, because a delayed reaction could still happen.
Will your allergy symptoms get better or even go away? Or are they “chronic,” which means they are here for the long run?
The answer isn’t always simple. Each person’s case is different.
But as an adult, once you have an allergy, it usually doesn’t go away on its own.
When They Get Worse
Some people find that their allergies worsen over time. That’s especially true of allergies to foods, latex, or bee stings, which can result in more serious reactions with each exposure.
Other things also make a big difference. All it takes is a heavy pollen season, or a new job in a moldy building, for allergies to flare up.
Will You Get More Allergies?
If your allergy symptoms seem worse, there could be another reason. You might now have a second allergy — or third or fourth.
Allergies can interact in unexpected ways. For instance, up to a third of people who are allergic to pollens also have allergies to foods that have similar proteins in them, like certain vegetables and fruits. Doctors call this “oral allergy syndrome. You could have more severe allergic reactions if you’re exposed to both at once — for instance, if you eat a banana at the height of ragweed allergy season.
The key is to manage your symptoms and let your doctor know if you notice changes.
Why Allergies Happen
You might blame your triggers — the pollen in the air, your best friend’s cat — for your symptoms.
But actually, most of those things are harmless. What really causes allergic reactions is your immune system. It mistakes innocent things in your surroundings for a serious threat and attacks them. The symptoms you get are the result.
Children with one allergic parent have a 33% chance of developing allergies. With two allergic parents, it’s a 70% chance.
Even so, the circumstances have to be just right for something to trigger an allergic reaction.
Other things may also be involved. For instance, if you come into contact with an allergen when you’re weak, such as after a viral infection — you might be more likely to develop an allergy to it.
How an Allergy Starts
It begins with exposure. Even if you’ve been around a trigger (or “allergen,” as your doctor calls it) many times before with no trouble, your body may suddenly see it as an invader. If this happens, your immune system studies the allergen and makes antibodies against it, in case the same situation happens again.
Then, the next time you come across that allergen, your immune system takes action. The antibodies recognize it and turn on special cells called mast cells.
The mast cells burst open, releasing chemicals such as histamine that cause symptoms such as swelling. Swelling in your nasal passages might cause a runny nose. Swelling in the airways could cause asthma symptoms.
Keep in mind that the amount of exposure can make a difference. If you’re allergic to strawberries, you may have been able to eat one or two without symptoms. But once you eat three or four, you suddenly break out in hives. There’s a tipping point — or threshold — for people with allergies. You can handle some exposure, but too much launches an immune system attack.
The problem is that you can’t predict how you’ll recover. So if you have a food allergy, you should avoid your trigger foods completely.
Treatments
Immunotherapy in the form of allergy shots or pills under the tongue, which gradually increase your ability to tolerate allergens, are also available.
Antihistamines
Antihistamines have been used for years to treat allergy symptoms. They can be taken as pills, liquid, nasal spray, or eye drops. Over-the-counter (OTC) antihistamine eye drops can relieve red itchy eyes, while nasal sprays can be used to treat the symptoms of seasonal or year-round allergies.
Examples of antihistamines include:
- Over-the-counter:Cetirizine (Zyrtec), fexofenadine (Allegra), levocetirizine (Xyzal), and loratadine (Alavert, Claritin) are taken by mouth. Brompheniramine (Dimetapp allergy, Nasahist B), chlorpheniramine (Chlor-Trimeton), clemastine (Tavist), and diphenhydramine (Benadryl) can make you drowsy. Ketotifen (Zaditor) and naphazoline and pheniramine combination ophthalmic (OcuHist) are eye drops.
- Prescription: Desloratadine (Clarinex) is a medication taken by mouth. Azelastine nasal (Astelin) is a nasal spray. Eye drops include azelastine ophthalmic (Optivar), epinastine ophthalmic (Elestat), and olopatadine ophthalmic (Patanol).
How Do Antihistamines Work?
When you are exposed to an allergen — for example, ragweed pollen — it triggers your immune system. People with allergies have an exaggerated immune response. Immune system cells known as “mast cells” release a substance called histamine, which attaches to receptors in blood vessels, causing them to enlarge. Histamine also binds to other receptors causing redness, swelling, itching, and changes in secretions. By blocking histamine and keeping it from binding to receptors, antihistamines prevent these symptoms.
What Are the Side Effects of Antihistamines?
Many older over-the-counter antihistamines may cause drowsiness. Newer antihistamines that don’t make you drowsy are available over-the-counter and by prescription.
Decongestants
Decongestants relieve congestion and are often prescribed along with antihistamines for allergies. They can come in nasal sprays, eye drops, liquids, and pills.
Nasal spray and eye drop decongestants should be used for only a few days at a time because long-term use can make symptoms worse. Pills and liquid decongestants can be taken longer safely.
Some examples of decongestants that are available over-the-counter include:
- Pseudoephedrine (Sudafed tablets or liquid)
- Phenylephrine (Neo-Synephrine) and oxymetazoline (Afrin) nasal sprays
- Some Visine eye drops
How Do Decongestants Work?
During an allergic reaction, tissues in your nose may swell in response to contact with the allergen. That swelling makes fluid and mucus. Blood vessels in the eyes can also swell, causing redness. Decongestants work by shrinking swollen nasal tissues and blood vessels, relieving the symptoms of nasal swelling, congestion, mucus secretion, and redness.
What Are the Side Effects of Decongestants?
Decongestants may raise blood pressure, so they typically are not recommended for people who have blood pressure problems or glaucoma. They may also cause insomnia or irritability and restrict urinary flow.
Combination Allergy Drugs
Some allergy drugs contain both an antihistamine and a decongestant to relieve multiple allergy symptoms. Other drugs have multiple effects aside from just blocking the effects of histamine, such as preventing mast cells from releasing other allergy-inducing chemicals.
Some examples of combination allergy medicines include:
- Over-the-counter:cetirizine and pseudoephedrine (Zyrtec-D), fexofenadine and pseudoephedrine (Allegra-D), diphenhydramine and pseudoephedrine (Benadryl Allergy and Sinus), loratadine and pseudoephedrine (Claritin-D), and pseudoephedrine/ triprolidine (Actifed) for nasal allergies; and naphazoline/pheniramine (Naphcon A) for allergic conjunctivitis
- Prescription: acrivastine and pseudoephedrine (Semprex-D) for nasal allergies; azelastine/fluticasone (Dymista) combines an antihistamine with a steroid in a nasal spray for seasonal nasal allergies
Anticholinergic Nasal Sprays
The drug Ipratropium bromide (Atrovent) can reduce runny nose. When sprayed into each nostril, it lessens mucus from the glands lining the nasal passages.
What Are the Side Effects of Anticholinergic Nasal Sprays?
They may cause a very dry nose, leading to nosebleeds or irritation. Other side effects include headaches, stuffy nose, upset stomach, and sore throat.
Steroids
Steroids, known medically as corticosteroids, can reduce inflammation associated with allergies. They prevent and treat nasal stuffiness, sneezing, and itchy, runny nose due to seasonal or year-round allergies. They can also decrease inflammation and swelling from other types of allergic reactions.
Systemic steroids are available in various forms: as pills or liquids for serious allergies or asthma, locally acting inhalers for asthma, locally acting nasal sprays for seasonal or year-round allergies, topical creams for skin allergies, or topical eye drops for allergic conjunctivitis. In addition to steroid medications, your doctor may decide to prescribe additional types of medications to help combat your allergic symptoms.
Some steroids include:
- Prescription nasal steroids: beclomethasone (Beconase, Qnasl, Qvar), ciclesonide (Alvesco, Omnaris, Zetonna), fluticasone furoate (Veramyst), and mometasone (Nasonex)
- Over-the-counter nasal steroids: budesonide (Rhinocort Allergy), fluticasone (Flonase Allergy Relief), and triamcinolone (Nasacort Allergy 24HR)
- Eye drops: dexamethasone ophthalmic (Maxidex), and loteprednol ophthalmic (Alrex)
- Oral steroids: prednisone (Deltasone)
What Are the Side Effects of Steroids?
Steroids have many potential side effects, especially when taken for a long time.
Side effects of systemic steroids with short-term use include:
- Weight gain
- Fluid retention
- High blood pressure
Side effects with long-term use include:
- Growth suppression
- Diabetes
- Cataracts of the eyes
- Bone-thinning osteoporosis
- Muscle weakness
Side effects of inhaled steroids may include cough, hoarseness, or fungal infections of the mouth.
Mast Cell Stabilizers
Mast cell stabilizers treat mild to moderate inflammation.
Mast cell stabilizers are available as eye drops for allergic conjunctivitis, and nasal sprays for nasal allergy symptoms. Like with many drugs, it may take several weeks before the full effects are felt.
Some examples of mast cell stabilizers include:
- Cromolyn sodium (Opticrom)
- Lodoxamide-tromethamine (Alomide)
- Nedocromil (Alocril)
- Pemirolast (Alamast)
How Do Mast Cell Stabilizers Work?
Mast cell stabilizers prevent the release of histamine from mast cells (cells that make and store histamine). Some of these drugs also have important anti-inflammatory effects, but typically they are not as effective as steroids.
What Are the Side Effects of Mast Cell Stabilizers?
Throat irritation, coughing, or skin rashes sometimes happen. Mast cell stabilizers in the form of eye drops may cause burning, stinging, or blurred vision.
Leukotriene Modifiers
Leukotriene modifiers treat asthma and nasal allergy symptoms. They can be prescribed along with other drugs.
These medications are available only with a doctor’s prescription and come as pills, chewable tablets, and oral granules.
The only leukotriene modifier that has FDA approval is montelukast (Singulair).
How Do Leukotriene Modifiers Work?
Leukotriene modifiers block the effects of leukotrienes, chemicals produced in the body in response to an allergic reaction.
What Are the Side Effects of Leukotriene Modifiers?
Side effects of these drugs are rare but may include:
- Stomach pain or stomach upset
- Heartburn
- Fever
- Stuffy nose
- Cough
- Rash
- Headache
- Irritability
Other Over-the-Counter Products
Some simple over-the-counter products can help with allergy symptoms. They include:
- Saltwater solution, or saline, is available as a nasal spray to relieve mild congestion, loosen mucus, and prevent crusting. These sprays contain no medicine.
- Artificial tears, which also contain no medicine, are available to treat itchy, watery, and red eyes.
Immunotherapy
Immunotherapy may be one of the most effective forms of treatment if you suffer from allergies more than 3 months of the year. Allergy shots expose you to gradually increasing levels of the offending allergen to help your immune system build tolerance.
The FDA has approved several under-the-tongue immunotherapy tablets that can be taken at home. The prescription tablets, called Grastek, Oralair, and Ragwitek, treat hay fever and work the same way as shots. The goal is to boost a patient’s tolerance of allergy triggers. Odactra is an under-the-tongue medication that can relieve symptoms of allergies to dust mites. Palforzia treats peanut allergy.
