All About Allergies
What is an allergy?
A person with an allergy has an overactive immune system. When people have an allergy, their immune system reacts to harmless things, such as grass pollen, pet fur, or a specific food. Something that is normally harmless but causes a reaction is called an allergen.
What causes allergies?
The human immune system is the body’s defense against sickness and infection. It tries to prevent germs, allergens and foreign substances from entering the body and then works to eliminate any that get through.
In people with allergies, the usual way the immune system treats things like pollen, mold, dust mites or animal dander is changed, and the body identifies these as dangerous invaders. Then, your immune system creates a specific IgE antibody to fight it if the allergen enters your body again.
How does an allergic reaction occur?
When you come in contact with the same allergen later, the body is ready to respond with its protective IgE antibodies for that allergen. The antibodies attach themselves to white blood cells called mast cells that line the mucous membrane of the nose, eyes and lungs and cause inflammation. Cilia, the tiny hairs that trap and sweep allergens out of the way, become bogged down with mucus and fluid and allergy symptoms appear.
Are allergies serious?
Allergies are not just a nuisance – they are a serious health issue. Allergies can interfere with day-to-day activities and impact quality of life. They generally fall into two categories:
- dust mites
- dust mites
Some allergens that can lead to serious, life-threatening allergic reactions (called anaphylaxis) as a result of exposure. These allergens are commonly:
- insect venom
Are allergies genetic?
As many at 50 million people in the United States have some type of allergy. The tendency to develop allergies is often – but not always – hereditary, passed down from generation to generation. However, not everyone in a family will be allergic to the same things – and some won’t be allergic at all.
What are the most common allergy symptoms?
Allergy symptoms vary from person to person and each allergy. Seasonal or environmental allergy symptoms include:
- Runny nose, usually with clear or pale-colored mucus
- Red, watery eyes
- Itching around the nose, mouth or eyes
Left untreated, these symptoms can lead to other issues like nasal congestion, headaches, sore throats, and other issues, so treatment is important.
Allergy symptoms can also be very serious and life-threatening, leading to anaphylaxis. Symptoms that may require you to seek emergency care include:
- Skin: itching, redness, swelling and hives
- Mouth: itching, swelling of lips and tongue
- Stomach: vomiting, diarrhea, cramps
- Respiratory: shortness of breath, wheezing, coughing, chest pain and/or tightness
- Heart: weak pulse, dizziness, faintness
- Headache, nasal congestion, watery eyes, sweating
- Confusion, feeling of impending doom
- Loss of consciousness
Can allergies cause a fever?
No, allergies do not cause a fever. Allergies are not caused by a virus and therefore cannot cause a fever. If you experience common allergy symptoms (coughing, sneezing, stuffy or runny nose) along with a fever, then you may be suffering from a cold, flu, bacterial infection or another infection. If you have itchy, watery eyes, then you likely have allergies; itchy, watery eyes are uncommon with a cold or flu virus.
Talking About the Weather
What's the spring allergy outlook where you live? Will sudden temperature changes trigger an asthma flare? Weather can play a key role in allergy and asthma symptoms, as well as flu transmission. Allergy & Asthma Network partnered with Weather Trends International to provide forecasting and analysis for people with asthma and allergies. It compiles information about an area's temperature, anticipated pollen forecast, flu prevalence, and more in determining its forecast.
How are allergies diagnosed and tested?
It is important to know which allergens cause you to have symptoms. To get diagnosed and tested for allergies, you should see a board-certified allergist. This allergist will do the following:
- review your health history and your family’s health history
- ask about the frequency and severity of your symptoms
- ask what activities might expose you to allergens
- ask about your home and work environments
- perform a physical exam of your eyes, ears, nose and lungs
Based upon the findings, the allergist can determine if allergy testing is needed. Allergy testing may include skin prick testing and blood tests. You can then work with your allergist to understand the results and develop a treatment plan.
What allergy medications and treatments are available?
Several treatment options are currently available for allergies including:
- avoidance of allergens
- allergen immunotherapy
- nasal sprays and washes
Medications used to treat allergies include:
- Nasal corticosteroid sprays
- Leukotriene modifiers
- Mast cell stabilizers
Allergen immunotherapy, also known as allergy shots, helps build your tolerance to allergens, reducing or eliminating symptoms. It works by the patient being given a gradually increasing amount of the allergen on a regular schedule, until a maintenance level is reached.
Tolerance for the allergen typically continues after immunotherapy ends – however the long-term success rate varies from person to person.
Allergy shots and under-the-tongue tablets are types of immunotherapy that your allergist may recommend for treatment of your allergies. Visit your allergist to determine the best treatment option for you.
What are the most common allergies?
Many different substances trigger allergic symptoms. Common allergens include:
Eight foods account for 90 percent of all reactions in the United States. These nine foods are known as the “top 9” food allergies:
- cow’s milk
- hen’s eggs
- tree nuts
Pollen allergy is an allergy to pollen, tiny particles released by trees, grasses and weeds. Pollen grains float through the air in spring, summer and fall – or year-round in areas with mild winters.
Symptoms of pollen allergies may be:
- sneezing spells
- watery or itchy eyes
- itchy throat
Pollen allergies may occur throughout the year. Tree pollens are common in late winter and early spring, followed by grasses in late spring and summer. Then towards the end of the summer allergies from the pollen released by weeds such as ragweed are more common.
There are ways to limit exposure to pollen allergens and minimize symptoms. However, pollen allergies may require medications to control symptoms, so treatment options should be discussed with a board-certified allergist.
Molds are microscopic organisms called fungi, found virtually everywhere, indoors and out. Molds reproduce through spores spread by water, insects or air, so tiny and lightweight they can float through the air like pollen. These spores can be inhaled and cause allergic symptoms.
These symptoms include:
- Nasal and sinus congestion
- Sore Throat
- Watery or burning eyes
- Dry cough
- Shortness of breath
- Irritation of the nose, throat, or skin
Mold spores are especially dangerous for people with asthma and may trigger asthma attacks, but the exact reason is not known
Testing for mold allergy is done by a board-certified allergist and may include both skin prick and blood tests.
Treatment for mold allergies includes:
- Nasal corticosteroids
- Montelukast (Singulair)
Mold hides both indoors and outdoors, so limiting exposure is key.
Allergic reactions to cats, dogs and other furry animals are caused by proteins found in flecks of the pets’ skin, called dander, as well as in their saliva and urine. You are really not allergic to the fur of your pet. You are allergic to pet dander.
Pet allergens can cause reactions when they’re inhaled, get in the eyes, or come in contact with skin. Reactions may happen within minutes, but may be delayed for hours.
The best way to eliminate a pet allergy is to remove the pet from the home. However, the pet dander can remain in the home for weeks to months.
Dust mites are tiny insects that live in mattresses, pillows, upholstered furniture. They look for moisture along with their favorite food, tiny bits of shed human skin.
Allergens from dust mite droppings and dead bodies collect in bedding, furnishings and dust, then irritate airways and eyes on contact.
Symptoms of dust mite allergy include:
- itchy eyes,
- scratchy throats,
- runny nose and
- other allergy symptoms
- Dust mites are also a potent trigger of asthma.
There are changes you can make to your home environment to reduce dust mites.
Dust mite allergies can be treated with over-the-counter decongestants, antihistamines, or nasal sprays. Seek care from a board-certified allergist to discuss medications as well as immunotherapy.
Cockroaches and mice are mostly nocturnal, scavenging at night for food and water – and leaving behind trails of allergens that cause symptoms on contact or when inhaled. Cockroach allergens are believed to be feces, saliva and body parts. Mice allergens are skin, saliva and urine.
Allergen levels are usually highest on kitchen cabinets and floors, while moisture-laden bathrooms are secondary areas. Poorly contained food and garbage in kitchens is a well-known risk factor. The bedroom is another prime location for cockroaches, particularly in heavily infested homes.
The best way to remove mice from the home are mouse traps; place them against walls where mice often scurry as they search for food in your home.
For severe infestations, it may be best to call a professional exterminator.
Minor home improvements can improve your chances of keeping cockroaches and mice out.
For most people, insect stings are a short-term annoyance. Others allergic to the venom in a stinging insect can cause an allergic reaction.
The most common insects to cause an allergic reaction are:
- Yellow jackets
- Paper wasps
- Red ants (“fire ants”)
Symptoms of an insect venom allergy can range from a mild local reaction to a severe systemic reaction known as anaphylaxis. The danger is that an allergic reaction can happen to anyone, even people with no other allergies and people who have been stung before with no problems
Localized reactions may be managed at home with cold compresses, antihistamines, or itching creams.
- Severe, life threatening symptoms are:
- Hives or generalized itching other than at the site of the sting
- Swelling of the throat or tongue
- Difficulty breathing
- Severe headache
- Stomach cramps, nausea or diarrhea
If you develop these symptoms, the only treatment is an injection of epinephrine, which should be given first and fast. If you need an injection of epinephrine, you should also follow-up with emergency care.
If you have a known insect allergy you should always carry an epinephrine auto injector.
Eye allergies, also known as allergic conjunctivitis, occur when the protective outer covering of the eye and eyelid, called the conjunctiva, becomes swollen and inflamed due to allergens or irritants.
Common symptoms include:
- red, irritated, teary and itchy eyes
- eyelid swelling
- blurred vision
- sensitivity to light
Environmental triggers and irritants cause eye allergies.
Environmental triggers include:
- Dust mites
- Pet dander
- Cigarette smoke
- Contact lenses
- Contact lens solution
The most effective treatment for eye allergies is avoiding environmental triggers and irritants.
Drug allergies may cause hives, cause light-headedness, nausea, difficulty breathing or stomach cramps, or make your throat or mouth swelling. Symptoms can begin within moments of ingesting a medication or up to several hours later.
Medications that most often cause a reaction include:
- Aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen
- Drugs used in anesthesia
- Insulin (rarely)
- Chemotherapy drugs
If you develop flushing or hives within a few hours of taking a medication, call a board-certified allergist. If symptoms are severe and involve multiple body organs – a skin rash, respiratory problems and/or digestive issues – it could be anaphylaxis. Call 911 and go to the emergency department immediately.
Not all reactions are a drug allergy, so it is important to get tested by a board-certified allergist.
Latex allergy is an allergic reaction to the proteins present in the milky sap of the Hevea brasiliensis rubber tree.
Latex allergy generally develops after repeated exposure to medical and consumer products containing natural rubber latex.
Allergy to latex poses a serious health risk to:
- healthcare workers
- spina bifida patients
- workers with occupational exposure
- patients with multiple surgeries
- the general population
Symptoms of latex allergy may be mild at first, progressing to more serious types of symptoms.
Symptoms of latex allergy include:
- skin redness
- urticaria (hives)
- nasal drainage
- itchy eyes
- throat irritation
A latex allergy reaction can also result in anaphylaxis, a life-threatening allergic reaction.
Do I have allergies or a cold?
Sometimes it is hard to tell if you have allergies, or if your symptoms could be due to a cold, or flu or sinus infection. The following chart can help you tell the difference.
Quick 3-5 minute videos on asthma, allergies, and related conditions.
Are there other conditions that can look like or complicate allergies
There are other types of conditions that can mimic allergies, but are different than an IgE-mediated allergy. The symptoms, diagnosis and treatment can vary depending upon the condition. Here are some of them.
Food-related conditions that can have symptoms similar to food allergies include:
See Related Pages
- Symptoms of Allergies
- Allergy Diagnosis and Testing
- How are Allergies Treated?
- Nasal Allergy, Rhinitis and Allergic Rhinitis
- What if I Can’t Afford My Allergy Medications?
- Pregnancy and Allergies
- Pollen Allergy
- Eye Allergies – Allergic Conjunctivitis
- Mold Allergy
- Allergies to Dogs – Cats – Pets
- Allergy to Dust Mites
- Cockroach and Mice Allergy
- Insect Allergy
- Drug Allergy
- Complete Guide to Latex Allergy
- Allergy Statistics in the US
- Allergy Dictionary
- Allergy Webinars