Allergy Symptoms

Allergies can cause a range of symptoms. Your signs and symptoms will depend on the type of allergy you have. You may also react differently to the same allergen at different times.

Symptoms of a food allergy may include:

Tingling or itching in the mouth
Swelling of the lips, tongue, face, throat, or other body parts
Hives, itching, or eczema
Wheezing, nasal congestion, or trouble breathing
Stomachache, diarrhea, nausea, or vomiting
Dizziness, lightheadedness, or fainting
Anaphylaxis, a severe, life-threatening allergic reaction that can affect breathing and cause shock

An insect bite or sting allergy may cause any of the following symptoms:

Pain
Redness
Swelling (at the sting site and sometimes other parts of the body)
Flushing
Hives
Itching
Anaphylaxis

Allergic reactions to medication may lead to:

Itchy skin
Hives — small red spots especially on the chest, back, or abdomen — or other rashes
Swelling, particularly in the face
Breathing problems
Anaphylaxis

Airborne allergies (such as to pollen) can cause allergic rhinitis (hay fever), which is characterized by the following:

Itchy nose, mouth, eyes, throat, skin, or any body part
Difficulty with smell
Runny nose
Sneezing
Watery eyes

Other symptoms may develop later, including:

Stuffy nose
Coughing
Clogged ears and reduced ability to smell
Sore throat
Dark circles or puffiness under the eyes
Sleep disturbances, leading to fatigue and irritability
Headache

Allergy Triggers

If you suspect you have allergies, keep a record of your symptoms, including when they start and what seems to trigger them. Information about potential allergy triggers will help your doctor when taking your medical history.

The reason why people’s allergy symptoms are triggered by different things (allergens) has to do with certain antibodies produced by the body’s immune system.

Antibodies known as immunoglobulin E (IgE) are produced when the immune system overreacts to allergens.

They set off a cellular chain reaction resulting in an allergic reaction. Each type of IgE has a “radar” for a specific allergen, so the allergic reaction is a response to that particular trigger.

There are many things that can cause allergies. Some of the most common allergens include:

Pollen

Pollen grains are tiny, reproductive cells produced by plants. Many species of trees, grasses, and weeds produce pollen, which is then carried by the wind and can cause allergic rhinitis.

Pollen is one of the most common triggers of seasonal allergies.

These allergies typically occur in early spring, summer, and fall, but can occur at different points in the year depending on weather conditions and where you live.

Pets

Allergic reactions to cats and dogs affect approximately 3 out of 10 people with allergies.

Animal fur or hair, contrary to common misconception, is not a significant cause of allergies. But it can collect dust, mold, pollen, and other allergens. More commonly, pet dander (dead skin cells), saliva, and urine may trigger an allergic reaction, according to one article.

Cat allergies are about twice as common as dog allergies.

While some breeds may be more allergy-friendly than others, there is no such thing as a hypoallergenic dog or cat.

Food

More than 170 foods can cause allergies, but 90 percent of all food allergens fall into certain groups, including fish, shellfish, eggs, milk, wheat, soy, tree nuts (pecans, walnuts, almonds, cashews, Brazil nuts, pistachios, hazelnuts, and macadamia nuts), and peanuts, noted an article.

An estimated 8 percent of U.S. children have food allergies, according to a survey.

Mold

Mold, a type of fungi, can live almost anywhere, and it thrives in damp environments.

Mold spores (which are even smaller than pollen) are released into the air, where they spread via wind or humidity and can be inhaled.

Although there are many types of mold, only a few cause allergies. When found indoors (usually in bathrooms, kitchens, and basements), they can cause allergy symptoms year round.

Cockroaches

Cockroaches and their droppings are a common trigger for allergies and asthma. Studies show that children who are allergic and exposed to cockroaches need to go to the hospital for asthma more than other children with asthma.

Dust Mites

Dust mites are tiny, eight-legged creatures too small to see with the naked eye. They are also one of the most common triggers of year-round allergies. Dust mites feed on tiny bits of human skin. Humans shed approximately 1.5 grams (g) of skin cells daily, which is enough to feed one million dust mites.

Insect Bites and Stings

Most people recover from an insect bite or bee sting in a matter of hours or days with minor pain, itching, and swelling at the site.

Stinging insects inject tiny amounts of venom, which can cause a life-threatening reaction in people who are allergic. Stings from five insects — honeybees, hornets, wasps, yellow jackets, and fire ants — are commonly known to cause allergic reactions.

Fortunately, most biting insects, such as mosquitoes or fleas, rarely cause extreme reactions.

Latex

Latex is a natural rubber used in products such as balloons and disposable gloves. A latex allergy can cause a mild allergic reaction (swelling, redness, and itching) from skin contact.

In rare cases, latex can cause hives, difficulty breathing, or even anaphylaxis.

Less than 1 percent of Americans have a latex allergy. It’s more common among healthcare workers and others who regularly wear latex gloves. Individuals who have undergone multiple surgical procedures over their lifetime, especially children with spina bifida, are at increased risk as well. Synthetic latex found in paint does not cause allergies.

Medication

Medication can cause both allergic and nonallergic reactions. Allergic reactions can be mild (such as a skin rash or nasal symptoms) or life-threatening (anaphylaxis).

All medication can cause side effects, but only 5 to 10 percent of adverse reactions are allergic.

Allergy Tests

To diagnose allergies, your doctor will first review your medical and family history. A physical examination, which may include an X-ray or lung function test, can also help spot allergy signs or symptoms.

Your doctor may then recommend one or more of the following allergy tests:

Skin Tests

Allergy skin tests are most commonly used for diagnostic purposes. The tests are not foolproof and can produce false-positive or false-negative results.

They are not recommended for people who have had severe allergic reactions or take certain medications such as antihistamines, which can interfere with the results.

Skin prick tests (also known as puncture or scratch tests) involve applying drops of sterile allergen extract to the skin (usually the arm or the back), which are then pricked into the skin with a needle or lancet.

Approximately 50 allergens can be tested for at once. If the patient is allergic to one of the substances, a red, itchy bump (wheal) develops at the site.

In some cases, particularly when testing for allergies to penicillin or insect venom, the allergen may be injected into the skin on the arm (known as an intradermal test).

A patch test may be used when testing for allergens that cause skin irritation or rashes (also called contact allergy). Instead of pricking or injecting the skin, patches are worn for a period of time on the back to expose the skin to potential allergens.

Blood Test

Allergy blood tests measure the amount of lgE antibodies in the blood.

A total IgE test measures the overall number of IgE antibodies in the blood, and an elevated result may indicate an allergic sensitivity. A specific IgE test measures the level of IgE antibodies in response to individual allergens, and it can help identify a specific allergy.

The radioallergosorbent test (RAST) used to be the standard allergy blood test, but another test method known as enzyme-linked immunosorbent assay (ELISA) is more commonly utilized today, notes one article.

Food Challenges

If you’re suspected of having a food allergy, your doctor may suggest keeping a diary of symptoms and triggers to identify the foods that are causing your reaction.

You may be asked to eliminate certain foods from your diet and then consume them again to determine whether they're problematic.

To diagnose or rule out a food allergy, your physician may have you slowly eat a certain type of food in gradually increasing amounts.

Known as an oral food challenge, this is done under strict medical supervision.

Additional reporting by Lynn Marks.

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