Allergies

Allergy Symptoms and Diagnosis

Different types of allergies cause different symptoms. Here are some of the most common allergic reactions, plus information on diagnosis and testing.

Kathleen Hall
By Medically Reviewed by 
Reviewed:
Medically Reviewed
a woman with allergy symptoms
Allergies cause a range of symptoms, ranging from runny nose to hives to breathing problems to in severe cases, shock. Leo Patrizi/Getty Images
More than 60 million Americans suffer from allergies every year, according to the Centers for Disease Control and Prevention (CDC).

Anyone can have or develop allergies, which are the sixth leading cause of chronic illness in the United States, per the American College of Allergy, Asthma, and Immunology (ACAAI).

As common as allergies are, diagnosing them isn’t always simple.

Diagnosis of allergies involves several factors such as identifying an individual’s symptoms and when they occur, reviewing family and medical history, undergoing a physical examination, and testing.

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.

According to Mayo Clinic, 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
Per the ACAAI, an insect bite or sting allergy may cause:

  • Pain
  • Redness
  • Swelling (at the sting site and sometimes other parts of the body)
  • Flushing
  • Hives
  • Itching
  • Anaphylaxis
According to the American Academy of Allergy, Asthma, and Immunology (AAAAI), 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
Per MedlinePlus, airborne allergies (such as to pollen) can cause allergic rhinitis (hay fever), which is characterized by:

  • 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, explains the AAAAI.

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 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, notes MedlinePlus.

Pollen is one of the most common triggers of seasonal allergies, per the Asthma and Allergy Foundation of America (AAFA).

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, notes AAFA.

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 January 2016 article published in F1000Research.

Cat allergies are about twice as common as dog allergies, per AAFA.

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 published in Clinical and Translational Allergy.

An estimated 8 percent of U.S. children have food allergies, according to a survey published in December 2018 in Pediatrics.

Mold

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

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. According to the AAFA, 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. According to the AAFA, 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 known to cause allergic reactions, notes the ACAAI.

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, per AAFA.

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 bifada, 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, notes the AAAAI.

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, per the Mayo Clinic.

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, explains MedlinePlus.

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 an article published in 2017 in Methods in Molecular Biology.

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, explains AAAI.

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

Additional reporting by Lynn Marks.

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