Allergy Symptoms


Allergies affect as many as 60 million people in the United States every year. According to the U.S. Centers for Disease Control and Prevention (CDC), there are 7 million doctor’s office visits every year due to allergy symptoms. It is important to understand your allergy symptoms and what is causing them. That way, you can learn how to avoid exposure and be ready to treat your allergy symptoms if they do occur.

Photo of white mother with her child, in the child's bedroom. She is holding a tissue to the child's nose because of allergy symptoms.

What is an allergic reaction?

Allergy symptoms occur when your immune system overreacts to a typically harmless substance such as pollen, dust mites, or foods. When exposed to this substance (known as a “trigger” or “allergen,”) your body’s immune system will respond:

  • the immune system will release chemicals such as histamine.

  • histamine and other chemicals will result in the symptoms you experience such as itching, hives or sneezing.

This immune system response is called an allergic reaction.

An allergic reaction can range from mild to severe. It is important to understand your allergy symptoms and what is triggering them. That way, you can avoid allergic reactions and have a treatment plan if a reaction occurs.

How do allergens enter the body?

Allergens can enter the body in four different ways:

  • airways – breathing an allergen
  • skin – touching an allergen
  • gastrointestinal tract – ingesting an allergen
  • circulatory system – allergen entering the bloodstream.

Important: Always carry two epinephrine auto-injectors. A 2nd reaction can occur within 5-15 minutes after the 1st dose is administered. 

What are the typical signs of allergies?

Symptoms of allergies vary for each person – and the substance triggering the allergic reaction can vary as well.

Common symptoms include:

  • Sneezing and itchy, stuffy or runny nose(allergic rhinitis)
  • Itchy around the nose, mouth, eyes or roof of mouth
  • Itchy, red, watery or swollen eyes (allergic conjunctivitis)
  • Facial swelling, swollen lips, tongue (angioedema)
  • Itchy skin
  • Skin rashes (allergic contact dermatitis, eczema)
  • Hives
  • Cough
  • Wheezing
  • Shortness of breath
  • Headache
  • Nausea and vomiting
  • Asthma attack
  • Anaphylaxis (a severe allergic reaction)

An untreated allergy may also result in the following:

  • Nasal congestion
  • Headache
  • Sore throat
  • Postnasal drip
  • Decreased sense of smell
  • Sinus infections (also called sinusitis)
  • Ear infections
  • Puffiness or dark circles under the eyes
  • Fatigue

Photo of older Asian man scratching his neck because of allergies.

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What are the symptoms of a severe allergic reaction (anaphylaxis)?

Symptoms of severe allergies are serious, even life-threatening. These symptoms can involve various organ systems – skin, mouth, stomach, respiratory, heart. A severe allergic reaction involving two or more organ systems is called anaphylactic shock or anaphylaxis.

The following signs of a severe allergic reaction and may progress quickly:

  • Skin: itchy skin, redness, swelling and hives

  • Mouth: itchy mouth, swelling of lips and tongue

  • Stomach: vomiting, diarrhea, cramps

  • Respiratory: shortness of breath, wheezing, coughing, chest tightness or pain

  • Heart: weak pulse, dizziness, faintness, low blood pressure

  • Headache, nasal congestion, watery eyes, sweating

  • Confusion, feeling of impending doom

  • Loss of consciousness

See More Information on Anaphylaxis

Photo of woman at a computer with icons representing anaphylaxis triggers

Anaphylaxis is a medical emergency. It is a life-threatening reaction. Anaphylaxis must be treated with an epinephrine injection, followed by emergency care.

People with a history of anaphylaxis should always carry two epinephrine auto-injectors with them wherever they go. They should also wear a medical alert bracelet.

Photo of man shown from the waist to his neck. He is scratching his forearm with his other hand.

What are common causes of allergy symptoms?

Allergy symptoms are typically due to reactions to substances in the environment that trigger symptoms. Environmental allergies can be due to indoor or outdoor allergens.

Allergens can be both naturally occurring (such as mold) and manufactured (such as latex). Common allergens include:


Seasonal allergies are typically caused by exposure to pollen. Pollen are tiny particles released by plants, weeds, grasses and trees at certain times of year. They are most prevalent during the spring and fall. Common triggers for seasonal allergies are grass, birch trees and ragweed. The severity of seasonal allergy symptoms may vary. For some, the symptoms may be no more than a minor annoyance. For others, allergy symptoms may be severe and impact quality of life.


Contrary to popular belief, people who are allergic to pets are not allergic to their hair or fur. Rather, allergic reactions to cats, dogs and other furry animals are triggered by an allergy to dander as well as saliva or urine. Pet dander stays in the air a long time and settles into furniture, curtains, rugs, and other household surfaces. People who are allergic to pets may face constant exposure to their allergen.


Molds are microscopic organisms called fungi, found virtually everywhere, indoors, and out. Mold reproduces through spores spread by water, insects or air. The spores are very lightweight and float through the air. Mold spores are easily breathed in and may trigger an allergic reaction. Mold allergies tend to be very problematic for people with asthma.

Photo of a woman rubbing her eye with her hand. On the photo are some icons of allergy triggers.

Dust mites

A dust mite is a relative of ticks and spiders. They are invisible to the naked eye — They live in mattresses, pillows, carpets, upholstered furniture and house dust. They thrive in warm, humid environments. Allergic reactions are triggered by their droppings and dead carcasses.


Cockroaches are nocturnal scavengers who leave behind allergens in their wake. They prefer warm, moist environments and like to hide in cracks and crevices. Cockroach allergens are believed to be caused by their feces, saliva, and body parts.


Similar to cockroaches, mice come out to scavenge for food and water at night. Mice can squeeze their bodies through very small openings. Mice allergens are their skin, saliva, and urine.


Food allergens are proteins in food. Your immune system overreacts when you eat a certain food that contains one of your allergens, even in small amounts. Most people are diagnosed with food allergies as children. Food allergies can develop in adults as well. Nearly 8% of children and over 10% of adults in the U.S. have been diagnosed with food allergies. Food allergy symptoms can range from mild to severe. Symptoms usually appear within minutes of eating the food, though they can sometimes occur hours later.

Insect bites and stings

Insect bites and stings are a minor annoyance for most people, but for someone allergic to insect venom, it may cause an allergic reaction. Common insects known to cause allergic reactions include yellow jackets, hornets, paper wasps, bees, and red (fire) ants.


Symptoms of a medication allergy may begin within moments of ingesting a medication or up to several hours later. Some of the most common medications to cause allergies include antibiotics (such as penicillin), aspirin and other non-steroidal anti-inflammatory drugs, anesthetics, insulin, and chemotherapy.


Latex allergy normally develops after repeated exposure to products containing natural rubber latex. Medical products, in particular, often contain latex. Healthcare workers and people with frequent exposure to medical products are at risk for developing an allergy.

Other substances

Other substances can be allergy triggers. Examples include:

  • plants
  • lotions and other personal care items
  • nickel jewelry

What should you do if you have allergy symptoms?

If you have allergy symptoms, the most important thing you can do is avoid your known triggers. Discuss treatment options with a doctor.

For some people, over-the-counter medicine may be sufficient in treating allergies. For others, prescription medications and other treatments may be necessary. Partner with your doctor or a healthcare professional to develop a treatment plan.

What should you do if you don’t know the cause of your allergy symptoms?

One of the most important ways to manage allergy symptoms is to avoid triggers. So, what do you do if you don’t know your trigger?

  • Keep a symptom diary – detail when and where you experience symptoms, any new products you have used, foods eaten, etc.
  • Try an over-the-counter allergy medicine (check with your doctor, particularly if you are taking other medications)
  • For severe symptoms – make an appointment with a doctor for testing, diagnosis, and to develop a treatment plan.

Photo of a young man in a yellow hat and grey shirt. He is holding a tissue to his nose as he's about to sneeze.

Is fever a common allergy symptom?

A fever is not a symptom of an allergy. A fever is normally a sign of an infection, either from a bacteria or virus. If you have allergy symptoms as well as a fever, make an appointment with a healthcare provider to discuss your symptoms and determine treatments.

Little girl sneezing

Why do we sneeze?

People sneeze in response to an irritation or tickle in their nose. When the inside of your nose gets a tickle, the nerve endings send a message to the sneeze center in your brain. This transmits a call to an amazingly complex set of muscles to get rid of the tickle quickly.

In a split second, your stomach, chest, diaphragm (the breathing muscle beneath your lungs), vocal cord, throat, face and eyelid muscles flex and … Ah-Choo! At a roaring 600 miles per hour, your body tries to dislodge the pollen, dust, mold, virus or bacteria trapped in your nose. (Children sneeze at about 100 miles per hour.)

Some people sneeze when they breathe cold air. Others sneeze in threes. And still others sneeze when stepping from dark into bright light. If this happens to you, then you have a condition called “photic” (meaning “light”) sneezing.

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:

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