Allergy Symptoms

Allergies occur when your immune system has a reaction to a normally harmless foreign substance (known as an allergen) such as dust, pollen, or food, resulting in physical symptoms that can range from mild to life-threatening.

Allergy symptoms and their severity vary from person to person, and more than one substance can trigger an allergic reaction in someone. There are mild, moderate, and severe categories of allergy symptoms.

This article will look at mild, moderate, and severe allergy symptoms and how to tell if it's an allergy or sickness causing your symptoms.

Person using laptop at home and holding tissue to runny nose

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Mild Allergy Symptoms

Mild allergic reactions usually occur only in the parts of the body that come into direct contact with the allergen.

There are seven main symptoms that are typical of mild allergies. They include:

How the allergen enters your body will determine the type of symptoms you'll have. Allergens usually enter the body in one of four ways, as follows:

Moderate Allergy Symptoms

Allergy symptoms usually start off as mild but can become worse over time. Moderate allergic reactions are worse than mild reactions, but not as serious as severe reactions.

Moderate allergic reactions can include these symptoms:

  • Facial swelling, swollen lips, or tongue (angioedema)
  • Widespread rash or itchiness
  • Hives
  • Cough
  • Wheezing or difficulty breathing
  • Nausea and vomiting
  • Asthma symptoms or asthma attack (in allergic asthma)

Severe Allergy Symptoms

Severe allergy symptoms are serious and can worsen quickly into anaphylaxis, a life-threatening allergic reaction that usually affects more than one part of the body such as the lungs, heart, skin, or digestive system.

Anaphylaxis is an emergency that can cause death in less than 15 minutes. The only way to reverse symptoms is with an epinephrine (EpiPen) injection. If you or someone you know is having a severe allergic reaction, assume it’s an anaphylactic reaction and take action by administering an epinephrine injection (if available), and calling 911 immediately.

Signs of anaphylaxis include:

  • Itchy, red, or swollen skin; or hives
  • Itchy mouth or swelling of the lips and tongue that make swallowing difficult
  • Vomiting, diarrhea, or cramps
  • Severe shortness of breath, wheezing, or coughing
  • Chest tightness or pain
  • Dizziness, faintness, or weak pulse
  • Headache
  • Sweating
  • Confusion
  • Feeling of impending doom
  • Loss of consciousness

Common Anaphylaxis Causes

The most common causes of anaphylaxis are:

How to Tell If It's Allergies or If You're Sick

It can be hard to tell if you are sick with a cold or flu or have allergies, because all three can share similar symptoms such as congestion, runny nose, and sore throat. But there are some differences that can help you tell whether your symptoms are from allergies or being sick.

How Long Symptoms Last

Colds and flu are caused by viruses, and symptoms usually only last one to two weeks while your body is fighting the virus. Allergy symptoms last as long as you’re exposed to the allergen. With seasonal allergies (such as pollen), that can be weeks or months.

Types of Symptoms

Both colds and flu can cause fever, but allergies do not cause fever. You can also feel extreme
exhaustion with the flu, but not with allergies or a cold. Allergies also often cause itchy, watery eyes, which typically aren’t present with a cold or flu.

Is It COVID-19 or Allergies?

COVID-19 and allergies also share certain similar respiratory symptoms like sore throat and
congestion. But COVID frequently has symptoms that you won’t have with allergies. They include:

  • Fever
  • Body aches
  • Fatigue
  • Nausea, diarrhea, or upset stomach
  • Loss of taste or smell

When to See a Healthcare Provider

If you’re experiencing allergy symptoms more than a few months out of the year or if symptoms are affecting your quality of life, daily activities, or sleep, you should contact a healthcare provider. You should also call a healthcare provider if over-the-counter (OTC) medicines aren’t controlling your symptoms or causing more than mild side effects.

A healthcare provider can help diagnose whether you have allergies and to which allergens. They can advise you on how best to avoid those allergens and what treatments are available.

Summary

Allergies are very common and can cause a wide range of symptoms depending on the type
and severity of the allergy. Allergy symptoms are categorized as mild, moderate, or severe. A severe allergic reaction can cause anaphylaxis, a life-threatening medical emergency requiring emergency treatment.

Allergies can also have symptoms that are similar to those of colds, flu, and COVID-19. However, the presence or absence of certain symptoms, such as fever, upset stomach, and body aches, can help you determine which condition you have.

You should contact a healthcare provider if your allergies affect your daily life or you’re not finding relief from OTC medications.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American College of Allergies, Asthma & Immunology. Allergies 101.

  2. Allergy & Asthma Network. Allergy symptoms.

  3. Institute for Quality and Efficiency in Health Care. Allergies: overview.

  4. Asthma and Allergy Foundation of America. Allergy symptoms.

  5. Allergy & Asthma Network. What is anaphylaxis?

  6. Worm M, Eckermann O, Dölle S, et al. Triggers and treatment of anaphylaxis: an analysis of 4,000 cases from Germany, Austria and Switzerland. Dtsch Arztebl Int. 2014;111(21):367-375. doi:10.3238/arztebl.2014.0367

  7. National Institutes of Health News in Health. Cold, flu, or allergy?

  8. American College of Emergency Physicians. How COVID-19 symptoms compare to allergies.

  9. American College of Allergy, Asthma, & Immunology. When to see an allergist.

By Cathy Nelson
Cathy Nelson has worked as a writer and editor covering health and wellness for more than two decades. Her work has appeared in print and online in numerous outlets, including the Detroit Free Press and The Detroit News.