Signs & Symptoms of an Allergic Reaction


Mar 9, 2021


About 30% of adults and 40% of children in the U.S. suffer from allergies, so knowing the signs and symptoms of an allergic reaction can be helpful for just about anyone. As children are more susceptible to having allergies, it’s also important to know what to do if a child has an allergic reaction. Let’s discuss the signs and symptoms of an allergic reaction and when you may need to go to the emergency room to treat a reaction. 

What causes allergic reactions?

An allergic reaction occurs when your immune system has a hypersensitive reaction to substances called allergens. If you are allergic to these substances –– most commonly pollen, dust, food, and animal fur –– your body will trigger an allergic reaction upon contact in the form of swallowing, inhaling, or touching the allergen.

In our daily lives, we are surrounded by many types of allergens that can potentially trigger allergic reactions. For example, you can have an allergic reaction to food or dairy –– see our blog post on lactose intolerance symptoms –– a skin allergy, or an allergic reaction to bug bites.

These signs and symptoms of allergic reactions can range in severity depending on the type of allergic reaction and how allergic to an allergen your body is. There are 4 main types of allergic reactions to note. 

What are the 4 types of allergic reactions? 

  1. Anaphylactic (Type I): With Type I reactions, the symptoms will appear almost immediately and include reactions to pollen, dust, animal dander, and food. These reactions can range from your run-of-the-mill daily allergies to more serious reactions such as anaphylactic shock.
  2. Cytotoxic (Type II): Unlike Type I, these symptoms appear within minutes to hours of contact with the allergen. Your immune system creates antibodies that damage cells by activating what is called the “complement system” to fight off the allergen in your body, leading to inflammation. This cell damage can lead to conditions including anemia (lack of red blood cells) and Graves’ disease (the overproduction of thyroid hormones).
  3. Immunocomplex (Type III): These symptoms appear after several hours. The antibodies react with the allergens to form immune complexes. This is common in diseases like lupus, an autoimmune disease where the person’s immune system attacks vital cells and organs disrupting function. Symptoms can include high fever, abdominal or chest pain, and swelling in the limbs. Medical care should be sought out if these symptoms appear.
  4. Cell-mediated (Type IV): Also known as “delayed hypersensitivity,” the symptoms won’t appear until hours or days after the exposure and are usually connected with bacterial diseases. 

How do you know you are having an allergic reaction?

Common allergic reaction symptoms –– most associated with Type I and II reactions –– include:

  • Runny nose and sneezing 
  • Watery Eyes 
  • Rashes
  • Eczema or hives 
  • Stomach cramping 
  • Nausea or vomiting 
  • Difficulty breathing
  • Eye inflammation 
  • Anaphylaxis (allergic shock)*

*Anaphylactic shock can be quite serious and life-threatening if not treated immediately. Read our article on what to do when someone is in anaphylactic shock for more information.

Severe allergic reaction symptoms include:

  • Swelling of the lips or tongue that indicates throat closure  
  • Shortness of breath
  • Severe skin rashes 
  • Dizziness or fainting
  • Vomiting or diarrhea 
  • Painful cramps 

If you or a loved one have any of these latter, more severe symptoms, these are indicators of when to go to the ER for an allergic reaction

Need to Go to the ER for an Allergic Reaction? Visit a Complete Care Emergency Facility.

Now that we’ve covered the signs and symptoms of an allergic reaction, we hope you have a better understanding of when to head to an emergency room for an allergic reaction. If you have any other questions regarding allergic reactions, Complete Care is here to help. 

We have ER locations in both Texas (Austin, Corpus Christi, San Antonio, Dallas/Fort Worth, East Texas, and Lubbock) and Colorado (Colorado Springs). Whether you have an emergency or just a simple health question, we will take complete care of you.

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