What Are the Four Types of Allergic Reactions?
Allergic reactions can come in many different forms and for many different reasons. Learn more about the four most common types of allergic reactions and how they can affect you.
When your body is hypersensitive to certain stimuli, its negative response can be classified into four distinct types of allergic reaction: anaphylactic, cytotoxic, immunocomplex, or cell-mediated. Each one is triggered in different ways and can manifest differently in each person. It’s important to monitor the severity of the reaction, no matter the type of allergic response, and to get the allergic person to the hospital as soon as possible if symptoms become dangerous or don’t improve.
What Is an Allergic Reaction?
Our bodies are exposed to all kinds of stimulants and irritants throughout the day, but usually we carry on without being affected by microscopic allergens or food sensitivities. However, it’s common for the body to develop a hypersensitivity to certain irritants, resulting in an a-typical response, or what we commonly call an allergic reaction. There are many different irritants that can spur an allergic reaction, but some of the most common allergy triggers are:
- Pollen and grass
- Insect stings/bites
- Certain medications
- Foods (Milk, shellfish, nuts, etc)
- Pet dander
An allergic reaction starts when you come into contact with an allergen—touching, breathing it in, or consuming it. When this happens, your body responds by making a type of protein molecule called immunoglobulin E, or IgE, that binds with the allergen, creating an antigen-antibody reaction. This binding causes the body to release chemicals (like histamine), which is what causes symptoms like itchy eyes, congestion, and rashes.
The Four Types of Allergic Reactions
Allergic reactions are classified into 4 different categories: Type I, II, III, and IV. Types I, II, and III are immediate allergic reactions, occurring within 24 hours of exposure to the allergen. Type IV reactions, also called delayed allergic reactions, usually appear after 24 hours of exposure.
Type I, or anaphylactic reactions are the most common allergic responses and are triggered by allergens like pollen, dust mites, animal dander, and certain foods. In a Type I reaction, your body releases histamine and other chemicals that cause swelling and inflammation in the body. Common anaphylactic reactions include:
Food allergy: If you have a food allergy, you may experience symptoms immediately after eating, or it could take up to two hours. Symptoms can include swelling of the mouth, face, lips, and throat. Other signs of an allergic reaction are itching, hives, and nasal congestion. The most severe food allergy reaction is called anaphylaxis and it is life threatening. This kind of response can cause difficulty breathing, instant drop in blood pressure, and shock. Anaphylaxis must be treated with an epinephrine injection and should be treated as a medical emergency.
Skin allergy: Skin allergies appear as rashes and are divided into two types—eczema and urticaria. Eczema, or atopic dermatitis, is characterized by dry, red, itchy skin. It can begin during childhood, adolescence, or adulthood and can range from mild to severe. Urticaria, or hives, is a red, itchy, bumpy rash. Usually it lasts no more than 24 hours but it can be very uncomfortable. Hives can appear anywhere on your body in varying shapes and sizes.
Allergic rhinitis: Commonly called hay fever, allergic rhinitis occurs when your immune system overreacts to an inhaled allergen (like mold, pollen, dogs, or cats). Common symptoms include a runny nose, itchy eyes, congestion, and sneezing.
Asthma: Allergic asthma occurs when you inhale an allergen (like tobacco smoke, pollen, dust mites, or strong odors). This leads to swelling inside the airways of the lungs and makes breathing difficult.
Type II, or cytotoxic reactions occur when IgG or IgM antibodies bind with antigens on the cell surfaces. This causes a chain of reactions that leads to cell death, with symptoms occurring after minutes or hours of exposure to the allergen. Type II reactions cause conditions like:
- Autoimmune hemolytic anemia
- Immune thrombocytopenia
- Autoimmune neutropenia
- Goodpasture syndrome
- Graves’ disease
- Myasthenia gravis
Type III, or immunocomplex reactions, are also linked to IgG and IgM antibodies. When these antibodies bind with antigens, they form immunocomplexes that settle on tissues and organs. The body’s attempt to remove these complexes damages the underlying tissue. Symptoms set in after several hours of exposure. Examples of Type III allergic reactions include:
- Rheumatoid arthritis
- Serum sickness
- Arthus reaction
Type IV, or cell-mediated allergic reactions are also called the delayed type of allergic reactions because symptoms manifest at least 24 hours after contact with the allergen. Oftentimes, an allergic reaction won’t occur until 48-72 hours after exposure. Type IV allergic reaction examples include:
- Tuberculin reactions
- Chronic asthma
- Contact dermatitis
- Fungal infections
Get Help with Allergic Reactions
Allergies come in many forms, triggered by many different things. Whether you’re experiencing mild or severe allergic reactions, these conditions can be distracting and debilitating. An accurate allergy test is the first step to determine all of your potential allergens and find the best route forward. At Advanced ENT & Allergy Center, our allergists will help you uncover the cause of your allergies and offer you treatment plans that can help you experience freedom from your symptoms.