What Are The 4 Types of Allergic Reactions?

Allergic reactions occur when the body’s immune system has a reaction to a substance it sees as harmful, called an allergen. 

In 1963, two British immunologists, Robert Coombs and Philip Gell, classified four different types of hypersensitivity reactions:

• Immediate (type I)
  • Symptoms appear after a few seconds to minutes
    • Anaphylactic reactions: the most severe form of allergic reaction
    • Anaphylaxis is a medical emergency that can lead to sudden, life-threatening respiratory failure
  • Symptoms include difficulty breathing, swelling, low blood pressure, bluish skin, and shock
  • IgE antibodies are produced by the immune system in response to allergens such as pollen, animal dander, insect bites, dust mites, or certain foods
• Cytotoxic (type II)
  • Symptoms appear after minutes to hours
  • IgG and IgM antibodies damage cells by activating the complement system of the immune system such as in:
    • Autoimmune hemolytic anemia
    • Immune thrombocytopenia 
    • Autoimmune neutropenia
    • Goodpasture syndrome
    • Graves’ disease
    • Myasthenia gravis
• Immune complex-mediated (type III)
  • Symptoms set in after several hours
  • IgM and IgG antibodies react with allergens to form immunocomplexes (antigen-antibody complexes) such as in: 
    • Lupus
    • Serum sickness 
    • Arthus reaction
• Delayed hypersensitivity (type IV)
  • Symptoms set in hours to days later
  • Often in long-term infectious diseases such as: 
    • Tuberculosis 
    • Fungal infections

Symptoms of an allergic reaction include:

• Itchy, watery eyes
• Runny nose
• Itchy nose
• Swelling
• Skin redness
• Sneezing
• Rashes
• Hives 
• Stomach cramps
• Vomiting
• Diarrhea
• Bloating
• Pain
• Cough

Call 911 and get to a hospital’s emergency department if you experience any symptoms of anaphylaxis, a severe and potentially life-threatening allergic reaction: 

• Severe skin rashes, itching, or hives
• Swelling of the lips, tongue, or throat (throat closing)
• Shortness of breath
• Wheezing 
• Chest tightness
• Dizziness, lightheadedness, and/or fainting
• Stomach pain, bloating, vomiting or diarrhea
• Uterine cramps
• Sense that something awful is about to happen

Many things can cause allergic reactions. Some of the most common allergy triggers include: 

• Drugs
• Certain foods
• Insect stings/bites
• Latex
• Mold
• Pet dander
• Pollen

The best way to treat allergic reactions is to prevent them by avoiding known allergens. Remove allergens from your home if possible. To reduce symptoms of airborne allergens, you can wash out your nose daily with a squeeze bottle filled with nasal saline rinse or by using a or a Neti pot.

Medicines to treat symptoms of an allergic reaction include:  

• Nasal corticosteroids: most effective for nasal allergies
• Antihistamines: for seasonal and indoor allergies
• Mast cell stabilizers: to help with itchy, watery eyes or an itchy, runny nose
• Decongestants: to reduce stuffiness
  • Do not use nasal decongestant sprays more than three days in a row or you may experience a rebound reaction, where swelling and stuffiness in the nose gets worse
• Corticosteroid creams or ointments: to relieve itchiness and stop the spread of rashes
• Oral corticosteroids: to reduce swelling and stop severe allergic reactions 
• Epinephrine: for life-threatening anaphylaxis (severe allergic reaction)
  • Usually in the form of an epinephrine auto-injector “pen” device
  • Must be used within minutes of the first sign of serious allergic reaction
  • For life-threatening allergic reactions to food, insect stings, latex, and medications