Hypersensitivity refers to an exaggerated or inappropriate reaction of the immune system to a substance that is normally harmless to the body. These reactions can affect the skin, respiratory system, digestive system, or the entire body. Hypersensitivity can range from mild discomfort to severe life-threatening conditions.
The immune system is designed to protect the body from harmful organisms such as bacteria and viruses. However, in hypersensitivity reactions, the immune system mistakenly overreacts to allergens, medications, foods, or environmental substances.
Hypersensitivity is an excessive immune response that causes tissue damage, inflammation, or allergic reactions when the body encounters certain triggers known as allergens or antigens.
These triggers may include:
Dust
Pollen
Animal fur
Foods
Drugs
Chemicals
Insect stings
Latex
Mold
Some people are genetically more prone to hypersensitivity reactions than others.
Types of Hypersensitivity
Hypersensitivity reactions are classified into four major types.
Type I Hypersensitivity (Immediate Hypersensitivity)
This is the most common allergic reaction. It occurs within minutes after exposure to an allergen.
Causes
Pollen
Dust mites
Certain foods
Animal dander
Insect stings
Common Conditions
Asthma
Hay fever (allergic rhinitis)
Eczema
Food allergies
Anaphylaxis
Symptoms
Sneezing
Runny nose
Itchy eyes
Skin rash
Swelling
Difficulty breathing
Severe Reaction: Anaphylaxis
Anaphylaxis is a medical emergency that may cause:
Throat swelling
Drop in blood pressure
Rapid heartbeat
Loss of consciousness
Immediate treatment is required.
Type II Hypersensitivity (Cytotoxic Hypersensitivity)
This occurs when the immune system mistakenly attacks healthy body cells.
Examples
Drug-induced anemia
Blood transfusion reactions
Hemolytic disease of the newborn
Symptoms
Depend on the organ affected but may include:
Fatigue
Jaundice
Fever
Weakness
Type III Hypersensitivity (Immune Complex Hypersensitivity)
This happens when immune complexes accumulate in tissues and cause inflammation.
Examples
Lupus
Rheumatoid arthritis
Serum sickness
Symptoms
Joint pain
Swelling
Fever
Skin rashes
Kidney problems
Type IV Hypersensitivity (Delayed Hypersensitivity)
This reaction develops slowly, usually after 24–72 hours.
Causes
Contact with certain chemicals
Metals like nickel
Poison ivy
Some cosmetics
Common Conditions
Contact dermatitis
Tuberculosis skin test reaction
Symptoms
Redness
Itching
Skin irritation
Blisters
Causes of HypersensitivitySeveral factors may contribute to hypersensitivity reactions.Genetic FactorsFamily history of allergies increases risk.Environmental FactorsExposure to pollution, smoke, dust, and chemicals may trigger reactions.Food AllergensCommon food allergens include:EggsMilkNutsSeafoodWheatSoy
Common Symptoms of Hypersensitivity
Symptoms vary depending on the type and severity.
Skin Symptoms
Itching
Rashes
Hives
Swelling
Redness
Respiratory Symptoms
Sneezing
Wheezing
Nasal congestion
Shortness of breath
Digestive Symptoms
Vomiting
Diarrhea
Stomach cramps
Severe Symptoms
Difficulty breathing
Chest tightness
Dizziness
Fainting
Hypersensitivity refers to an exaggerated or inappropriate reaction of the immune system to a substance that is normally harmless to the body. These reactions can affect the skin, respiratory system, digestive system, or the entire body. Hypersensitivity can range from mild discomfort to severe life-threatening conditions.
The immune system is designed to protect the body from harmful organisms such as bacteria and viruses. However, in hypersensitivity reactions, the immune system mistakenly overreacts to allergens, medications, foods, or environmental substances.
Hypersensitivity is an excessive immune response that causes tissue damage, inflammation, or allergic reactions when the body encounters certain triggers known as allergens or antigens.
These triggers may include:
Dust
Pollen
Animal fur
Foods
Drugs
Chemicals
Insect stings
Latex
Mold
Some people are genetically more prone to hypersensitivity reactions than others.
Types of Hypersensitivity
Hypersensitivity reactions are classified into four major types.
Type I Hypersensitivity (Immediate Hypersensitivity)
This is the most common allergic reaction. It occurs within minutes after exposure to an allergen.
Causes
Pollen
Dust mites
Certain foods
Animal dander
Insect stings
Common Conditions
Asthma
Hay fever (allergic rhinitis)
Eczema
Food allergies
Anaphylaxis
Symptoms
Sneezing
Runny nose
Itchy eyes
Skin rash
Swelling
Difficulty breathing
Severe Reaction: Anaphylaxis
Anaphylaxis is a medical emergency that may cause:
Throat swelling
Drop in blood pressure
Rapid heartbeat
Loss of consciousness
Immediate treatment is required.
Type II Hypersensitivity (Cytotoxic Hypersensitivity)
This occurs when the immune system mistakenly attacks healthy body cells.
Examples
Drug-induced anemia
Blood transfusion reactions
Hemolytic disease of the newborn
Symptoms
Depend on the organ affected but may include:
Fatigue
Jaundice
Fever
Weakness
Type III Hypersensitivity (Immune Complex Hypersensitivity)
This happens when immune complexes accumulate in tissues and cause inflammation.
Examples
Lupus
Rheumatoid arthritis
Serum sickness
Symptoms
Joint pain
Swelling
Fever
Skin rashes
Kidney problems
Type IV Hypersensitivity (Delayed Hypersensitivity)
This reaction develops slowly, usually after 24–72 hours.
Causes
Contact with certain chemicals
Metals like nickel
Poison ivy
Some cosmetics
Common Conditions
Contact dermatitis
Tuberculosis skin test reaction
Symptoms
Redness
Itching
Skin irritation
Blisters
Causes of HypersensitivitySeveral factors may contribute to hypersensitivity reactions.Genetic FactorsFamily history of allergies increases risk.Environmental FactorsExposure to pollution, smoke, dust, and chemicals may trigger reactions.Food AllergensCommon food allergens include:EggsMilkNutsSeafoodWheatSoy
Common Symptoms of Hypersensitivity
Symptoms vary depending on the type and severity.
Skin Symptoms
Itching
Rashes
Hives
Swelling
Redness
Respiratory Symptoms
Sneezing
Wheezing
Nasal congestion
Shortness of breath
Digestive Symptoms
Vomiting
Diarrhea
Stomach cramps
Severe Symptoms
Difficulty breathing
Chest tightness
Dizziness
Fainting