KATHMANDU: Allergic reactions occur when the immune system overreacts to substances called allergens that come into contact with the skin, nose, eyes, respiratory tract, or gastrointestinal system. Common allergens include poison ivy, fragrances, and medications, which can cause allergic rashes that vary in size and severity depending on their cause.

An allergic reaction happens when the immune system treats substances that are generally harmless as threats. Common allergens include mold, pollen, and certain foods.

Types of Allergic Reactions

There are four types of allergic reactions, each triggered differently and presenting distinct symptoms:

Type I (Immediate or Anaphylactic Reactions): These occur within minutes of exposure to an allergen.
Type II (Antibody-Dependent Reactions): These happen when the immune system attacks part of the body.
Type III (Immune Complex Reactions): Similar to Type II, but involve the immune system attacking other parts of the body.
Type IV (Delayed Hypersensitivity Reactions): These develop 12 to 72 hours after exposure to an allergen.

Causes of Allergic Reactions

The exact causes of allergies remain unclear, but certain substances are commonly known to trigger allergic reactions. People who have allergies may be sensitive to one or more of the following:

• Medications like penicillin and aspirin
• Foods such as shellfish and nuts
• Dust mites
• Certain plants
• Bee stings or insect bites
• Pet dander from animals like cats or dogs

Allergens can enter the body in several ways:

• By inhalation
• Through skin contact
• By ingestion (eating or swallowing)
• Through injection

Risk Factors

Several factors increase the likelihood of developing allergies, including:

• Poor hygiene
• Genetics (family history of allergies)
• Exposure to allergens like pollen, dust mites, mold, and pet dander
• Occupation (frequent exposure to allergens like medicine, metal, or various dusts)
• Nutrition (unhealthy diet including processed foods, fast foods, and unhealthy fats)
• Insect stings
• Stress and fatigue
• Drug use

Symptoms

Mild Allergic Reaction
Symptoms of a mild allergic reaction may include:

• Rash
• Itching
• Allergic rhinitis
• Itchy or watery eyes
• Scratchy throat
• Sneezing
• Nasal congestion

Severe Reaction
Severe allergic reactions, such as those triggered by food, insect stings, or medications, may cause:

• Diarrhea
• Nausea
• Vomiting
• Abdominal pain
• Difficulty swallowing
• Wheezing
• Chest pain
• Dizziness
• Heart palpitations
• Fear
• Weakness
• Loss of consciousness

A severe allergic reaction known as anaphylaxis can develop within seconds and can be life-threatening. Symptoms include:

• A sudden and severe drop in blood pressure
• Difficulty breathing
• Swelling of the airways

Anaphylaxis requires immediate medical attention, as it can result in death without treatment.

Diagnosis

If someone suspects they have an allergy, a doctor can help identify the allergen. The person should be prepared to explain:

• What triggers the allergic reaction
• Symptoms experienced
• Family history of allergies
• The frequency and timing of the reactions
• Whether others in the household experience similar reactions

Doctors may recommend tests such as:

• Skin prick tests
• Blood tests to check for IgE antibodies
• Patch tests

Treatment

While there’s no cure for allergies, treatments can help manage symptoms. The best way to manage an allergy is to avoid allergens, though this isn’t always possible.

Medication options include:

• Decongestants: Help relieve nasal congestion.
• Antihistamines: Block histamine, a substance the immune system releases during a reaction.
• Corticosteroids: Available in pill, nasal spray, or cream form, these reduce inflammation.
• Leukotriene receptor antagonists: Help with some allergies when other treatments fail.
• Immunotherapy: Helps a person develop long-term tolerance to allergens.

Prevention

To prevent allergic reactions:

• Avoid exposure to known allergens
• Keep windows closed during peak allergy season
• Clean your house frequently
• Carry medications for anaphylaxis treatment
• Undergo allergy testing to identify allergens to avoid
• Seek medical care if exposed to an allergen

Complications

Possible complications from allergic reactions include:

• Life-threatening reactions (anaphylaxis)
• Breathing difficulties
• Side effects from medications (such as drowsiness)
• Allergic conjunctivitis
• Sinus, ear, or lung infections
• Swelling