Allergies: Causes, Symptom and Treatment

Introduction

Allergies are reactions from the immune system that happen when the body reacts strongly to things that are usually safe for most people.

These things are called allergens and can be food, pollen, mold, pet fur, dust mites, bug bites, and some medicines. In an allergic reaction, the immune system wrongly sees a safe item as dangerous, causing the release of chemicals like histamine.

Some people get allergies when they are young, while others develop them later. Managing allergies often means avoiding allergens, taking medicine, or sometimes getting immunotherapy (allergy shots) to help lessen the immune response to certain allergens.

Causes

Allergies happen because of an abnormal reaction from the immune system to substances in the environment or diet. The immune system usually defends the body against harmful germs but wrongly thinks harmless allergens are threats.

The main causes of allergies include:

• Genetic Factors: Family history is important in allergies. If someone has relatives with asthma, hay fever, or eczema, they are more likely to have allergies too. Specific genes that control immune response, like those affecting IgE (immunoglobulin E) levels, increase the chance of developing allergies.
• Environmental Factors: Contact with allergens in the environment is key in growing and worsening allergic issues. Common allergens comprise:
• Pollen: Pollen from trees, grasses, and weeds causes seasonal allergic rhinitis (hay fever).
• Dust Mites: Tiny bugs in house dust that like warm and humid places.
• Pet Dander: Proteins in the skin, urine, and spit of pets, especially cats and dogs, leading to common indoor allergies.
• Mold: Fungi that create spores in the air, causing allergic reactions, especially in wet conditions.
• Insect Stings: Venom from stinging insects like bees, wasps, and hornets can trigger serious allergic reactions in some people.
• Food Allergies: Some foods often cause allergies. Reactions can happen quickly or take time. Foods like peanuts, shellfish, eggs, and milk commonly cause issues. The immune system reacts to proteins in these foods, leading to symptoms from mild hives to dangerous anaphylaxis.
• Chemical Sensitivities: Some people have allergies to chemicals in perfumes, cleaning supplies, medicines, and others. Reactions can cause skin issues, worsen asthma, or lead to different symptoms.
• Infections and Immune System Issues: Sometimes, infections or exposure to germs as babies may lead to allergies. The hygiene hypothesis says that less exposure to germs early on can make allergies more likely as the immune system overreacts to safe substances.
• Climate and Geography: Some areas have more allergens due to climate that supports mold, pollen, or dust mites. People in cities may have a higher risk because of pollution, which can worsen allergies.

Symptoms

Symptoms of allergies differ based on the allergen type and how the person’s immune system reacts. These can range from can lead to mild discomfort or severe reactions that can be life-threatening. Common symptoms include:

1. Respiratory Symptoms:

• Sneezing: Common in seasonal allergies, mainly because of pollen.
• Runny or Stuffy Nose: This is known as allergic rhinitis or hay fever, occurring when allergens irritate the nose.
• Coughing: A cough may appear due to airway inflammation
• Wheezing and Shortness of Breath: Signs of allergic asthma, which happens when allergens inflame the airways, hindering breathing.

2. Skin Reactions:

• Hives (Urticaria): Red, raised, itchy welts on the skin, often from an allergy to food, drugs, or insect bites.
• Eczema (Atopic Dermatitis): A long-lasting skin condition linked to allergies, causing dry, itchy, red skin patches.
• Angioedema: Swelling under the skin, commonly around the eyes and lips, reacting to allergens.

3. Gastrointestinal Symptoms:

• Nausea and Vomiting: Common in food allergies, especially from nuts, shellfish, and dairy.
• Diarrhea: May occur with food allergies or sensitivities.

4. Anaphylaxis:

A serious allergic reaction that can happen quickly after exposure to allergens, such as food, insect stings, or medications. Symptoms can include breathing issues, throat swelling, low blood pressure, dizziness, and fainting. Anaphylaxis is a medical emergency requiring an epinephrine injection to counteract the reaction.

Risk Factors

Some factors enhance the chance of developing allergies, including:

• Family History: A family background of allergies, asthma, or eczema raises the risk of allergies.
• Age: Allergies can start in childhood but can also appear in adults.
• Allergen Exposure: Early and frequent exposure to certain allergens can elevate the risk of allergies. For example, exposure to pet fur or certain foods may trigger allergies in those genetically likely to develop them.
• Environmental Pollution: Pollution, especially in cities, can worsen existing allergies or lead to new allergic diseases.
• Gender: Boys are more prone to allergies in childhood, but adult women tend to have a higher allergy prevalence.
• Pre-existing Conditions: Issues like asthma and eczema increase the risk of having other allergies. For instance, people with hay fever often develop asthma.

Differential Diagnosis

Allergy symptoms can look similar to other conditions, making it crucial to tell allergies apart from other disorders with like symptoms. Common alternative diagnoses include:

• Infections: Respiratory infections like the common cold or flu can mimic allergic rhinitis or asthma symptoms, usually with fever and fatigue present, which are not found in allergies.
• Non-Allergic Rhinitis: Similar to allergic rhinitis but triggered by irritants like smoke or weather changes and not allergens.
• Asthma: Shares symptoms like wheezing and shortness of breath with allergic asthma, but other asthma types may be triggered by exercise or cold air, not allergens.
• Food Intolerance: Conditions like lactose intolerance can cause bloating, diarrhea, and stomach cramps, resembling food allergy symptoms, but they are distinct in nature. Do not include the immune system and are not serious like food allergies.
• Eczema: Eczema is often tied to allergies but can come from other things like stress, dry skin, or irritants. It is key to tell apart allergic eczema from other types of dermatitis for treatment purposes.

Investigation:

Finding out about allergies usually needs a mix of medical history, physical checks, and tests:

• Skin Prick Test (SPT): This is a common way to find out about environmental allergies. A little bit of allergen is put on the skin, and a needle pricks lightly. If allergic, a bump appears at the spot.
• Blood Tests: Some tests, like the ImmunoCAP test, check IgE antibodies in the blood. High levels mean an allergy to certain things.
• Patch Testing: This is used for allergic contact dermatitis. Small patches with allergens go on the skin for 48 hours to see if a reaction happens.
• Elimination Diet: For food allergies, removing suspected foods from the diet then slowly adding them back can help find triggers.
• Spirometry and Peak Flow Measurement: These tests show lung function and can help identify allergic asthma by checking airway function.

Treatment

Treating allergies is about avoiding allergens, managing symptoms, and sometimes changing how the immune system reacts to them. Common treatments include:

1. Avoidance of Allergens:

The main step in allergy management is to spot and avoid triggers, like certain foods, staying inside during high pollen times, using special bedding, or limiting pet exposure.

2. Medications:

• Antihistamines: These drugs block histamine effects, a chemical that causes symptoms like itching and sneezing. They can be bought over-the-counter or by prescription.
• Corticosteroids: Nasal sprays, inhalers, and oral corticosteroids lower inflammation from allergic reactions. They work well for allergic rhinitis and asthma.
• Decongestants: These medications can relieve nasal stuffiness and reduce swelling in airways.
• Leukotriene Modifiers: These drugs help manage allergic asthma by blocking leukotrienes that cause allergic responses.
• Immunotherapy (Allergy Shots): This method gives small amounts of allergens over time to help the immune system get used to them. It can be a good long-term option for certain allergies like pollen, dust mites, and insect stings.
• Epinephrine: For serious allergic reactions (anaphylaxis), an epinephrine injection helps quickly reverse symptoms and stabilize the person. Those with severe allergies often carry an epinephrine auto-injector.
• Biologic Treatments: New biologic drugs like omalizumab target the immune system specifically and treat severe asthma and chronic hives.

Conclusion

Allergies are common and occur from abnormal responses to harmless substances. Symptoms vary from mild to severe and can impact quality of life.

While there is no cure for allergies, managing them well with avoidance, medications, and immunotherapy can control symptoms and avoid problems.

Ongoing research into what causes allergies and new treatments gives hope for better care for those with allergic diseases.