Allergy
An immune system reaction to substances that are normally harmless to most people
Quick Facts
- Type: Immune System Disorder
- ICD-10: T78.4
- Prevalence: ~25% of population
- Onset: Any age
Overview
An allergy is an immune system response to a foreign substance (allergen) that's not typically harmful to your body. These foreign substances can include certain foods, pollen, animal dander, medications, or insect stings. When you have an allergy, your immune system makes antibodies that identify a particular allergen as harmful, even though it isn't. This leads to inflammation of your skin, sinuses, airways, or digestive system.
Allergies are extremely common, affecting approximately 25% of the population in developed countries. They can develop at any age, though many allergies first appear in childhood. Some people outgrow their allergies, while others develop new ones throughout their lives. The severity of allergic reactions can range from mild symptoms like sneezing and itching to life-threatening reactions such as anaphylaxis.
There are several types of allergies, including respiratory allergies (like hay fever), food allergies, drug allergies, and contact allergies. Understanding your specific allergens and how to manage them is crucial for maintaining quality of life and preventing serious reactions. With proper identification, avoidance strategies, and treatment, most people with allergies can live normal, active lives.
Symptoms
Allergy symptoms depend on the type of allergen and how it enters your body. Symptoms can range from mild to severe and may appear immediately or take hours to develop.
Common Symptoms
Respiratory Allergy Symptoms
- Sneezing and runny nose
- Itchy, watery eyes
- Nasal congestion
- Persistent cough
- Postnasal drip
- Throat clearing
- Dark circles under eyes ("allergic shiners")
Food Allergy Symptoms
- Nausea and vomiting
- Diarrhea or stomach cramps
- Lip or tongue swelling
- Tingling in mouth or throat
- Skin rashes or hives
- Difficulty swallowing
Contact Allergy Symptoms
- Red, inflamed skin
- Blisters or oozing lesions
- Dry, scaly patches
- Burning or stinging sensation
- Localized swelling
Severe Allergic Reaction (Anaphylaxis)
Seek emergency medical care immediately if you experience:
- Difficulty breathing or wheezing
- Rapid, weak pulse
- Dizziness or fainting
- Widespread rash or hives
- Severe swelling of face, lips, or throat
- Nausea, vomiting, or diarrhea
- Loss of consciousness
Causes
Allergies occur when your immune system mistakenly identifies a harmless substance as a threat and produces antibodies to fight it. This overreaction can cause various symptoms throughout your body.
How Allergies Develop
The allergic process involves several steps:
- Initial exposure: First contact with allergen
- Sensitization: Immune system creates specific antibodies (IgE)
- Re-exposure: Subsequent contact with allergen
- Reaction: Antibodies trigger release of histamine and other chemicals
- Symptoms: Resulting inflammation and other allergic symptoms
Common Allergens
Environmental Allergens
- Pollen: Tree, grass, and weed pollens
- Dust mites: Microscopic creatures in house dust
- Mold spores: Indoor and outdoor fungi
- Animal dander: Skin flakes from pets
- Cockroach allergens: Particles from cockroach waste
Food Allergens
- Most common: Milk, eggs, peanuts, tree nuts, wheat, soy, fish, shellfish
- Fruits: Berries, citrus fruits, stone fruits
- Vegetables: Tomatoes, celery, certain beans
- Additives: Food coloring, preservatives, sulfites
Drug Allergens
- Antibiotics: Penicillin, sulfonamides, others
- Pain relievers: Aspirin, NSAIDs
- Anesthetics: Local and general anesthetics
- Other medications: Insulin, vaccines, chemotherapy drugs
Contact Allergens
- Metals: Nickel, chromium, cobalt
- Plants: Poison ivy, poison oak, poison sumac
- Chemicals: Fragrances, preservatives, rubber compounds
- Cosmetics: Hair dyes, nail polish, makeup
Insect Allergens
- Bee, wasp, hornet, yellow jacket stings
- Fire ant bites
- Mosquito and other insect bites
Factors Influencing Allergy Development
- Genetics: Family history of allergies
- Environment: Exposure patterns and timing
- Age: Early childhood exposures
- Immune system status: Overall health and function
- Other medical conditions: Asthma, eczema
Risk Factors
Several factors can increase your likelihood of developing allergies:
Genetic Factors
- Family history: Having parents or siblings with allergies
- Inherited tendency: Genetic predisposition to atopy
- Specific genes: Variations in immune system genes
- Ethnicity: Some allergies more common in certain populations
Age-Related Factors
- Early childhood: Higher risk for food allergies
- School age: Environmental allergies often develop
- Adolescence: Some allergies may worsen
- Adulthood: New allergies can still develop
Environmental Factors
- Early exposure: Introduction to allergens in infancy
- Pollution: Air quality and chemical exposure
- Climate: Humidity, temperature variations
- Urban vs. rural: Different exposure patterns
- Hygiene hypothesis: Reduced early-life pathogen exposure
Medical Conditions
- Asthma: Often occurs with allergies
- Eczema (atopic dermatitis): Skin condition linked to allergies
- Other allergies: Having one allergy increases risk for others
- Immune deficiencies: Compromised immune function
Lifestyle Factors
- Diet: Early feeding patterns, food diversity
- Smoking exposure: Firsthand or secondhand smoke
- Stress: Chronic stress affecting immune function
- Medications: Certain drugs affecting immune response
- Infections: Viral infections during critical periods
Occupational Factors
- Chemical exposure: Industrial chemicals and solvents
- Biological materials: Animal proteins, plant materials
- Healthcare workers: Latex, medication exposure
- Agricultural workers: Pesticides, plant allergens
Gender and Hormonal Factors
- Childhood: Boys more likely to have allergies
- Adulthood: Women more likely to develop new allergies
- Hormonal changes: Pregnancy, menopause affecting symptoms
- Hormonal medications: Birth control pills, hormone therapy
Diagnosis
Diagnosing allergies involves a combination of medical history, physical examination, and specialized testing to identify specific allergens.
Medical History
- Symptom patterns: When, where, and how symptoms occur
- Family history: Allergies in relatives
- Environmental factors: Home, work, and lifestyle exposures
- Previous reactions: Detailed description of past episodes
- Medications: Current and past medication use
- Triggers: Suspected allergens or situations
Physical Examination
- Skin examination: Looking for rashes, hives, or eczema
- Nasal examination: Checking for inflammation or polyps
- Eye examination: Signs of allergic conjunctivitis
- Lung examination: Listening for wheezing or other sounds
- General assessment: Overall health and signs of systemic reaction
Allergy Testing
Skin Tests
- Skin prick test: Small amounts of allergens placed on skin
- Intradermal test: Allergen injected under skin
- Patch test: For contact allergies, patches applied for 48 hours
- Results: Positive reactions show as raised, red areas
Blood Tests
- Specific IgE tests: Measure antibodies to specific allergens
- Total IgE level: Overall allergic tendency
- Component testing: Identifies specific protein allergens
- Advantages: Safe for severe allergies, not affected by medications
Challenge Tests
- Food challenge: Eating suspected food under medical supervision
- Drug challenge: Taking suspected medication in controlled setting
- Exercise challenge: Testing for exercise-induced allergies
- Environmental challenge: Exposure to suspected environmental allergens
Specialized Testing
- Pulmonary function tests: For respiratory allergies
- Nasal smear: Checking for eosinophils
- Elimination diet: Systematic removal and reintroduction of foods
- Environmental monitoring: Measuring allergen levels in environment
Interpretation of Results
- Positive tests: Don't always mean clinical allergy
- Negative tests: Don't rule out all allergies
- Clinical correlation: Results must match symptoms
- Specialist interpretation: Allergist evaluation often needed
Treatment Options
Allergy treatment focuses on avoiding allergens, managing symptoms, and in some cases, reducing sensitivity through immunotherapy. Treatment plans are individualized based on specific allergies and symptom severity.
Allergen Avoidance
The most effective treatment is avoiding known allergens:
- Environmental control: HEPA filters, dust mite covers, humidity control
- Food avoidance: Reading labels, avoiding cross-contamination
- Pet management: Keeping pets out of bedrooms, regular grooming
- Pollen avoidance: Staying indoors during high pollen days
- Chemical avoidance: Using fragrance-free products
Medications
Antihistamines
- Oral antihistamines:
- Loratadine (Claritin): 10mg daily
- Cetirizine (Zyrtec): 10mg daily
- Fexofenadine (Allegra): 180mg daily
- Diphenhydramine (Benadryl): 25-50mg every 6 hours
- Nasal antihistamines:
- Azelastine (Astelin): 2 sprays per nostril twice daily
- Olopatadine (Patanase): 2 sprays per nostril twice daily
- Eye drops:
- Ketotifen (Zaditor): 1 drop in each eye twice daily
- Olopatadine (Pataday): 1 drop in each eye daily
Corticosteroids
- Nasal corticosteroids:
- Fluticasone (Flonase): 2 sprays per nostril daily
- Budesonide (Rhinocort): 1-4 sprays per nostril daily
- Mometasone (Nasonex): 2 sprays per nostril daily
- Topical corticosteroids: For skin allergies
- Oral corticosteroids: For severe reactions (short-term use)
Other Medications
- Decongestants: Pseudoephedrine, phenylephrine
- Leukotriene modifiers: Montelukast (Singulair)
- Mast cell stabilizers: Cromolyn sodium
- Bronchodilators: For allergic asthma
Emergency Treatment
For severe allergic reactions (anaphylaxis):
- Epinephrine auto-injector: EpiPen, Auvi-Q for immediate use
- Emergency medical care: Call 911 immediately
- Secondary medications: Antihistamines, corticosteroids in hospital
- Observation: Monitor for biphasic reactions
Immunotherapy
- Allergy shots (subcutaneous):
- Build-up phase: Increasing doses over 3-6 months
- Maintenance phase: Regular injections for 3-5 years
- Effective for environmental allergies, insect stings
- Sublingual immunotherapy:
- Daily tablets or drops under tongue
- Available for some pollens, dust mites
- Can be done at home after initial dosing
Alternative and Complementary Treatments
- Nasal irrigation: Saline rinses to remove allergens
- Air purification: HEPA filters, air cleaners
- Natural antihistamines: Quercetin, butterbur (limited evidence)
- Acupuncture: May help some people with allergic rhinitis
- Probiotics: May support immune system balance
Prevention
While you can't always prevent allergies from developing, you can reduce exposure to allergens and minimize symptoms:
Environmental Allergy Prevention
- Indoor air quality:
- Use HEPA air purifiers
- Keep humidity below 50%
- Fix water leaks promptly to prevent mold
- Use allergen-proof covers on bedding
- Wash bedding weekly in hot water (130°F/54°C)
- Pollen reduction:
- Keep windows closed during high pollen days
- Use air conditioning with clean filters
- Shower and change clothes after outdoor activities
- Dry clothes indoors during pollen season
Food Allergy Prevention
- Early introduction: Introduce potential allergens to infants appropriately
- Breastfeeding: May reduce allergy risk in high-risk infants
- Label reading: Always check ingredient lists
- Cross-contamination: Prevent contact with allergens during food preparation
- Restaurant precautions: Inform staff about allergies
Contact Allergy Prevention
- Skin protection: Wear gloves when handling potential allergens
- Product selection: Choose fragrance-free, hypoallergenic products
- Patch testing: Test new products on small skin area first
- Jewelry choices: Avoid nickel-containing jewelry
Pet Allergy Management
- Pet-free zones: Keep bedrooms and main living areas pet-free
- Regular grooming: Bathe pets weekly
- Air filtration: Use HEPA filters throughout home
- Cleaning: Vacuum frequently with HEPA filter
General Prevention Strategies
- Stress management: Reduce stress which can worsen allergies
- Healthy lifestyle: Exercise, adequate sleep, good nutrition
- Avoid smoking: Don't smoke and avoid secondhand smoke
- Monitor weather: Check pollen and air quality reports
- Medication compliance: Take preventive medications as prescribed
Travel Considerations
- Research allergens at destination
- Pack sufficient medications
- Carry emergency action plan
- Inform travel companions about allergies
- Consider medical alert jewelry
When to See a Doctor
Knowing when to seek medical care for allergies can help prevent complications and improve your quality of life:
Seek Emergency Medical Care
- Signs of anaphylaxis:
- Difficulty breathing or wheezing
- Swelling of face, lips, tongue, or throat
- Rapid, weak pulse
- Dizziness or fainting
- Severe whole-body reaction
- Loss of consciousness
- Severe asthma attack: Triggered by allergen exposure
- Any reaction: That seems to be getting worse rapidly
Schedule Urgent Appointment
- New severe allergic reaction
- Allergic reaction to new medication
- Persistent symptoms despite treatment
- Signs of secondary infection (fever, pus)
- Inability to function normally due to symptoms
Schedule Routine Appointment
- Suspected new allergies: Want testing and identification
- Poorly controlled symptoms: Current treatment not effective
- Frequent reactions: Recurring allergic episodes
- Medication side effects: Problems with current allergy medications
- Quality of life impact: Allergies affecting daily activities
- Immunotherapy consideration: Interest in allergy shots or tablets
Consider Allergy Specialist Referral
- Complex or multiple allergies
- Severe or life-threatening reactions
- Need for comprehensive allergy testing
- Consideration for immunotherapy
- Occupational or unusual allergies
- Allergies affecting work or school performance
Preparation for Medical Visits
- Symptom diary: Track triggers, timing, and severity
- Medication list: All current and past allergy treatments
- Family history: Allergies in relatives
- Environmental factors: Home, work, and lifestyle exposures
- Questions prepared: Specific concerns and goals for treatment
Frequently Asked Questions
Yes, you can develop new allergies at any age. Adult-onset allergies are common and can occur even if you've never had allergies before. Environmental changes, hormonal shifts, stress, and exposure to new allergens can all trigger the development of allergies in adulthood.
Allergies have a strong genetic component. If one parent has allergies, a child has about a 25-30% chance of developing allergies. If both parents have allergies, the risk increases to 60-70%. However, the specific allergies inherited may be different from those of the parents.
Currently, there's no cure for allergies, but they can be effectively managed. Immunotherapy (allergy shots or tablets) can significantly reduce or eliminate symptoms for some people, and some individuals may outgrow certain allergies, particularly food allergies in children. Most people can achieve good symptom control with proper treatment.
Allergy tests are generally reliable when interpreted by qualified healthcare providers. However, positive test results don't always mean you'll have symptoms when exposed to that allergen. Negative tests usually rule out allergies, but false negatives can occur. Clinical correlation with symptoms is essential for accurate diagnosis.
Most modern allergy medications are safe for long-term use when taken as directed. Non-sedating antihistamines and nasal corticosteroids are generally well-tolerated for extended periods. However, it's important to work with your healthcare provider to monitor effectiveness and any potential side effects.
Yes, stress can worsen allergy symptoms. Stress affects the immune system and can increase inflammation, making you more sensitive to allergens. Managing stress through relaxation techniques, exercise, and adequate sleep can help improve allergy control.
References
- American Academy of Allergy, Asthma & Immunology. Allergy Guidelines and Practice Parameters. AAAAI. 2023.
- World Allergy Organization. Global Guidelines for Allergy Management. WAO. 2023.
- National Institute of Allergy and Infectious Diseases. Guidelines for the Management of Food Allergy. NIAID. 2023.
- European Academy of Allergy and Clinical Immunology. EAACI Guidelines. 2023.
- Sicherer SH, Sampson HA. Food allergy: A review and update on epidemiology, pathogenesis, diagnosis, prevention, and management. J Allergy Clin Immunol. 2023.