Overview
Allergy is the immune system's overreaction to a harmless substance such as pollen, animal dander, an insect sting, or food. The body produces antibodies against these substances (allergens), leading to symptoms such as skin rashes, sneezing, itching, and shortness of breath.
About 1 in 5 people lives with an allergic disease. Allergies can range from mild discomfort to life-threatening anaphylaxis.
Symptoms
Symptoms vary depending on the type of allergen.
Hay fever (allergic rhinitis):
- Sneezing
- Runny or stuffy nose
- Itchy, watery eyes
- Itchy palate
Food allergy:
- Itching around the mouth
- Swelling of lips, face, tongue
- Hives (urticaria)
- Abdominal pain, vomiting, diarrhea
- Anaphylaxis
Insect sting allergy:
- Swelling at the sting site
- Generalized itching, hives
- Shortness of breath
- Anaphylaxis
Drug allergy:
- Hives, itching
- Facial swelling
- Wheezing, shortness of breath
- Anaphylaxis
Atopic dermatitis:
- Itchy, dry skin
- Scaling, redness
Anaphylaxis (Life-Threatening)
Some allergies can lead to a body-wide emergency called anaphylaxis:
- Loss of consciousness
- Drop in blood pressure
- Severe shortness of breath
- Rapid, weak pulse
- Skin rash, nausea, vomiting
Call emergency services immediately in case of anaphylaxis.
Causes
Common allergens:
- Airborne: Pollen, dust mites, mold, animal dander
- Foods: Eggs, milk, peanuts, tree nuts, fish, shellfish, soy, wheat
- Insect stings: Bee, wasp
- Medications: Antibiotics, especially penicillin
- Latex
- Contact allergens: Nickel, cosmetics, detergents
Risk Factors
- Family history (strongest)
- Childhood
- Asthma or other allergic disease
- Growing up in highly hygienic environments ("hygiene hypothesis")
Complications
- Anaphylaxis
- Asthma attacks
- Sinusitis, middle ear infection
- Skin infections (from scratching)
- Decreased quality of life
- Sleep disturbances
When to See a Doctor
- If symptoms do not improve with over-the-counter medications
- If you cannot identify the trigger
- If side effects develop
- Call emergency services for signs of anaphylaxis
Diagnosis and Treatment
Diagnosis:
- Detailed history
- Skin prick test
- Blood test (specific IgE)
- Provocation (challenge) test
Treatment:
- Avoidance of allergens (most effective)
- Antihistamines: Cetirizine, loratadine, fexofenadine
- Nasal corticosteroids: Mometasone, fluticasone
- Decongestants: For short-term use only
- Leukotriene receptor antagonists: Montelukast
- Epinephrine auto-injector: Prescribed for those at risk of anaphylaxis
- Immunotherapy (allergy shots): Long-term lasting solution
Prevention
- Avoid triggers
- Wash bedding in hot water (for dust mites)
- Keep windows closed during pollen season
- Use HEPA air purifiers
- Avoid pet dander
- Read food labels carefully
- Wear an allergy bracelet (for severe allergies)
- Always carry your epinephrine auto-injector