ALLERGY
Last Updated : 12/7/2010
Dr. Ira Shah
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What is an allergy?
Allergy is a condition that arises when the body's immunity starts reacting to common substances such as food, drugs and even dust, pollen, animal dander leading to reactions in the body. These substances are known as allergens and may be inhaled, swallowed or can come in body contact through skin.

What are the types of allergies?
Allergies are seen in form of watering of eyes (allergic conjunctivitis) running nose (allergic rhinitis), breathlessness and cough (asthma), skin rashes -wheals and urticaria (allergic dermatitis) and diarrhea (colitis).

Asthma: asthma is a condition that makes breathing out difficult. It affects the air passages in the lungs. This may be caused from pollen, dust, domestic pets, fumes, etc.
Hay fever: This is an uncomfortable reaction to pollen which causes a runny nose, swollen, itchy eyes and other symptoms resembling a head cold.
Skin allergies: It leads to skin rash, eczema. Causes may be plants, domestic pets, foods, drugs, household chemicals, cleaners, etc.
Intestinal allergies may result in abdominal pain/cramps, diarrhea and vomiting. Causative agents of such allergies include food substances, drugs, etc.
Anaphylactic Shock: It is a life threatening allergic reaction that has a wide spread body reaction. It leads to widespread body rash, swelling of the face and neck, breathlessness, anxiety, itching, tightness in the chest, feeling of impending doom, a fast pulse and finally unconsciousness. Anaphylaxis is an emergency and requires immediate action. Call for an ambulance and help the victim rest in the most comfortable sitting position. If the casualty becomes unconscious, check whether resuscitation should be given and treat as appropriate.

Are allergies contagious?
Allergies are not contagious as they are due to aberration in the body's immune system. Hence they cannot be transmitted from one person to the other.

Are allergies hereditary?
Heredity can play some role in allergies. If one parent has an allergic disease, chance of a child developing allergies is 25% and if both parents have allergies, then chances of a child developing allergies is 50%. However, allergies may not be present at birth and can develop at any age.

Why do only few people develop allergies?
This is due to a unique immune system in every individual. When the body comes in contact with an allergen for the first time, the immune system considers it harmful and forms antibodies against it. When the body comes in repeat contact with the allergens, then more antibodies especially an antibody called as IgE is formed that leads to various reactions. IgE releases chemical called histamine that causes swelling, redness, inflammation in organs such as nose, eye, skin, lungs leading to symptoms.

Which are the common substances that lead to allergies?
Smoke, dust, pollen, chemicals, fungi, nuts, beans, potatoes, carrots, lobsters, crabs, shrimps, milk, plastic, drugs such as penicillin and insect bites can lead to allergies in an individual who is prone to allergies.

Why do some individuals get allergies in particular season?
Some patients have allergies throughout the year (perennial allergies) as seen with dust mites which may be present in carpets and mattresses or some may get symptoms only with particular season as seen with allergies to pollen.

Can allergies be life threatening?
A severe reaction to a drug may lead to anaphylaxis - a condition that may be fatal. Asthma if untreated can also be dangerous.

How can I determine to which substance I am allergic?
Many substances can trigger an allergic reaction. To determine which substance is triggering the allergy, skin test using tiny amounts of commonly troublesome allergens is done.

Skin Prick Test:
A tiny amount of allergen is lightly pricked into skin. If you are allergic to that substance, the spot where the allergen entered will swell, itch a bit and form a hive within 15 minutes.

Other test done is RAST test. Skin tests are usually avoided in children less than 8 years of age.

What is the treatment of allergies?
Treatment consists of avoiding the allergen (if one knows the substance causing allergies). Drugs that counter the effects of histamine i.e. anti-histamines are prescribed whenever there is an allergic reaction. However these anti-histaminics may cause drowsiness and should be taken under a doctor's supervision. Other drugs used are steroids in form of nasal spray for allergic rhinitis or eye drops for allergic conjunctivitis and inhaler for asthma. Steroids are used for prevention of an allergic attack and are given for a long time at a minimal dose to keep the patient symptom free.

In few patients (adolescents and adults), another therapy called as immunotherapy may be tried. Immunotherapy is a preventive treatment for allergic reactions to substances such as grass, pollen, house dust mites, wasp and bee venom. It involves giving gradually increasing doses of the substance to which the person is allergic. The gradual increases of the allergen causes the immune system to become less sensitive to the substance probably by producing a blocking antibody.

In which conditions can immunotherapy be used?
Immunotherapy is used in allergic rhinitis, allergies to drugs,asthma and insect sting allergy. It is of no use in skin allergies. Immunotherapy is usually given for few months to 2-3 years and benefits are seen after 6 months to 1 year.

How is immunotherapy given?
Immunotherapy is given as injection into the skin starting with low doses of allergen once or twice a week following which it is gradually increased. After 6 months to 1 year, maintenance injections are given once in 2 weeks to maintain benefit.

Can allergy be cured?
No, some individuals may outgrow allergies but it cannot be cured. Thus prevention remains the mainstay of treatment.

Tips for preventing exposure to allergens:
- Clean all filters, air conditioner filters and duct filters every 3-4 months at home, workplace and in car.
- Replace Venetian blinds with roll down shades.
- Avoid keeping pets.
- Use a damp cloth to dust.
- Avoid a mould - preventive agent to paint and choose a mould-resistant wall paper paste.
- Repair any plumbing leaks to reduce mould formation.
- Use food products, cosmetics and perfumes with out artificial flavoring or preservative.



Contributor Information and Disclosures

Dr. Ira Shah
Consultant Pediatrician, B.J.Wadia Hospital for Children, Mumbai, India


First Created : 2/13/2001

References

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