Allergies

Allergies are very common, affecting about 1 in 3 New Zealanders at some time in their lives.

An allergy occurs when a person’s immune system over-reacts to substances called allergens in the environment. Common allergens include house dust mites, grasses, pollen, pets, foods, some medications, insect stings, latex and moulds. Symptoms range from mild hayfever (runny nose and itchy eyes) to potentially life-threatening, or anaphylactic, reactions.

Food allergies have been on the rise in recent decades, having increased by 50% just between 1997 and 2011.

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Key points:

  1. Allergies are common, however with treatment most people can manage their allergies with minimal problems.
  2. Children have more allergies than adults. As our immune system matures, some allergies disappear.
  3. Allergies occur when your immune system treats an allergen as an invader and begins to create antibodies against it.
  4. The symptoms of allergic reactions range from mild to moderate, to severe and life-threatening (anaphylaxis) See below about what to do in an emergency.
  5. The best way to prevent symptoms is to avoid what triggers the allergy. Talk with your healthcare team to find out what other treatments will help such as nasal sprays, antihistamine tablets and eye drops.

In an emergency

A very severe allergy can cause an anaphylactic reaction, where the person can become very flushed, break out in a rash, have difficulty breathing, suffer a severe drop in blood pressure, and eventually lose consciousness.

This is a life-threatening situation and needs urgent medical attention – call 111 for an ambulance and tell a member of the emergency services what is happening so they can bring the appropriate treatment.

Causes

What is an allergic reaction?

When you have an allergy, your immune system overreacts to a substance that, to most people, is harmless. Your body’s immune system treats the substance (known as an allergen or trigger) as an invader. To defend itself against the allergen, your body produces antibodies called immunoglobulin E (IgE). These antibodies cause certain cells in the body to release chemicals (including histamine) into the bloodstream in an attempt to fight off the invader.

The release of these chemicals causes an allergic reaction. Symptoms vary according to the part of the body affected, but can include sneezing, watery eyes, itch, rash, and raised weals on the skin. Extreme allergic reaction can be life-threatening (anaphylaxis) and needs immediate treatment.

Who gets allergies?

While you do not inherit an allergy directly, you may inherit a tendency to be allergic. This tendency is called being atopic. Allergies start only if you are then exposed to an allergen.

Once you develop a sensitivity to an allergen, an allergic response is set off every time you are exposed to the allergens that affect you. Allergies are often a part of the cause of conditions such as hayfever, eczema and asthma.

Common allergensundefined

A very common indoor environmental allergen is the dust mite or, to be more precise, its droppings. Other common allergens include:

  • pollen, particularly from grass, trees and weeds
  • animal dander (skin, scales or flakes from animals)
  • metals such as nickel in watch-bands, earrings or belt buckles
  • latex in rubber products
  • some moulds
  • insect bites and stings.

A number of foods can also cause allergies, the most common are peanuts, dairy, eggs and seafood. True food allergies are not common and most reactions to food are more likely to be food intolerance rather than an allergic reaction that involves the body's immune system.

Cigarette smoke is often considered a cause but it is actually an irritant rather than an allergen. That means it does not cause the allergy, but makes an existing allergy worse.

Symptoms & diagnosis

Symptoms depend on which part of the body is affected.

  • Hayfever (also known as seasonal allergic rhinitis) affects the eyes and nose, causing sneezing, a runny nose, watery, itchy eyes, irritated and itchy throat and, sometimes, a stuffy, blocked nose.
  • Allergic contact dermatitis (a condition which is caused by the skin coming into contact with an allergen, such as nickel) shows as red, scaly skin that itches.
  • Allergies to some foods, bites or stings can cause urticaria (itchy blisters and weals, which are raised red, itchy patches on the skin).

Tips: There are many causes and symptoms of allergy, so if you think you have an allergy, ask your doctor for advice. See above for severe symptoms and what to do.

Diagnosing allergies

It's important to talk to your doctor if you think you or your child may have an allergy to something. They might suggest tests such as a skin prick test or a blood test (known as a RAST - a radioallergosorbent test).

Skin tests

  • A needle is pricked into the skin through a drop of the suspected allergen, usually on the skin of the person's inner forearm or back.
  • The size of the weal on the skin indicates how strongly you are allergic to a particular allergen.
  • As many as 30 allergens can be tested at the same time to help identify the particular substances to which you are allergic.

Treatment

The most important part of managing allergies is to avoid the allergens if possible. Allergy symptoms also have specific treatments, including medication and self-help practices. The most common medications used for allergies are antihistamines.

Antihistamines

  • are medicines that reduce or block histamines, the substance released by our bodies in response to allergens
  • are usually well-tolerated and work well
  • can be bought from pharmacies or prescribed by your doctor.

Other medications for allergy include:

  • decongestant nasal sprays to relieve a stuffy nose
  • emollient or corticosteroid creams to help soothe inflamed skin

Talk with your doctor or pharmacist about the right medicines for your particular symptoms.

Immunotherapy

Another treatment for some allergies is immunotherapy (desensitisation or hypo-sensitisation). This involves a series of injections that gradually increase the exposure to an allergen and stimulate the immune system to develop a resistance to the allergen. 

It can work very well, eg, insect venoms, such as bee or wasp stings, and can also be helpful for reducing allergic rhinitis and asthma symptoms.

Immunotherapy take time and commitment - about 3 years to complete weekly, then monthly injections (for subcutaneous immunotherapy) or daily then regular drops under the tongue for sublingual immunotherapy. It may be useful for peanut allergies in children under close medical supervision.

Self care

People who are at risk of life-threatening allergic reactions need to carry adrenaline with them at all times and be trained in the correct use of an adrenaline auto-injector (eg, EpiPen, Anapen). For children with allergies, parents or caregivers should also be familiar with how to use the adrenaline auto-injector device. Partners of adults should also be familiar with these devices.

Wearing a medical bracelet stating what you are allergic to can be very helpful for doctors and other health professionals.

Tip: Always remind your doctor or pharmacist of your allergies before starting any new treatment, including complementary/herbal medicines.

Allergic reaction action plan

Allergic reactions can cause a variety of symptoms and range from mild to moderate reactions, to severe and life-threatening (anaphylaxis). Having an action plan (such as those listed below) filled out by your doctor gives you a symptom and treatment guide to follow. Here are two plans from the Australasian Society of Clinical Immunology and Allergy (ASCIA).

It is important that you and your family are able to recognise the signs of an allergic reaction and anaphylaxis and know what to do in an emergency.

Prevention

To minimise allergies, it's important to identify the substances that trigger your allergy and try to avoid them. Here are some tactics to avoid some common allergens and help minimise allergy symptoms.

Dust mites

You can never get rid of all the dust mites in your house, but these measures can help reduce their numbers:

  • If possible, replace wall-to-wall carpets with hard flooring such as floorboards.
  • Clean non-carpeted floors with a wet or electrostatic mop rather than using a vacuum cleaner.
  • Clean carpets 2-3 times each week with a vacuum cleaner that has a suitable filter.
  • Dust surfaces with a damp or electrostatic cloth 2-3 times weekly.
  • Remove fluffy, stuffed toys from your child's bedroom or wash them weekly in hot water (putting soft toys in the freezer overnight kills mites but does not remove allergen).
  • Remove soft, upholstered furniture from the bedroom.
  • Select furniture that is upholstered in vinyl or leather rather than cloth.
  • Ensure good ventilation throughout your house to avoid moist air build-up. If practical, try to sleep with windows open to reduce the amount of moisture in the bedroom from breathing.

Pollen

  • keep the garden free of highly allergenic plants
  • try to stay indoors at times when the pollen count is at its highest, eg, the early evening
  • get someone else to mow your lawn
  • close your bedroom windows at night to prevent pollen entering
  • wear wrap-around sunglasses to avoid pollen getting into your eyes
  • have a shower and wash your hair at night to wash away pollen you may have 'collected' during the day.

Animal dander

Don't keep pets, or at the very least, keep them outside.

Skin allergies

Avoid strong soaps, perfumes and household cleansing products that may irritate sensitive skin.

Insect bites and stings

  • make sure you wear footwear outdoors
  • cover your limbs
  • don't make sudden moves when bees or wasps are around
  • avoid strong perfume as it can attract insects
  • take care in the garden – wear gloves when gardening
  • use insect repellant.

Food allergies: 

If you have food allergies, know what they are and avoid those foods, taking care to maintain a balanced diet. A consultation with a nutritionist or dietitian can be very helpful.

Learn more

A-Z Allergies Allergy NZ
Allergy FAQs  Allergy NZ
Allergy specialists in NZ Allergy NZ
Food allergy myth buster NHS choices
How to use nasal sprays FamilyDoctor.org
Allergies factsheet in multiple languages Health info translations

References

  1. Calderon MA, Alves B, Jacobson M, Hurwitz B, Sheikh A, Durham S. Allergen injection immunotherapy for seasonal allergic rhinitis. Cochrane Database of Systematic Reviews 2007, Issue 1. Art. No.: CD001936. DOI: 10.1002/14651858.CD001936.pub2.
  2. Assessing the efficacy of immunotherapy for desensitisation of peanut allergy in childrenThe Lancet, Volume 383, Issue 9925, Pages 1297 - 1304, 12 April 2014. doi:10.1016/S0140-6736(13)62301-6
  3. Personal action plans for allergies. Produced by the Australasian Society of Clinical Immunology and Allergy (ASCIA)
Credits: Health Navigator, May 2014. Reviewed By: Editorial team Last reviewed: 07 Mar 2015