Allergies

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 your body to release chemicals such as histamine into your 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 your body affected, but can include sneezing, watery eyes, itching, rash and raised weals (hives) on your skin. Extreme allergic reactions can be life-threatening and needs immediate treatment. This is called anaphylaxis.

While you don’t inherit an allergy directly, you may inherit a tendency to be allergic and develop allergic diseases. This tendency is called being atopic. Allergies start only if you are 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. 

Substances in the environment that can cause an allergic reaction are called allergens. Common allergens include:

• the droppings of house dust mites 
• 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
• household chemicals such as those in hair dyes and detergents
• medicines
• foods such as peanuts, dairy, eggs and seafood.

True food allergies are not common. Most reactions to food are more likely to be food intolerance, which doesn’t involve your body’s immune system. An allergic reaction involves your body's immune system. Read more about the difference between food allergies and food intolerance.

Cigarette smoke is often considered a cause of allergies, but it is actually an irritant rather than an allergen. That means it doesn’t cause an allergy, but makes an existing allergy worse.

Depending on the type of allergens and where allergens enter your body, they can cause different allergic reactions and conditions. These include:

• allergic rhinitis (hay fever)
• allergic contact dermatitis
• allergic conjunctivitis
• asthma
• food allergies
• anaphylaxis (severe allergic reaction).

Symptoms depend on where allergens enter your body and which part of your body is affected. They can range from mild to severe. Typically, symptoms happens within minutes to an hour after you are exposed to a particular allergen.

• Hay fever (also known as  allergic rhinitis) affects your eyes and nose when you inhale allergens. Symptoms include sneezing, runny nose, watery and itchy eyes, irritated and itchy throat and, sometimes, a stuffy, blocked nose.
• Allergic contact dermatitis is a condition caused by your skin coming into contact with an allergen, such as nickel. Symptoms include red, scaly skin that itches.
• Allergies to some foods, insect bites or stings can cause hives (urticaria), which are raised red, itchy patches on your skin, and other symptoms such as nausea or vomiting, swelling around your lips, face and eyes, diarrhoea (runny poo) or sneezing.
• Anaphylaxis is a severe allergic reaction. It can involve your whole body and is a life-threatening condition. It requires immediate life-saving medicine such as adrenaline. Read more about anaphylaxis.

It's important to talk to your doctor if you think you or your child may have an allergy to something. There are many causes of allergies and some symptoms may be due to other conditions.

Your GP or doctor will ask you or your child about allergic symptoms such as a rash or an upset stomach. Other questions may include the following:

• When do your symptoms occur when exposed to a particular allergen?
• How often do your symptoms occur?
• Is there anything that will trigger your symptoms?
• Are there any family members who also have allergies?
• Have you been exposed to new foods, pets or medicines recently?

When symptoms appear soon after you have been exposed to a particular allergen, it is easy to identify which allergen is causing your reaction. However, if the cause is unknown, other diagnostic tests may be needed. This might include a skin prick test or a blood test to test for the presence of an antibody (IgE) that causes an allergic reaction. Your doctor may also refer you or your child to a paediatric clinic or allergy specialist for further tests if the cause is still unclear.

Skin prick tests

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

The most important part of managing allergies is to avoid allergens, if possible. Allergic symptoms also have specific treatments, including medicines and self-help measures. For some allergic conditions such as allergic rhinosinusitis, allergen immunotherapy (AIT) can also help.

Medicines

Medicines are used to treat allergic symptoms, including:

• antihistamines
• steroid tablets
• steroid nasal inhalers or decongestant nasal spray
• medicated or non-medicated eye drops
• emollient or corticosteroid creams
• adrenaline – usually in an autoinjector called EpiPen.

Antihistamines

• Antihistamines are medicines that reduce or block histamines, the substance released by your body in response to allergens.
• They are most commonly used to treat allergic symptoms.
• Antihistamines are usually well tolerated and work well.
• Antihistamines can be bought from pharmacies or prescribed by your doctor.
• Ask your pharmacist/chemist or doctor if you are unsure which one you need.
• Read more about antihistamines.

Steroid tablets

• Steroid tablets can also be used to treat allergic symptoms such as hives and to reduce inflammation.
• A prescription by your doctor is needed.
• Read more about steroid tablets.

Steroid nasal inhalers or decongestant nasal sprays

• These are used to relieve symptoms of hay fever.
• A prescription may be needed for stronger doses of steroids.
• Decongestant nasal sprays can relieve stuffiness or congestion of your nostrils, and can be bought over the counter. However, these medicines are not suitable for long-term use. Ask your pharmacist or doctor if you are unsure whether these are suitable for you.
• Read more about steroid nasal sprays and decongestant nasal sprays.

Medicated or non-medicated eye drops

• Some eye drops may be helpful in some allergic conditions such as allergic conjunctivitis.
• These eye drops can be lubricating eye drops or may contain steroids.
• Ask your doctor or pharmacist about suitable eye drops for you.
• Read more about eye drops.

Emollients and corticosteroid creams

• Emollients or corticosteroid creams can help improve allergic symptoms or conditions that involve your skin, such as hives or eczema.
• Read more about emollients and corticosteroid creams.

Adrenaline

• Adrenaline is used in an emergency to treat anaphylaxis.
• It is usually in the form of an autoinjector, called an EpiPen.
• EpiPens are easy to use and can be given by non-medical people.
• If you have been prescribed an EpiPen, your doctor or pharmacist can teach you how to use it.
• Read more about EpiPen.

Allergen immunotherapy (AIT)

When medicines don’t provide enough relief, an option is immunotherapy. Immunotherapy may also be an option if your symptoms are severe and the allergen is difficult to avoid, eg, in allergic rhinosinusitis or allergic conjunctivitis. 

The aim of immunotherapy is to make you develop tolerance to a particular allergen. It works by changing the way your immune system reacts to allergens. Your doctor will give you an allergen you are allergic to, either under your tongue, through your nose or by an injection. This will be repeated over a period of 3–5 years. 

Not everyone is suitable for immunotherapy. Ask your doctor or an allergy specialist about whether you are suitable for immunotherapy. 

The best way to prevent an allergic reaction is to identify the substances that trigger your allergy and try to avoid them.

Here are some tips to avoid some common allergens and help minimise allergic 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 allergens.
• Remove soft, upholstered furniture from the bedroom.
• Select furniture that is upholstered in vinyl or leather rather than cloth.
• Aim for good ventilation throughout your house to avoid moist air build-up.
• 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

• Keep pets outside, if possible.

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 arms and legs.
• Don't make sudden moves when bees or wasps are around.
• Avoid strong perfume as it can attract insects.
• Wear gloves when gardening.
• Use insect repellant.

Food allergies

If you have food allergies, know what they are and avoid those foods. A consultation with a nutritionist or dietitian can help you work out how to do this and still have a healthy, balanced diet. Ask your doctor for a referral to a dietitian.

Some self-care measures you can do to help manage your allergies include:

Avoid allergies

It is not always practical to avoid the allergens you are allergic to. However, some things you can do include:

• being careful about what you eat if you have food allergies
• avoiding exposure to pets if you have animal allergies
• keeping your home warm and dry if you have mould allergies
• staying indoors and avoiding grassy areas if you have hay fever.

Carry adrenaline

If you are at risk of life-threatening allergic reactions, you need to carry adrenaline with you at all times. You also need to be trained in the correct use of an adrenaline auto-injector, EpiPen.

For children with allergies, parents or caregivers should also be familiar with how to use the EpiPen. Partners of adults should also be familiar with these devices.

Allergic reaction action plan

Allergic reactions can cause a variety of symptoms ranging from mild to moderate reactions, through to severe and life-threatening reactions (anaphylaxis). You and your family/whānau need to be able to recognise the signs of an allergic reaction and anaphylaxis, and know what to do in an emergency.

An allergic reaction action plan is a written document that outlines what to do if you have an allergic reaction. 

Here are two plans from the Australasian Society of Clinical Immunology and Allergy (ASCIA):

• Action plan for anaphylaxis(external link)

Carry your allergy action plan at all times or put your action plan somewhere accessible easily in your home. If you don’t have an action plan, ask your doctor to fill out one with you.

Wear a medical bracelet

Wear a medical bracelet stating what you are allergic to. This can be very helpful for health professionals when treating you.

Remind your healthcare team

Always remind your doctor or pharmacist of your allergies before starting any new treatment, including complementary, over-the-counter and herbal medicines.

Apps reviewed by Healthify 

You may find it useful to look at The Insides Guide - is it dairy free? app.

Allergy New Zealand(external link)(external link) provides information, education and support for people with allergy, parents of children with allergy, teachers or healthcare professionals. 

Apps

Digestive health apps
First aid and emergency apps