I am considering allergen immunotherapy for my hay fever. What should I know?

Allergic rhinitis, commonly known as hay fever, is a common allergic disorder affecting up to one in five Australians. Symptoms include itchy nose and eyes, excessive sneezing or a clear runny nose, and nasal congestion.

When severe or untreated, hay fever can affect your quality of life, leading to poor sleep, learning difficulties, and difficulty concentrating at school or work.

People with hay fever usually use over-the-counter antihistamines as needed. For recurring or frequent symptoms, corticosteroid nasal sprays are easily available over-the-counter preventative medications and are most effective when used regularly.

However, if you continue to have severe and troubling symptoms, you might consider allergen immunotherapy, also known as allergen desensitization.

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Remind me, what happens when you have hay fever?

Hay fever triggers an exaggerated immune response against otherwise harmless airborne allergens such as grass pollen, dust mites or animal dander. These can end up on the lining of the nose and eyes, causing irritation.

When it encounters these allergens in the form of foreign molecules, the immune system generates proteins, called antibodies. These antibodies are able to accurately recognize that particular molecule as foreign.

In people with hay fever, a special type of antibody, called IgE, is generated. These allergen-specific IgE antibodies then “prime” or prepare the cells in the lining of the nose and eyes to recognize and trigger allergic reactions when exposed to these allergens.

When “primed” cells come into contact with the allergen, they release stored molecules, such as histamine. Histamine acts on nearby cells to trigger symptoms such as itching, sneezing, and runny nose.

Over time, continued stimulation by the allergen will trigger a chronic response. This leads to nasal congestion and swelling of the tissues of the nasal or ocular lining.

For some people, nasal sprays do not provide enough relief.

How does allergen immunotherapy work?

The first step is to ask your GP for a referral to an allergist or clinical immunologist to discuss the best treatment for you.

Your allergist or clinical immunologist will start by identifying your triggers. This can be done through skin tests during your visit to the allergy clinic or through blood tests that detect and measure the proteins (antibodies) that underlie the allergic response.

Allergen immunotherapy attenuates the exaggerated response to a specific allergen. It does this by developing cells and antibodies that block rather than activate the immune response against a particular allergen.

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How is it administered?

Allergen immunotherapy is given either by injections under the skin (subcutaneous) or by drops, tablets or pills placed under the tongue (sublingual).

Treatment is initiated by a clinic allergist. Injection allergen immunotherapy can then be given regularly by your GP, usually monthly, while sublingual allergen immunotherapy is taken daily at home.

Patients often ask which treatment is best. Research indicates that both are effective strategies for minimizing allergy symptoms. For an individual, the choice should depend on a number of factors such as asthma, expected tolerance and most importantly time constraints (eg how long it takes to see a GP).

While allergen immunotherapy for children can begin as young as five years old, parents should discuss the best treatment for their child with the allergist. Some children may not tolerate regular injections, while others are unable to hold the tablet under their tongue.

How much does it cost?

The cost varies by product as allergen immunotherapy products are not subsidized under PBS.

Sublingual allergen immunotherapy products cost around AU$120-150 per month.

The injection costs about 600 to 1200 Australian dollars per year (about 50 to 100 Australian dollars per month).

How long does it take to work?

The allergist will determine the best time to start allergen immunotherapy, as some products would be best to start before spring (eg grass pollen immunotherapy).

Effective allergen immunotherapy should minimize allergic symptoms after further exposure to the allergen. However, this immune “reset” does not have an immediate effect. Patients on allergen immunotherapy usually do not notice an improvement in symptoms until after six to 12 months.

person with red eyes
Hay fever is an allergic reaction causing symptoms such as itchy eyes.
Erik McLean

Patients undergoing treatment should expect improvement in symptoms within the first year, although there may be continued gradual improvements over subsequent years of treatment.

Allergen immunotherapy may also help reduce asthma flare-ups in people diagnosed with the disease who also have hay fever. It is particularly effective in preventing asthma flare-ups caused by turbulent weather storms, also known as thunderstorm asthma.

Allergen immunotherapy may also reduce the risk of children with hay fever developing asthma.

What are the side effects?

Allergen immunotherapy by sublingual route or injections can usually cause local allergic symptoms such as itching, tingling of the tongue/mouth or localized redness or pain at the injection site.

Significant side effects from both routes of allergen immunotherapy are very rare and may include a severe allergic reaction, particularly if you have asthma. Asthma patients should only start allergen immunotherapy if and when their asthma is well controlled.

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How long do the improvements last?

For effective allergen immunotherapy, patients should receive gradual and regular administration of the trigger allergen(s) for at least three years.

The clinical benefits of allergen immunotherapy are not indefinite, but allergen immunotherapy given regularly for three to five years will help prolong the sustained response for at least two to three years after discontinuation.

During this period, patients should have at least one annual check-up with their specialist to ensure that the treatment is working and that there are no side effect issues.

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