What is Allergen Immunotherapy?
Allergen-specific immunotherapy is a potentially disease-modifying therapy that is effective for the treatment of allergic rhinitis/conjunctivitis, allergic asthma and stinging insect hypersensitivity.
Immunotherapy contains a tiny amount of the specific substance or substances that trigger your allergic reactions. These are called allergens. It contains just enough allergens to stimulate your immune system — but not enough to cause a full-blown allergic reaction.
Over time, your doctor increases the dose of allergens. This helps get your body used to the allergens (desensitization). Your immune system builds up a tolerance to the allergens, and your allergy symptoms diminish over time.
Immunotherapy is an effective way of modifying or avoiding disease by influencing the immune system. Immunotherapy help your body get used to allergens, the things that trigger an allergic reaction.
Immunotherapy decrease sensitivity to allergens and often leads to lasting relief of allergy symptoms even after treatment is stopped. This makes it a cost-effective, beneficial treatment approach for many people.
How it benefits the patient?
- The clinical efficacy of allergen immunotherapy is well documented, and it shown to improve symptoms, reduce medications and provide long term benefits even after cessation of therapy.
- Long term benefits > 3 years after discontinuation of therapy.
- Treating children with allergic rhinitis with immunotherapy protect them from development of asthma.
Improvement with allergen immunotherapy does not occur immediately. It usually requires at least 4-5 months before symptoms improve, sometimes longer. If you are having treatment because of spring/summer allergic rhinitis, you will usually see improvement quite clearly in the first season.
It is recommended that allergen immunotherapy is continued for about 3-5 years, to reduce the likelihood that your allergies will return. While undergoing allergen immunotherapy, you can still use your allergy medications and you should continue your asthma medications at the same time in the usual way. It is important to note that allergen immunotherapy should only be initiated by a doctor who is fully trained in allergy.
Why do you need Immunotherapy?
Immunotherapy is a good treatment choice for you if:
- It’s impossible to avoid the things that cause your allergic reactions.
- Allergy medications fail to control your symptoms completely.
- Allergy medications cause bothersome side effects or interactions with other medications you need to take.
- You want to reduce your long-term use of allergy medication.
- You’re allergic to insect stings.
Immunotherapy can be used to control symptoms triggered by:
- Seasonal allergies. If you have seasonal allergic asthma or hay fever symptoms, you may be allergic to pollens released by trees, grasses or weeds.
- Indoor allergens. If you have year-round symptoms, you may be sensitive to indoor allergens, such as dust mites, cockroaches, mould or dander from pets, such as cats or dogs.
- Insect stings. Allergic reactions to insect stings can be triggered by bees, wasps, hornets or yellow jackets.
Allergy shots aren’t available for food allergies or chronic hives (urticaria), andgioedema drug allergy.
How does Immunotherapy Work?
It works like a vaccine. Your body responds to injected amounts of a particular allergen, given in gradually increasing doses, by developing immunity or tolerance to the allergen. There are two phases:
- Build-up phase. This involves receiving injections with increasing amounts of the allergens about one to two times per week. The length of this phase depends upon how often the injections are received, but generally ranges from three to six months.
- Maintenance phase. This begins once the effective dose is reached. The effective maintenance dose depends on your level of allergen sensitivity and your response to the build-up phase. During the maintenance phase, there will be longer periods of time between treatments, ranging from two to four weeks. Your allergist / immunologist will decide what range is best for you.
You may notice a decrease in symptoms during the build-up phase, but it may take as long as 12 months on the maintenance dose to notice an improvement. If allergy shots are successful, maintenance treatment is generally continued for three to five years.
What is Sublingual Immunotherapy?
Sublingual immunotherapy is used by physicians in many countries: it involves putting drops or a tablet of allergen extracts under the tongue to swallow the extract. It allows the body to become tolerant of the allergen by absorbing the allergen through the stomach lining. Today, sublingual immunotherapy can count on more than 60 controlled clinical trials, proving its efficacy and safety profile and leading to its recognition as a viable route by the international guidelines. The treatment is usually taken at home.
Common methods for taking the Allergen extracts:
- Take in the morning on an empty stomach.
- Keep the drops or tablet under the tongue for at least 2 minutes, then swallow.
- Do NOT eat/drink anything for 15 minutes.
- Avoid crunchy cereals as these may cut the tongue and increase the likelihood of mouth irritation from the extracts.
- If you forget to take them in the morning, continue treatment the next morning at the usual dosage.
Side-effects of Sublingual Immunotherapy
Common side effects include irritation, minor swelling or itching inside the mouth, stomach upset/nausea. This can be controlled by temporarily reducing the dose or taking an oral non-sedating antihistamine beforehand. These side effects generally resolve after the first few weeks.
The risk of potentially dangerous side-effects arising from this form of treatment, such as difficulty breathing, is extremely low.
What is Subcutaneous Immunotherapy?
Allergy injections start with a very low dose. A small needle is used which may be uncomfortable, but not very painful. The dose is gradually increased on a regular (usually weekly) basis, until an effective (maintenance) dose is reached. This usually takes three to six months. This dose may vary between patients, depending on the degree of sensitivity.
Once the maintenance dose is reached, injections are administered less often, usually monthly, although still on a regular basis. Immunotherapy injections should always be administered in a medical facility under medical supervision. You should stay at the medical facility for the time recommended by the allergy specialist (30-45 minutes) after the immunotherapy injection has been given.
Side effects of Immunotherapy injections
Some patients develop a localised swelling at the site of the injection. This can be treated with non-sedating oral antihistamines or ice packs and if painful, Paracetamol. If the swelling is significant, your doctor may need to reduce the next dose.
More serious reactions (such as anaphylaxis) are uncommon; however predicting who might have the serious reactions is difficult. Patients are normally advised to:
- Remain in their doctor’s surgery for at least 30 minutes after injection.
- Avoid exercising for at least 3 hours afterwards.
- Avoid some heart and blood pressure medications (e.g. beta blockers such as metoprolol or propranolol). Must be discussed with prescribing doctor.
- Taking a non-sedating oral antihistamine before the injection may reduce the risk of side effects and may be recommended by your doctor.
Immunotherapy Injections versus Sublingual Immunotherapy
Immunotherapy has been given by injection for more than 100 years and many studies prove that it is effective. A number of studies published in the last 5 years have shown that very high dose sublingual immunotherapy (SLIT), where allergen extracts (drops or tablets) are retained under the tongue for a few minutes, then swallowed, can also be effective. SLIT has a longer history of use in Europe than in Australia and New Zealand, where it is used more commonly than injected immunotherapy.
The allergen extracts currently available for oral and injected therapy are very potent, and are NOT the extremely weak and ineffective extracts used by some medical practitioners ten or more years ago
It is important to inform your doctor about any reactions you may have experienced after your last injection and any new medications you are taking (such as eye drops, new heart/blood pressure tablets) or if you become pregnant.
Patients who are pregnant (or planning to become pregnant in the near future) are not routinely commenced on allergen immunotherapy until after they have given birth. If the patient is on maintenance doses of allergen immunotherapy and then becomes pregnant, the injections can be continued (unless the patient wishes to stop), but the supervising specialist should be contacted to discuss relevant safety issues.