Allergy Capital

immunotherapyTreating allergies with immunotherapy

 

Medicines do not cure allergies. Immunotherapy injections (also known as desensitization or allergy shots) can improve symptom severity, reduce medication use and may even reduce the risk of developing new allergies in the future.

Revised 27 January 2003

 

IMPORTANT The information provided is of a general nature and should not be used as a substitute for professional advice. If you think you may suffer from an allergic or other disease that requires attention, you should discuss it with your family doctor.

Allergies last a long time
Hay fever lasts 10-20 years in most people and those suffering from asthma as adults are unlikely to grow out of it. Medicines may help you to live with allergies but will not cure these problems. Furthermore, it is not always possible to avoid allergic triggers, such as grass pollens. Desensitization (immunotherapy) is the only way of "teaching" the immune system to tolerate allergic triggers. It is effective in most people with hay fever and often helps those with asthma. Immunotherapy is also an essential part of managing people with dangerous allergic reactions (anaphylaxis) to bee and wasp stings.

Immunotherapy: science or quackery?
Immunology is a young science whose origins lie in the study of infections in the late 19th century. It was not until the 1870's that grass pollens were identified as the likely trigger for seasonal hay fever in the UK. Skin allergy testing only became an accepted technique around 1910. It took until 1965 before IgE was identified, and another 5 years until it was found bound to tissue mast cells (see article on "What is Allergy?"). Given that the first report of immunotherapy appeared in 1911 in the Lancet, it is clear that science has lagged behind clinical practice by many decades. In fact, it is really only in the last 10-15 years that we have had a good scientific explanation for how it helps reduce the severity of some allergies.

How does immunotherapy work?
Our immune system responds to substances in our environment that we eat, drink or breathe in, but only "allergic" people develop an "allergic" immune response. Allergy injections alter the way in which the immune system reacts to allergen. By giving small but increasing amounts of allergen at regular intervals, tolerance increases. The end result is that you become "immune" to the allergens, so that you can tolerate them with fewer or no symptoms. This process is also known as specific immunotherapy, because one is trying to turn off one or more specific allergic responses. In other words, if you have injections for grass pollen allergy, it will not affect your allergy to cat or house dust mite or vice versa. In general, one tries to switch off one or two allergic responses at a time. The higher the dose tolerated without significant side-effects, the more likely is treatment successful.

Who should consider immunotherapy?

Immunotherapy is only occasionally recommended for the treatment of atopic eczema. It is not currently recommended for the treatment of food allergy, or for insect or tick bites, because it doesn't appear to work. There are commercial extracts available for the imported South American Fire Ant which was identified for the first time in Australia during 2002. Unfortunately, there are no commercially available vaccines for switching off allergy to the Australian Jumper Ant, although research in this area is currently occurring in Australia.

How old do you need to be to have injections?
There are a number of studies of immunotherapy injections in both children and adults, and it works in both groups. When dangerous allergic reactions to insect stings occur, immunotherapy may be advised regardless of age. Comfort may be increased by using ice-packs and local anaesthetic cream (like EMLA) 1-2 hours before the injection. In older patients, immunotherapy may not be recommended as they may have a reduced capacity to cope with side-effects, particularly if they suffer from major heart or lung problems

When treating non-dangerous allergies like hay fever, however, young children are generally hard to convince of the benefits! Nevertheless, young teenagers normally tolerate the slight discomfort quite well.

Desensitization and pregnancy: It is normally recommended to NOT start desensitization if you is pregnant. Some doctors also recommend stopping treatment if you became pregnant. This is not because immunotherapy has been shown to cause malformations in the developing baby. The concern is that if mum has severe allergic side-effects after an injection, then the baby's oxygen supply may be interfered with.

How well do they work?
About 3 in 4 patients with hay fever experience significant improvement with immunotherapy. Sometimes symptoms are reduced rather than abolished. In that case you may need medication as well.

In stinging insect allergy (bee, wasp), the protection against further dangerous allergic reactions to stinging insects is variously quoted at between 80 and 95 %.

Recent studies in children suggest that if immunotherapy is commenced soon after allergies first develop, it may actually reduce the risk of developing allergic reactions to other allergens, and even reduce the risk of later developing asthma.

immunotherapyimmunotherapyHow is it done?

 

 

 

 

 

desensitizationAre there lots of injections?
Yes! Allergy injections are started at very low doses. The dose is gradually increased on a regular (and usually weekly) basis, until a "maintenance" dose is reached. This usually means four to six months of weekly injections. It is a bit like climbing a staircase. Once the top maintenance dose is reached, the injections are administered less often, although still on a regular basis. Maintenance injections are normally given once per month for a few years.

What is pre-seasonal immunotherapy?
Some allergy specialists use a form of treatment called pre-seasonal immunotherapy. Injections are given approximately once per week during winter (usually June, July, August in Australia), stopping just before the spring hay fever season begins. This repeated each year for 3 - 5 years, and increasing improvement is seen year by year.

How long will you be having injections?
This form of treatment is not a "quick fix". You need to be committed for it to work, and to cooperate with you doctor to reduce the risk of side effects. If immunotherapy helps, it is normally recommended that maintenance doses be continued for an extra 3 to 5 years. This decreases the chance that your allergies will return. While this is a lot of trouble, you need to remember that you are treating a condition that might otherwise last many times that period of time.

Can you still use medicines as well?
You can still use all your allergy and asthma medicines at the same time in the usual way.

How long will the benefit last?
There are only a few long-term studies of how long the benefit of treatment lasts after the injections are stopped. They suggest that most people remain well for at least 3 years after stopping treatment. "Anecdotal experience" suggest that the benefit often lasts a lot longer, and that returning allergies are often milder than that experienced originally.

What happens if my allergies return after stopping injections?
You can use medication or restart immunotherapy if necessary.

Are other methods of immunotherapy useful?
In some countries, particularly in Europe, there is a strong tradition of undertaking immunotherapy using oral vaccines or sublingual drops. While there has been some interesting research in this area in recent years, the effectiveness of this form of treatment is difficult to compare with standard injected immunotherapy. For this reason, it is not generally recommended in Australia at this point in time.

New developments in immunotherapy
Recent animal and human studies using fragments of DNA attached to allergen offer the prospect of stimulating a potent anti-allergic immune response without the risk of allergic reactions.These vaccines are currently being trialed in humans, and have shown promising results in animal studies. Such methods offer the possibility of developing preventative allergy "vaccines" that might prevent the onset of disease if administered to children at high risk. From time to time, studies describing more convenient and less frequent treatments have been described, but these are not currently commercially available.

Side effects of desensitization

To reduce the risks of side effects, you will normally advised to:

Safety aspects of immunotherapy are discussed in an accompanying article.

References