Immunotherapy or "desensitisation", is the closest thing to a cure for certain allergies, particularly for allergies to insects venom or pollen.
Immunotherapy involves the administration of gradually increasing doses of allergen extract over a period of years, given to patients by injection or sublingual drops (under the tongue). Immunotherapy alters the way in which the immune system reacts to allergens, thus switching off the allergy response to that allergen. The end result is that you become immune to that specific allergen so that you can tolerate them with fewer or no symptoms.
Immunotherapy is beneficial in certain allergic conditions
Immunotherapy is usually recommended for the treatment of potentially life-threatening allergic reactions to stinging insects.
Immunotherapy is often recommended for the treatment of severe hay fever (allergic rhinitis) due to pollen or dust mite allergy (and sometimes asthma) when:
- symptoms are severe despite maximum medical therapy
- adverse side effects of the medication
- people prefer to avoid medications
Improvement with immunotherapy does not occur immediately. It usually requires at least 4-6 months before symptoms improve, sometimes longer.
It is recommended that immunotherapy is continued for about 3-5 years, to decrease the chance that your allergies will return. Whilst undergoing immunotherapy, you can still use your allergy medications and you should continue your asthma medications in the usual way.
Allergy injections start with a very low dose. A small diabetic needle is used which may be uncomfortable, but not very painful. The dose is gradually increased on a regular (usually weekly) basis, until a therapeutic or maintenance dose is reached. This usually takes four 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 be administered in a medical facility under medical supervision.
Side effects of immunotherapy injections
Many patients develop a localised swelling at the site of the injection, which can be treated with topical antihistamine cream. If the swelling is large, your doctor may need to reduce the dose.
More serious reactions (such as wheezing, rash, dizziness or even anaphylaxis) are uncommon. Simple measures reduce the risk considerably. For example, patients are normally advised:
- to remain in their doctor's surgery for at least 45 minutes after injection
- to avoid strenuous exercising the day of the injection
- that sometimes taking an antihistamine before the injection may reduce the local itching and swelling.
It is important to inform your doctors 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).
Patients who are pregnant (or planning to become pregnant in the near future) are not routinely commenced on immunotherapy until after they have given birth. If the patient is on maintenance doses of immunotherapy and then becomes pregnant, the injections can be continued (unless the patient wishes to stop), but the supervising doctor should be contacted to discuss relevant safety issues. No increases in doses are made in pregnancy.
Sublingual Immunotherapy (SLIT)
The sublingual treatment requires no injections, fewer regular doctor visits, no waiting periods after the injections, and a lower likelihood of side effects.
In practice, those more likely to choose SLIT will be those who dislike needles, people who don't have time to wait in doctors' rooms after injections, and parents of young children, who may not wish for their child to have lots of injections.
SLIT is viewed as less effective than SCIT.
The side effects may include irritation or itching inside the mouth - this can be controlled by temporarily reducing the dose or taking an antihistamine beforehand. Mild abdominal symptoms can be experienced.
Although medications available for allergies are usually very effective, they do not cure people of their allergies. Immunotherapy is the closest thing to a "cure" for allergies that we have, reducing the severity of symptoms and the need for medication for many allergy sufferers.
Immunotherapy is not, however, a quick fix form of treatment. You need to be committed to three to five years of continuous treatment for it to work, and to cooperate with your doctor to minimise the frequency of side effects.