Overview of Allergy Immunotherapy
Allergy immunotherapy, sometimes called allergen desensitization or hypo-sensitization, has been around since 1911. It was introduced by Leonard Noon and John Freeman as a treatment for people with hay fever, who were found to be sensitive to grass pollen. Noon developed a procedure where he extracted timothy pollen using distilled water and then boiled it to make a special extract.
This solution was then injected into patients in increasing doses to help relieve allergy symptoms. Although we’ve tweaked the process a bit, this is essentially how allergy treatments still work today.
The term ‘immunotherapy’ now generally refers to treatments meant to fix abnormal responses of the immune system. This reset can be achieved through a process of clonal deletion (removal of certain cells), anergy (making cells less responsive), immune tolerance (getting the immune system used to certain substances), and immune deviation (altering the immune response).
You might also hear the term ‘desensitization’ being used. This is a process that develops a temporary state of tolerance in your body to substances that normally cause an allergy or hypersensitivity reaction. Moreover, what makes immunotherapy really stand out is that it can modify the course of the disease – its effects can last for a long time even after you have stopped receiving the treatment, thereby providing a preventive effect.
Anatomy and Physiology of Allergy Immunotherapy
Immunotherapy, which is a type of treatment used to boost the body’s natural defenses, works through several different actions within the body. One way it works is by controlling specific immune cells, called T-regulatory cells, which play a major role in managing your body’s immune response. These cells usually increase in your bloodstream during an allergic reaction – immunotherapy helps prevent that from happening.
Immunotherapy also helps control the activity of certain cells like eosinophils, mast cells, and basophils. These are cells that contribute to inflammation and allergic reactions.
Another way immunotherapy works is by changing the type of antibodies your body produces when it encounters an allergen. Normally, when we come into contact with an allergen, our immune system produces a type of antibody called IgE. But with immunotherapy, our body starts producing a different type of antibody, called IgG4. This type of antibody is known as a “blocking antibody,” because it helps block your body’s allergic reaction to the allergen.
Lastly, immunotherapy helps to switch your immune response from a TH2 type to a TH1 type. What does this mean? Well, TH2 immune responses tend to be associated with allergic reactions, while TH1 responses are associated with a healthier, more balanced immune reaction. This switching helps to prevent allergic reactions.
However, researchers are still studying and understanding other ways that immunotherapy impacts the body’s immune system.
Why do People Need Allergy Immunotherapy
Allergen Immunotherapy, a treatment to desensitize the body to specific allergens, is recommended in cases of:
- Severe allergies affecting the nose (allergic rhinitis)
- Allergy-induced asthma
- Allergies causing eye irritation (allergic conjunctivitis)
- Allergic reactions causing both nose and eye symptoms (allergic rhino-conjunctivitis)
- Skin allergies, also called ‘atopic dermatitis’
- Food allergies caused by an immune response (immune-mediated and IgE-mediated food allergy)
- Insect allergies that lead to critical local reactions or severe allergic reactions, also called ‘anaphylaxis’
Please note that this kind of treatment is only applicable when your reactions are triggered by an allergen and align with your symptoms. These reactions can involve a protein in your blood, known as IgE. Checking your blood for IgE levels or conducting skin tests can identify these IgE-induced reactions. Skin testing is generally more favored.
There are other types of therapies as well:
- Vaccines and biological agents, which are used to treat infectious diseases and primary immunodeficiencies – conditions in which the immune system is missing or not working properly.
- Immunosuppressive agents, which are medicines that suppress the immune system and are used in the treatment of autoimmune diseases and organ transplants.
- Biological and monoclonal agents, which are specially engineered molecules used to treat various diseases.
- Treatment for food hypersensitivity.
When a Person Should Avoid Allergy Immunotherapy
If a patient’s test for a specific allergy-related antibody (IgE) comes back negative, there’s no proof that immunotherapy, a type of treatment to modulate the immune system, would work. Also, if the test is positive but the patient’s symptoms and exposure don’t match up, then immunotherapy probably won’t be successful.
Immunotherapy should not be used alongside certain medications, such as B-blockers, because if a severe allergic reaction (anaphylaxis) occurs, the medication might interfere with the effectiveness of the adrenaline (epinephrine) used to treat it. However, for individuals who have severe allergic reactions to insect stings and also suffer from heart disease requiring these medications, the benefits of a specific type of immunotherapy (Hymenoptera venom immunotherapy or VIT) could outweigh the potential risks associated with B-blockers or ACEIs. Similarly, guidelines from the European Academy of Allergology and Clinical Immunology (EAACI) indicate that there’s no reason venom immunotherapy can’t be given to patients on B-blockers.
Immunotherapy shouldn’t be administered if the patient is experiencing an asthma attack as it could potentially worsen the attack. So, they should inform their healthcare provider about their asthma symptoms beforehand.
Equipment used for Allergy Immunotherapy
To start with, it’s vital that all extracts are kept chilled in a fridge, usually at a temperature of 4 degrees Celsius. For administering the medication, there are two common methods: one is via a minor injection under the skin, also known as subcutaneous injection; and the other is by placing it under the tongue, a method known as sublingual administration.
Next, seventy percent isopropanol, which is a type of alcohol, is needed to sanitize or clean the area before the injection is given. In addition to this, you need to have sterile, or germ-free, syringes to deliver the medication and vials to store it. It’s important to maintain a record or log of when each medication was mixed and when it needs to be used by, which is its expiration date.
It’s also necessary to have a reference guide or handbook of procedures and policies to ensure you follow the correct steps. Lastly, in any emergency situations, an epinephrine injection, which is used to treat severe allergic reactions, should be kept handy. This helps the body fight off the reaction by opening the airways and narrowing the blood vessels.
Who is needed to perform Allergy Immunotherapy?
Allergy immunotherapy, a type of treatment for allergies, can sometimes cause intense reactions like anaphylaxis (a severe, life-threatening allergic reaction). Due to this risk, a doctor should always be present to monitor the process, which carried out by well-trained staff.
These staff members need to have certain training, including:
- Knowing how to prepare allergy-triggering products
- Passing a written exam about maintaining a germ-free environment and preparing the allergy treatment
- Knowing how to clean their hands properly and sanitize the area where the mix of allergy extracts are created
- Understanding how to properly identify, measure, and combine different allergy extracts
- Understanding which patients are right for this treatment
- Talking through the risks and benefits of the procedure with patients
- Learning how to spot the signs and symptoms of a serious reaction
- Explaining to the patient what they can expect during their treatment and letting them know when it’ll be finished
Preparing for Allergy Immunotherapy
When a doctor picks out the allergen extracts for a treatment, they do so according to the results of a special test called an IgE test. This test helps them understand what you’re allergic to. They also take your specific symptoms into account. They need to consider several important details. These can include how good the allergen extracts are, whether the allergens can react to other substances in your body, and whether the allergens can break down over time. They’ll also think about the right dosage for your treatment.
For example, the starting dose should be smaller than the finishing dose. But you should know that some patients may not be able to reach this finishing, or “maintenance” dose because of potential side effects. When it comes to these maintenance doses, there is a certain range that is considered normal. This range could be different for standardized (exactly the same every time) and non-standardized (varied) extracts.
How is Allergy Immunotherapy performed
Allergen extracts, which are used for treatments like allergy shots, are made from allergenic proteins. These proteins come from things that often cause allergies, such as pollen, pet dander, dust mites, insects, and mold. However, what’s inside your allergy shot isn’t just these proteins. The final product also contains things called diluents or solvents and preservatives.
There are different types of allergen extracts, including ones that are aqueous (water-based), glycerinated (mixed with a substance called glycerin), lyophilized (freeze-dried), and made with acetone or alum.
The role of diluents is to keep the allergen in a liquid form. They’re like a liquid carrier for the allergenic proteins. The most commonly used diluents are substances called glycerin, phenol saline, and HSA.
When preparing these allergen extracts, it’s very important for the staff to maintain a clean environment. This involves good personal hygiene, washing hands thoroughly, and cleaning working areas with antiseptics. They clean the working surfaces with a water-based disinfectant first, followed by alcohol. This is because alcohol can kill organisms by dehydrating, or drying them out. This thorough cleaning process, called sanitization, helps to prevent bacteria from contaminating the allergen extracts.
Possible Complications of Allergy Immunotherapy
Allergy immunotherapy, or allergy shots, can be a great way to help control allergies. However, they should be given with extra care, since they involve exposing your body to items you know you’re allergic to. Complications can occur, including serious body-wide reactions (like anaphylaxis), large skin reactions, and reactions at the spot where the shot is given. In very rare cases, these reactions can even be fatal.
If you have asthma, especially if it’s not well-controlled, you could be at a higher risk for these complications. Other risks can come if the shot is given into a muscle by accident; this could cause a serious reaction because the allergens get absorbed by the body more quickly.
Immunotherapy can also be given under the tongue (sublingual). The first dose can cause severe reactions, but symptoms are usually milder with later doses and may include problems like a sore mouth, throat, or stomach.
Because of these risks, it’s important that you understand the possible benefits and risks of allergy shots. Generally, they should only be given under the supervision of a medical professional who specializes in this type of treatment, and after you’ve provided informed consent (meaning you’ve been given all the necessary information and agree to the treatment).
If you do experience complications, different treatments can be used to help manage them. Issues at the injection site can be managed with things like topical corticosteroids (a type of anti-inflammatory medicine), antihistamines, or cool compresses. Anaphylaxis, a severe allergic reaction, is treated primarily with a drug called epinephrine.
If you have a severe reaction to your allergy shots, your doctor will talk to you about whether the benefits of continuing the shots outweigh the risks.
What Else Should I Know About Allergy Immunotherapy?
Asthma is a chronic condition that inflames and narrows your airways. Allergic reactions can often trigger symptoms of asthma. Allergen immunotherapy, a treatment method that exposes your body to small doses of allergens to build up tolerance, can help reduce these symptoms. Still, it can sometimes lead to local or systemic reactions, meaning reactions in a specific area or throughout the body.
A 3-year treatment of either sublingual (under the tongue) or subcutaneous (under the skin) immunotherapy can prevent asthma symptoms for up to 2 years in children and young teenagers. This therapy is particularly effective when asthma is caused by grass or birch tree pollen, which also causes moderate to severe allergic rhinitis, also known as hay fever. More research is needed to understand this therapy better.
Research suggests that early immunotherapy treatment for allergic rhinitis can prevent asthma from developing in children. For example, one study found that immunotherapy for allergies to house dust mites helped prevent children from developing asthma.
Immunotherapy treatment specific to grass and birch tree pollen has been shown to decrease asthma development in children aged 5 to 12 years over a 10-year period. Another study revealed that a sublingual treatment with grass pollen resulted in fewer asthma symptoms and less need for medication.
Allergic rhinitis, or hay fever, can also greatly benefit from allergen immunotherapy. It’s been found to be effective, affordable, and disease-altering compared to standard drugs. Sublingual immunotherapy has proven helpful with symptom management and decreased the need for medication. More trials are being conducted to address safety concerns in children.
Allergen immunotherapy can also assist in relieving symptoms of rhino-conjunctivitis, another allergic reaction that affects the nose and eyes. There’s some evidence suggesting that the benefits of treatment remain even after stopping immunotherapy.
