What is allergen immunotherapy?

Allergen immunotherapy – or allergy shot as they are commonly called – involves injecting your child with increasing amounts of an allergen over time. The gradual buildup of the allergen in your child's body leads to a change in their immune system; making them less likely to react negatively if they are exposed to the substance.

Allergy shots are commonly used for children who have conditions such as allergic rhinitis, allergic conjunctivitis, asthma triggered by allergies, and insect sting allergies. 

To see if allergen immunotherapy is an appropriate treatment for your child, a pediatric allergist must first confirm your child's allergen with skin prick testing or blood work. At Children's Hospital of Philadelphia, your child will be evaluated and treated by specialists from the Division of Allergy and Immunology.

Allergen immunotherapy is not recommended for all children, nor for all allergies. That said, allergen immunotherapy can be extremely beneficial for many children. In fact, a high percentage of children receiving high-dose maintenance immunotherapy will have a significant improvement in their allergic symptoms, as well as a reduction in their need for additional medication.

Immunotherapy is indicated when:

• Symptoms are moderate to severe and occur for at least several months each year
• Symptoms have not responded well to a thorough medical plan
• Medications are not desired
• Side effects of medications cannot be tolerated
• Environmental control measures have been utilized and your child cannot avoid their allergic triggers
• Improvements in your child's symptoms could begin as soon as several doses prior to or a few weeks after your maintenance dose is reached.

Generally, patients receive injections for about three to five years, at which point the symptoms usually do not return if allergen immunotherapy is stopped.

How allergy shots are administered

Your child's first injection consists of a small amount of the least concentrated extract of their allergen. Each week, the dose is gradually increased until the maintenance dose (highest concentration) is reached. There are about 24 injections that are needed; the maintenance dose is generally reached in about 24 weeks.

Once your child is receiving the maintenance dose, allergy visits are then spaced out so they receive the maintenance dose every two weeks, then every three weeks, and finally every four weeks. Our team recommends continuing monthly injections for 3-5 years. If your child is receiving allergen immunotherapy due to an insect allergy, these shots may need to continue longer.

Allergen immunotherapy injections should be given under the direct supervision of a physician. At Children's Hospital of Philadelphia, we will give your child the initial injections of each vial (of increasing concentration) in our office. Subsequent injections may be given at the hospital or at your child's pediatrician's office – whichever is more convenient for your family. Division staff will continue to closely monitor your child's progress and prescribe refills as needed.

Each time your child is due to receive a higher dose injection, they must be well on the day of the shot, without fevers or wheezing and have taken an antihistamines 30-60 minutes prior to their scheduled appointment. After the injection, your child will need to remain in our office for 30 minutes to ensure they have no adverse reactions, and refrain from strenuous activity for the next 2 hours. The reasons for these requirements are listed under potential side effects.

There are shortened schedules for allergen immunotherapy where your child can build up to the maintenance dose faster. This is not appropriate for all children and may carry an increased risk of adverse reactions. Speak to your child's allergist to see if this option in right for your child.

Potential side-effects

The drawbacks of allergen immunotherapy include: inconvenience, discomfort and the chance of adverse reactions.

Your child may have a local reaction (at the site of injection) which can occur anytime from within the first 30 minutes, up to 24 hours later. Antihistamines, ice, ibuprofen, and elevation usually control these local reactions quite well.

Systemic reactions are rare, and include allergic symptoms of the eyes and nose, hives, swelling, coughing, wheezing, and decreased blood pressure. Any severe symptoms would be initially treated at your child's allergy visit. If needed, your child will be transferred to the emergency department where life-saving medications and medical equipment is available.

Severe adverse reactions are more likely to occur if your child has a cough, is wheezing or sick before their allergy shot.

Most severe reactions occur within 30 minutes, which is why we ask you and your child to stay in the doctor's office for 30 minutes after each increased dosage. If your family cannot wait 30 minutes after the injection, your child's allergy shot will need to be rescheduled.