Allergy Shots During Pregnancy: Continue vs. Initiate — What Guidelines Say

Whether you can continue allergy shots during pregnancy depends on where you are in treatment. If you are already on maintenance immunotherapy and tolerating it well, US and European guidelines agree it is generally safe to continue at your current dose without escalation. The AAAAI/ACAAI Practice Parameter (2011) explicitly states that immunotherapy can be continued but is usually not initiated during pregnancy. If you have not yet started immunotherapy, guidelines recommend waiting until after delivery to begin. All decisions should be made in consultation with both your allergist and your obstetrician, who can weigh your individual allergy severity, pregnancy health, and risk profile.

If you discover pregnancy during allergy immunotherapy, the recommended approach depends on your treatment phase. If you are already at a stable maintenance dose that you have been tolerating without reactions, guidelines generally support continuing at that dose without escalation. If you are still in the build-up phase at a sub-therapeutic dose, your allergist may recommend pausing escalation or discontinuing, because the escalation phase carries higher systemic reaction risk and the dose is not yet providing therapeutic benefit. The JTFPP 2011 states: 'Discontinuation of immunotherapy should be considered if the pregnancy occurs during the build-up phase and the patient is receiving a dose unlikely to be therapeutic.' Notify your allergist as soon as you know you are pregnant.

The available safety data do not suggest that allergy shots cause harm during any trimester, but the data are primarily observational rather than from randomized trials. Metzger et al.'s 1978 study of 90 atopic women (121 pregnancies) found no excess prematurity, toxemia, or congenital malformations in women continuing SCIT throughout pregnancy, including the first trimester. The Swedish national registry study (Mitselou et al., 2022), the largest study to date with 743 AIT-exposed pregnancies, found no increased risk of adverse outcomes at any stage. The primary concern is not teratogenicity from the allergen extract, but rather the risk of systemic reactions that could cause maternal anaphylaxis — a concern that applies across all trimesters but is highest during dose escalation.

Yes, breastfeeding is not contraindicated during allergen immunotherapy. Neither the AAAAI/ACAAI Practice Parameter nor the EAACI guidelines place any restrictions on breastfeeding while continuing allergy shots. Allergen extracts are proteins administered subcutaneously in very small quantities. Even in the rare event of a local or mild systemic reaction, any trace allergen entering breast milk at these concentrations is not expected to affect a nursing infant. The guidance on SCIT during lactation is the same as for continuation during pregnancy: maintain the established maintenance dose without escalation, continue pre-injection allergy screening, and notify your allergist if you experience any reactions.

The largest study of allergy immunotherapy during pregnancy is the Swedish national registry analysis by Mitselou et al. (J Allergy Clin Immunol Pract, 2022), which reviewed 924,790 pregnancies and identified 743 with AIT exposure. They found no increased risk of congenital malformations (adjusted OR 0.90, 95% CI 0.63-1.27), preterm birth (aOR 0.98), stillbirth (aOR 0.79), or cesarean delivery (aOR 0.91). Metzger et al.'s earlier study (1978, 90 women, 121 pregnancies) similarly found no abnormal births. Shaikh et al. (2012) documented 185 pregnancies in patients continuing SLIT with zero systemic reactions. These data are reassuring for continuation but should not be extrapolated to support initiation, where the evidence base is far thinner (fewer than 30 documented initiation pregnancies across all studies).

Starting allergy shots before becoming pregnant is an excellent approach if you are planning to conceive and want immunotherapy. Completing the build-up phase and reaching a stable, well-tolerated maintenance dose before pregnancy means you can safely continue that maintenance dose throughout pregnancy without the risks associated with dose escalation. Most allergists and guidelines implicitly support this approach — it is the scenario in which continuation poses the least risk. If you have significant perennial allergies and are planning to conceive within the next year, discussing the immunotherapy timeline with your allergist proactively allows you to structure treatment accordingly.