Allergies During Pregnancy: Safe Management and Medication Choices

Pregnancy alters immune function in ways that can intensify pre-existing allergies or, in some cases, reduce symptom severity — making allergy management during this period both medically significant and pharmacologically complex. Safe treatment requires distinguishing which medications carry evidence of fetal safety from those associated with developmental risk, a classification framework guided by the U.S. Food and Drug Administration and professional bodies such as the American College of Obstetricians and Gynecologists (ACOG). This page covers the physiological basis of pregnancy-related allergy changes, the major categories of safe and contraindicated medications, common clinical scenarios, and the decision-making boundaries that govern treatment choices. For a broader overview of the allergy landscape, the Allergy Authority home provides orientation across allergy types and conditions.

Definition and scope

Allergic disease in pregnancy encompasses the full range of IgE-mediated and non-IgE-mediated hypersensitivity responses — allergic rhinitis, allergic asthma, food allergies, skin allergies and contact dermatitis, and anaphylaxis — occurring in a patient who is pregnant. The prevalence of allergic rhinitis alone affects an estimated 18–30% of pregnant individuals in the United States, according to data synthesized in the Journal of Allergy and Clinical Immunology and referenced by ACOG in its guidance documents.

The scope of the clinical challenge is defined by three converging factors:

  1. Pharmacological restriction — A large proportion of standard allergy medications lack sufficient human gestational safety data, requiring clinicians to work from a narrower formulary.
  2. Immunological shift — Pregnancy promotes a T-helper 2 (Th2)-dominant immune state, which can amplify IgE-mediated allergic responses, particularly rhinitis and asthma, during the first and third trimesters.
  3. Fetal risk classification — The FDA's Pregnancy and Lactation Labeling Rule (PLLR), which replaced the former A/B/C/D/X letter system effective June 2015 (21 CFR §201.57), requires manufacturers to provide narrative risk summaries instead of categorical letters, placing greater interpretive responsibility on prescribers.

The regulatory context for allergy management in the United States operates under overlapping FDA labeling requirements, ACOG clinical guidance, and specialty society recommendations from the American Academy of Allergy, Asthma & Immunology (AAAAI).

How it works

Pregnancy modifies the immune system through hormonal signaling, particularly elevated progesterone and estrogen, which shift cytokine production toward the Th2 pathway. This shift suppresses certain cellular immune functions (protective against fetal rejection) but simultaneously lowers the threshold for IgE-mediated allergic responses. The nasal mucosa also becomes engorged due to increased blood volume and vascular permeability — a condition called pregnancy rhinitis that is non-allergic but frequently overlaps with and intensifies true allergic rhinitis.

Allergic asthma follows a rule of thirds: approximately one-third of pregnant patients experience worsening, one-third improve, and one-third remain stable, as documented in ACOG Practice Bulletin No. 90 on asthma in pregnancy. Poorly controlled asthma carries measurable fetal risk — including preterm birth and low birth weight — that generally exceeds the risk posed by guideline-recommended controller medications such as inhaled corticosteroids.

For anaphylaxis, epinephrine remains the first-line agent regardless of pregnancy status. The AAAAI and ACOG both affirm that withholding epinephrine during anaphylaxis poses greater maternal and fetal risk than administration. Epinephrine auto-injectors should be accessible to any pregnant patient with a documented anaphylaxis history.

Common scenarios

Scenario 1: Seasonal allergic rhinitis
A pregnant patient with pre-existing seasonal allergies experiencing nasal congestion, sneezing, and itchy eyes. First-line management begins with non-pharmacological avoidance strategies (allergy avoidance strategies). When medication is required, intranasal corticosteroids — particularly budesonide, which has the most gestational safety data — are preferred by ACOG and AAAAI over systemic antihistamines for moderate-to-severe rhinitis.

Scenario 2: Allergic asthma exacerbation
Uncontrolled asthma during pregnancy is associated with preeclampsia risk and intrauterine growth restriction. Short-acting beta-agonists (albuterol) and inhaled corticosteroids such as budesonide are considered compatible with pregnancy by ACOG. Leukotriene receptor antagonists such as montelukast carry limited human gestational data; ACOG guidance suggests continuing montelukast if a patient is already well-controlled on it, rather than switching medications during pregnancy.

Scenario 3: Food allergy management
Pregnant individuals with diagnosed food allergies require continued strict avoidance. No food allergy immunotherapy protocols are approved for initiation during pregnancy. Patients already enrolled in allergy immunotherapy programs at a maintenance dose may continue under specialist supervision, but dose escalation is contraindicated.

Scenario 4: Contact dermatitis flare
Topical low-potency corticosteroids (hydrocortisone 1%) are generally considered safe for limited skin application. High-potency topical steroids applied over large body surface areas carry risk of systemic absorption and are avoided in the first trimester.

Decision boundaries

The following structured framework governs medication decision-making in pregnancy:

  1. Non-pharmacological measures first — Allergen avoidance, HEPA filtration, saline nasal irrigation, and physical barrier methods carry no pharmacological fetal risk and are recommended as the foundation of management by both ACOG and AAAAI.

  2. Topical before systemic — Intranasal and inhaled formulations minimize systemic fetal exposure. Budesonide nasal spray and inhaled budesonide have the largest body of gestational safety data among corticosteroid options.

  3. Second-generation antihistamines over first-generation — Antihistamines such as loratadine and cetirizine are preferred over diphenhydramine for chronic use. Diphenhydramine is associated with neonatal withdrawal and uterine contractions at high doses when used near term (ACOG). Chlorpheniramine is sometimes referenced as an alternative with longer historical use data.

  4. Decongestants require trimester-specific caution — Oral pseudoephedrine is associated with gastroschisis risk in the first trimester based on case-control studies referenced in ACOG materials and is generally avoided during that window. Oxymetazoline nasal spray carries lower systemic absorption but is recommended only for short-term use (3 days or fewer) to avoid rebound congestion.

  5. Immunotherapy: maintain, do not initiate — Subcutaneous allergen immunotherapy at maintenance doses may be continued with specialist agreement. New immunotherapy courses are not initiated during pregnancy due to anaphylaxis risk during build-up phases, which cannot be safely managed with epinephrine dose escalation in the same way as in non-pregnant patients.

  6. Biologics require specialist evaluation — Dupilumab (approved for atopic dermatitis and eosinophilic asthma) falls under the PLLR narrative risk framework; human gestational data remain limited as of the FDA's product labeling, and decisions require maternal-fetal medicine involvement.

The boundary between self-managed mild symptoms and those requiring specialist involvement is defined by symptom severity, medication class, and trimester. Any patient experiencing anaphylaxis, poorly controlled asthma, or requiring systemic corticosteroid courses warrants referral to both an allergist-immunologist and an obstetrician experienced in high-risk pregnancy.

References

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