Allergies During Pregnancy: How They Impact Mom and Baby
"Uncover the surprising ways pregnancy changes your allergic reactions and what it means for your child's health."
Pregnancy brings many changes, and for women with allergies, these changes can be particularly complex. The interplay between allergy and pregnancy involves the immune system, which behaves differently to protect both mother and baby. Interestingly, the similarities between allergic reactions and the maternal-fetal interface – both involve a skewing towards a Th2 immune response – have sparked questions about whether maternal allergies could be beneficial during pregnancy.
While some studies hint at benefits like shorter time to pregnancy and longer gestational periods for allergic mothers, the overall picture remains unclear. Researchers are actively investigating how pregnancy affects the immunity of allergic and non-allergic women, seeking to understand if a strong Th2 environment influences the fetal immune system and the likelihood of postnatal allergies.
New research dives into the effects of maternal allergies on immune responses during pregnancy, looking at how the body's reaction to allergens changes and what impact these changes might have on both mother and child. This article breaks down the findings, offering insights into managing allergies during pregnancy and understanding potential implications for your baby's health.
U.S. Allergy Prevalence
The CDC reports that, among U.S. adults in 2021, 31.8% had any diagnosed allergy, 25.7% had seasonal allergy, 7.3% had eczema, and 6.2% had food allergy. These figures come from the CDC's report on Diagnosed Allergic Conditions in Adults: United States, 2021. The CDC also identifies its 2024 National Health Interview Survey as the basis for a newer data brief describing diagnosed seasonal allergies, eczema, and food allergies in U.S. adults.
Treatment Requires Careful Counseling
Management of allergic disease during pregnancy commonly requires balancing symptom control against potential medication risks. Pfaller's review notes that clinical trials in pregnant women are limited, leaving safety data for anti-allergic drugs incomplete and increasing the need to discuss benefits and known or potential risks. A later review similarly reports that concerns about drug safety can cause therapeutic hesitation and undertreatment, even though poorly controlled asthma and allergic disease are associated with adverse maternal and fetal outcomes.
The Atopic March
Research into the origins of allergic disease has focused on how allergic conditions develop from early life and how prevention might be possible. The term atopic march describes a progression that begins with atopic dermatitis and can continue to food allergy, allergic rhinitis, and asthma. Birth-cohort research emphasizes that this progression reflects complex genetic and environmental influences, while prenatal research has examined how immune responses develop during gestation and how maternal and early infant allergen exposure may affect later disease.
Decoding Allergy and Pregnancy: What the Research Reveals
A recent study explored how pregnancy modulates the production of cytokines (proteins that regulate immunity) in response to allergens in both allergic and non-allergic women. The study followed 56 pregnant women—20 with allergic symptoms (13 of whom were sensitized) and 36 without (30 of whom were non-sensitized)—collecting blood samples at multiple points during pregnancy and postpartum. Researchers measured levels of various cytokines and chemokines after stimulating the women's immune cells with common allergens (birch and cat), a mitogen (PHA), and tetanus toxoid.
- Allergen-Specific Changes: Birch allergen exposure during pregnancy increased levels of IL-5, IL-13, and CCL17 (all associated with allergic inflammation) in sensitized women. Conversely, cat allergen exposure increased IL-5 and IL-13 in non-sensitized women.
- Timing Matters: IFN-γ secretion (an important antiviral and anti-inflammatory cytokine) initially increased in the first trimester but decreased later in pregnancy in response to birch and cat allergens among non-sensitized women.
- Allergy Link: Higher levels of IL-4, IL-5, and IL-13 after allergen exposure were linked to both allergic symptoms and sensitization.
- Overall Impact: Pregnancy significantly altered the production of key cytokines and chemokines, leading to enhanced Th2 responses (a type of immune response associated with allergies) to specific allergens depending on the mother's allergic status.
Immune Changes and Allergy Risk
Recent research is examining how pregnancy-related immune changes may influence allergic responses and childhood allergy risk. In one urban-area study, 48% of pregnant women were sensitised to at least one allergen at a cutoff of 0.35 kU/L. Other work describes a pregnancy-associated Th2 bias, including decreased Th1 cytokines such as IL-2 and interferon-gamma and increased Th2 cytokines including IL-4 and IL-10, while a review identifies maternal diet as a potential influence on fetal immune development and offspring microbiome colonization.
Uncertainty Limits Treatment
Pregnancy does not produce a uniformly predictable allergy experience, and management remains difficult when symptoms and treatment concerns overlap. Pfaller's review reports that elevated Th2 responses may aggravate allergic disease when preconception control is suboptimal, while safety data for anti-allergic drugs remain limited because pregnant patients are rarely included in clinical trials. A 2026 clinical perspective describes this uncertainty across asthma, anaphylaxis, and antibody deficiency, despite efforts to provide more detailed guidance.
Relief Options Depend on Symptoms
Consumer treatment guides generally compare allergy-relief options by symptom profile, active ingredient, and dosing schedule rather than presenting one universal choice. One guide emphasizes non-pharmaceutical measures and the few antihistamines it describes as low-risk during gestation. Another advises pregnant patients to involve an obstetric provider or pharmacist when selecting medication and to consider non-medication relief steps.
What This Means for You and Your Baby
The research highlights that pregnancy significantly reshapes immune responses, particularly in how allergic and non-allergic women react to allergens. Allergic women exhibited enhanced Th2-associated responses during pregnancy to seasonal allergens like birch, while non-allergic women showed similar increases to perennial allergens like cat dander. This allergen-specific magnification during pregnancy could influence fetal immune development.
Individual Responses and Systemic Uncertainty
Pregnancy can affect allergy symptoms differently from one person to another: some people may worsen, while others experience no change or improvement. The reported explanations include hormonal changes and shifts in immune function during pregnancy. Broader research is also examining how maternal allergic responses may alter immune responses during pregnancy and what those changes could mean for the child.
Diet, Research, and Care Decisions
Studies of maternal diet and childhood allergy have not produced a single consistent conclusion: one cited study associated higher maternal intake of milk, peanuts, and wheat during the first and second trimesters with decreased mid-childhood allergy and asthma, while other studies have suggested that allergenic foods such as peanuts could increase allergy occurrence in newborns. The randomized PrEggNut Study was designed to test whether high maternal intake of eggs and peanuts during pregnancy and lactation is more effective than low intake. These differing findings illustrate why dietary decisions during pregnancy should be interpreted through the specific study design and evidence available rather than through a single broad rule.
While the study didn't explore direct effects on babies, it suggests that the immune environment during pregnancy, especially in allergic mothers, might contribute to an increased risk of allergy development in offspring. It's important to discuss any allergy concerns with your healthcare provider, who can offer personalized advice and strategies.
Ultimately, understanding how pregnancy affects your immune system can empower you to make informed decisions for your health and your baby's. Further research is needed to fully clarify the long-term consequences of these immune shifts, but these findings offer valuable insights for navigating allergy management during pregnancy.