Allergies result from the immune system overreacting to normally harmless substances like pollen, pet dander, or dust mites. During pregnancy, the body undergoes profound physiological changes that significantly alter how it responds to these allergens. These fluctuations are directly linked to dramatic hormonal and circulatory shifts, often causing allergy symptoms to change, sometimes worsening or unexpectedly improving. Understanding these mechanisms is key to safely managing the symptoms that may arise.
The Physiological Reasons for Symptom Changes
The dramatic increase in circulating hormones is the primary driver behind altered allergy symptoms during pregnancy. Estrogen and progesterone levels rise substantially throughout gestation, influencing nearly every bodily system, including the mucous membranes and the immune response. Increased estrogen affects the nasal lining, making the tissue more reactive and prone to swelling.
This hormonal influence is compounded by the body’s overall increase in blood volume, which can rise by up to 50% during pregnancy. This greater volume of blood causes the delicate blood vessels in the nasal passages to become engorged, leading to chronic swelling, stuffiness, and congestion. This physical engorgement often mimics the feeling of severe allergic rhinitis, even without exposure to an allergen.
Furthermore, pregnancy necessitates a shift in the immune system to prevent the mother’s body from rejecting the developing fetus. This involves a change in the balance of T-helper cells, moving toward a T-helper 2 (Th2) dominance. Since the Th2 response promotes allergic reactions, this shift can lead to an increased tendency for allergic symptoms to manifest or worsen.
Differentiating Seasonal Allergies from Pregnancy Rhinitis
One of the greatest challenges during pregnancy is determining if new or worsening nasal symptoms are due to a true allergic reaction or a condition called pregnancy rhinitis. Pregnancy rhinitis is a non-allergic inflammation of the nasal lining caused solely by the hormonal and circulatory changes of gestation. This condition affects many pregnant individuals and is characterized by congestion, a runny nose, and postnasal drip lasting six or more weeks.
The key to distinguishing between the two lies in the presence of specific allergy symptoms. True allergic rhinitis, or seasonal allergies, typically involves signs of an immune reaction, such as itching in the eyes, nose, throat, or ears, often accompanied by watery eyes. In contrast, pregnancy rhinitis primarily causes congestion and stuffiness without the associated itching, and it is not triggered by specific environmental allergens like pollen or dust.
Unlike seasonal allergies, pregnancy rhinitis usually begins around the second or third month of gestation and reliably resolves shortly after delivery, typically within two weeks. Recognizing this distinction is important because it informs the choice of treatment. Consulting with a healthcare provider can help clarify the source of the symptoms.
Safe Symptom Management and Treatment Approaches
Managing allergy symptoms during pregnancy requires prioritizing the safety of both the mother and the fetus, making non-pharmacological methods the recommended first approach. Simple environmental controls can significantly reduce allergen exposure, such as using high-efficiency particulate air (HEPA) filters indoors and monitoring outdoor pollen counts. Daily nasal irrigation with a saline solution is an effective and safe way to clear irritants and moisturize inflamed mucous membranes.
When non-medication strategies are insufficient, certain over-the-counter medications can be considered, but only after consultation with a healthcare provider. Second-generation oral antihistamines, such as loratadine (Claritin) and cetirizine (Zyrtec), are generally considered safe options for use during pregnancy, particularly after the first trimester. These medications block histamine release, helping to alleviate classic allergy symptoms like sneezing and itching.
Caution must be exercised with decongestants, especially during the first trimester, due to a possible association with an increased risk of birth defects. Oral decongestants like pseudoephedrine are also known to increase blood pressure, which is a concern in pregnancy. Patients should avoid combination allergy products that contain a decongestant, often indicated by a ‘D’ suffix. Nasal steroid sprays may also be recommended by a doctor, as the medication is localized and systemic absorption is minimal.