The experience of pregnancy involves profound shifts in the body’s systems, and many women notice changes in their respiratory health and sensitivities. An allergy is an exaggerated immune response that mistakenly identifies a harmless substance, such as pollen or pet dander, as a threat, triggering symptoms like sneezing and congestion. Since pregnancy fundamentally alters the immune system and hormonal balance, pre-existing sensitivities or new respiratory issues can become a source of confusion and discomfort for expecting mothers.
Identifying Pregnancy Rhinitis Versus True Allergic Reactions
A common experience during gestation is a stuffy or runny nose. This persistent nasal congestion, which is not caused by an infection or a true allergic trigger, is known as pregnancy rhinitis (PR). The primary mechanism behind PR is the increase in circulating hormones, specifically estrogen, which leads to increased blood flow to the mucous membranes lining the nose. This heightened blood volume causes the nasal passages to swell, resulting in congestion, a runny nose, and often sleep disturbances. Symptoms frequently intensify in the second or third trimester.
Pregnancy rhinitis can affect up to 42% of pregnant individuals and typically resolves spontaneously within two weeks after delivery. Distinguishing PR from a true allergic reaction is important because the treatments differ.
True allergies, or allergic rhinitis, involve symptoms like intense itching of the nose, eyes, or throat, and watery eyes, resulting from the immune system releasing histamine in response to an external allergen.
PR symptoms usually only involve congestion and a runny nose without the characteristic itchiness or eye involvement seen with true allergies. PR symptoms are often constant and not dependent on environmental exposure, whereas true allergic symptoms fluctuate significantly based on contact with a specific trigger.
How Pregnancy Hormones Influence Pre-Existing Allergies
The hormonal environment of pregnancy necessitates a significant shift in the mother’s immune balance to ensure the fetus, which contains paternal genetic material, is not rejected. This adaptation involves the immune system moving toward a T-helper 2 (Th2) dominant state, characterized by anti-inflammatory responses and the production of certain antibodies. This Th2 skewing is largely driven by high levels of hormones like progesterone and estrogen, which suppress the pro-inflammatory Th1 immune response.
The shift toward Th2 dominance has a complex and variable impact on pre-existing allergic conditions because allergies are themselves considered Th2-mediated diseases. For conditions like asthma and eczema, which are strongly linked to Th2 activity, the pregnancy-induced immune shift can sometimes lead to a worsening of symptoms. This is due to the already-active Th2 pathways being further amplified by the hormonal changes in the body.
The effect is not uniform, however, as approximately one-third of pregnant women report that their pre-existing allergy symptoms worsen, another third find they improve, and the final third experience no change at all. Some seasonal allergies may paradoxically improve because the systemic changes also affect mast cell activity, the cells responsible for releasing histamine. The overall change is highly individualized, depending on the specific type of allergy and the unique hormonal and immune profile of the mother.
The changes in the immune system are generally temporary and resolve after delivery, as hormonal levels return to pre-pregnancy norms. Understanding this Th1/Th2 balance helps explain why women with Th1-mediated autoimmune conditions, such as rheumatoid arthritis, often experience improvement during pregnancy, while those with Th2-mediated conditions like allergies may see a flare-up.
Safe Approaches to Allergy Symptom Management
Managing allergy and rhinitis symptoms during pregnancy begins with non-pharmacological methods to minimize exposure and alleviate congestion. Avoiding known triggers, such as keeping windows closed during high pollen seasons and using air purifiers, can significantly reduce the severity of allergic reactions. Simple mechanical methods are often the first line of defense.
Saline nasal sprays and nasal irrigation, such as using a neti pot with distilled or sterile water, are considered safe and highly effective for flushing allergens and reducing nasal swelling. Elevating the head of the bed by 30 to 45 degrees at night can also help to reduce congestion and improve sleep quality.
When non-drug methods are insufficient, certain over-the-counter medications are generally considered acceptable, but consultation with a healthcare provider is necessary before starting any new treatment. Second-generation oral antihistamines, such as loratadine and cetirizine, are often recommended because they have been well-studied and have minimal side effects. These are typically preferred over first-generation antihistamines like diphenhydramine, which can cause drowsiness.
For more severe or persistent symptoms, an intranasal corticosteroid spray may be suggested by a physician, with budesonide being a well-studied and safe option. Oral decongestants like pseudoephedrine are advised to be avoided, particularly during the first trimester, and should be used cautiously later in pregnancy, especially for individuals with high blood pressure. Nasal decongestant sprays should be limited to short-term use (no more than three days) to prevent a rebound effect that worsens congestion.