Antihistamines in Pregnancy: What You Need to Know About Safety and Side Effects

When you're pregnant and battling sneezing, itchy eyes, or a runny nose, it’s natural to wonder: can I take an antihistamine? Allergies don’t take a break just because you’re expecting. In fact, about 1 in 3 pregnant women experience worsened allergy symptoms. But not all antihistamines are the same - and not all are equally safe. The good news? Several options have been studied extensively and are considered low-risk. The key is knowing which ones to use, when, and how.

First-Generation vs. Second-Generation Antihistamines

Antihistamines fall into two main groups: first-generation and second-generation. The difference isn’t just about how strong they are - it’s about how they affect your body.

First-generation antihistamines like chlorpheniramine (ChlorTrimeton), diphenhydramine (Benadryl), and dexchlorpheniramine cross into your brain. That’s why they make you drowsy. But that same trait is why they’ve been used for decades - since the 1940s and 1950s - with no clear link to birth defects. Studies tracking thousands of pregnancies show these drugs don’t increase the risk of major malformations. The American College of Obstetricians and Gynecologists (ACOG) and the American Academy of Family Physicians (AAFP) both list chlorpheniramine as a top choice for pregnancy because of this long safety record.

Second-generation antihistamines like loratadine (Claritin), cetirizine (Zyrtec), and fexofenadine (Allegra) were designed to avoid the brain. They don’t cause drowsiness in most people. That’s a big plus if you’re trying to work, drive, or care for other kids. While they haven’t been around as long, data from the National Birth Defects Prevention Study and other large databases show no consistent pattern of harm. The Mayo Clinic and ACOG now say loratadine and cetirizine “may also be safe” during pregnancy. In practice, they’re often the first choice because they work well without the side effects.

What the Experts Say

Major medical groups agree: untreated allergies can be risky. Severe nasal congestion can lead to poor sleep, difficulty eating, or even worsening asthma. That’s worse for you and your baby than taking a well-studied antihistamine.

The American College of Allergy, Asthma & Immunology (ACAAI) reminds doctors that if allergies are keeping you from sleeping or eating, treatment isn’t optional - it’s necessary. The same goes for chronic hives or eczema that won’t quit. These conditions can raise stress hormones, which may affect pregnancy outcomes.

Here’s what the top sources recommend:

• ACOG (March 2025): Chlorpheniramine is first-line. Loratadine and cetirizine are acceptable alternatives.
• Mayo Clinic: Loratadine and cetirizine are preferred for mild symptoms. For moderate to severe cases, they suggest pairing an antihistamine with a steroid nasal spray like budesonide or fluticasone - both considered safe in all trimesters.
• AAFP: Both first- and second-generation antihistamines show no increased risk of birth defects. Evidence rating: B (based on consistent observational data).

One thing all agree on: avoid pseudoephedrine in the first trimester. This decongestant, often found in combination cold meds, has been linked to a small but real risk of abdominal wall defects like gastroschisis. ACOG says it should not be used in the first 3 months. If you need it later in pregnancy, some providers may allow it at low doses (30-60 mg every 4-6 hours, max 240 mg/day) - but only if you don’t have high blood pressure.

Which Antihistamines Are Safest?

Based on decades of data and recent reviews, here’s the clearest picture:

Notice something? Chlorpheniramine, loratadine, and cetirizine appear on every top list. They’re the safest bets. Avoid hydroxyzine unless you’ve tried everything else - the data is too thin. And always check the label. Many over-the-counter products combine antihistamines with decongestants or pain relievers. You don’t need those extra ingredients.

What About Nasal Sprays?

If oral antihistamines aren’t enough, nasal sprays are often the next step. And here’s the best part: corticosteroid nasal sprays are safe during pregnancy.

Fluticasone (Flonase), budesonide (Rhinocort), and mometasone (Nasonex) don’t get absorbed into your bloodstream in significant amounts. They work right where you need them - in your nose. The AAFP and Mayo Clinic both rate these as category B for pregnancy. Many women find that using one daily cuts down their need for oral meds entirely.

For best results, use them consistently, not just when symptoms flare. It can take a few days to work. Combine them with a saline rinse for even better relief.

What to Avoid

Not all allergy meds are created equal. Here’s what to skip:

• Pseudoephedrine - Avoid in first trimester. Risk of birth defects. Use only in second/third trimester if absolutely needed and under medical supervision.
• Phenylephrine - Limited data. Not recommended as a first option.
• Combination products - Cold & flu tablets often contain antihistamines + decongestants + acetaminophen + caffeine. Stick to single-ingredient meds.
• Hydroxyzine - Too few studies. Potential risk. Save for last resort.

Practical Tips for Safe Use

Here’s how to use antihistamines wisely during pregnancy:

1. Start with the lowest dose - Use just enough to get relief. You don’t need to take more than you need.
2. Use non-drug methods first - Try saline nasal sprays, humidifiers, avoiding allergens (like dust mites or pet dander), and keeping windows closed during high pollen season.
3. Don’t self-prescribe - Even OTC meds need a conversation with your OB or midwife. They know your history and can spot hidden risks.
4. Track your symptoms - If your allergies are getting worse, it might be time to adjust your plan. Don’t wait until you’re miserable.
5. Watch for drowsiness - If you’re taking chlorpheniramine or diphenhydramine, avoid driving or operating machinery. Plan to take them at night.

When to Call Your Provider

You should reach out if:

• Your symptoms don’t improve after 3-5 days of using a safe antihistamine.
• You’re using antihistamines daily for more than 2 weeks without relief.
• You develop new symptoms like swelling, trouble breathing, or skin rashes.
• You’re unsure whether a product contains pseudoephedrine or another risky ingredient.

Remember: your health matters. If allergies are making you exhausted, anxious, or unable to eat properly, treatment isn’t a luxury - it’s part of prenatal care.