Can You Take Benadryl While Pregnant? What the Evidence Says

You're pregnant, your allergies are flaring, the hives won't quit, or you simply can't sleep — and the bottle of Benadryl in your medicine cabinet suddenly feels like a question mark. Is it safe? Will it hurt the baby? It's the kind of worry that sends you scrolling at 2 a.m.

The reassuring short answer: occasional, short-term use of Benadryl (diphenhydramine) at recommended doses is generally considered one of the more studied and reassuring antihistamine options in pregnancy. But the details matter, and it's always worth a quick check-in with your own clinician before you reach for it.

Can you take Benadryl while pregnant?

For most people, taking Benadryl occasionally during pregnancy is considered low-risk. Diphenhydramine, the active ingredient in Benadryl, is a first-generation antihistamine that was historically classified as FDA Pregnancy Category B — meaning animal studies showed no fetal risk, though controlled human data were limited.

According to the MotherToBaby fact sheet (updated December 2024), short-term or occasional use of diphenhydramine at recommended doses is not expected to increase the chance of pregnancy problems such as preterm delivery or low birth weight. It's one of the better-studied antihistamines, which is part of why clinicians often consider it relatively safe.

That said, 'generally safe' is not the same as 'take freely.' Mayo Clinic recommends trying non-medication measures first and talking with a healthcare professional before starting any allergy medicine in pregnancy, so you can weigh the benefits against any risks for your specific situation.

What does the research actually show?

The overall picture is reassuring. One study found no increased chance of miscarriage with antihistamine use, including diphenhydramine, in early pregnancy. A systematic review of antihistamine use in pregnancy concluded there is little evidence that antihistamines have teratogenic (birth-defect-causing) effects.

It's worth being honest about the gaps, too. A few studies have suggested a higher chance of birth defects with first-trimester use, but the studies do not all agree, and no consistent pattern of birth defects has been identified. In other words, the signal is not consistent or strong enough to flag diphenhydramine as a known cause of birth defects — but researchers acknowledge knowledge gaps remain.

What about the third trimester and labor?

This is where extra caution comes in. There are rare reports of uterine contractions and, very rarely, effects on the fetus linked to diphenhydramine use in the third trimester. Importantly, these reports typically involved higher doses or longer duration of use than what's recommended on the label.

Because of this, it's especially wise to talk to your obstetric provider before using Benadryl near your due date or in large or frequent doses. This isn't a reason to panic if you've taken an occasional standard dose — it's a reason to keep late-pregnancy use deliberate and clinician-guided rather than routine.

Safer or preferred alternatives for ongoing allergies

Benadryl is sedating, and first-generation antihistamines are known to cause drowsiness — increased irritability and drowsiness were reported in about 22.6% of patients taking them. If you need allergy control day after day rather than a one-off dose, a less sedating option is often a better fit.

Newer second-generation antihistamines have not been shown to increase the chance of birth defects when used as directed, and are often preferred for ongoing allergy management in pregnancy. Whatever you choose, run it by your clinician first.

• Cetirizine (Zyrtec) — second-generation, less sedating, often preferred for daily allergy control
• Fexofenadine (Allegra) — second-generation, non-drowsy option
• Loratadine (Claritin) — second-generation, less sedating
• Diphenhydramine (Benadryl) — first-generation; reasonable for occasional, short-term use
• Non-medication steps first when possible (saline rinses, avoiding triggers) as Mayo Clinic suggests

Is Benadryl safe while breastfeeding?

After delivery, the news is also reassuring. All antihistamines are considered safe during breastfeeding because only minimal amounts pass into breast milk, and those amounts would not be expected to harm a nursing infant.

The one thing to watch for: diphenhydramine can still cause sleepiness in the nursing baby, just as it can make you drowsy. If you notice your infant seems unusually sleepy or feeding poorly, mention it to your pediatrician, and consider a less sedating second-generation antihistamine for regular use.

When to call your doctor

Self-treating in pregnancy has limits. Reach out to a clinician — or seek urgent care — in the situations below, rather than relying on an over-the-counter antihistamine alone.

• You're having a severe allergic reaction with swelling of the lips, tongue, or throat, or any trouble breathing — this is an emergency, call 911
• Your hives, itching, or allergy symptoms are severe, spreading, or not improving
• You're in your third trimester or near your due date and want to use Benadryl
• You're using it frequently, in higher-than-recommended amounts, or for sleep night after night
• You have new itching of the palms and soles in late pregnancy (this can signal a liver-related condition that needs evaluation)