Howard LeWine, M.D., is chief editor of Internet Publishing at Harvard Health Publications. He is recognized as an outstanding clinician and teacher and is a recipient of the Internal Medicine Teacher of the Year award at Brigham and Women's Hospital. Dr. LeWine continues to practice Internal Medicine; most recently he became a hospitalist after practicing primary care for over 20 years.

Question:

I'm pregnant. Are there any medications I can take for allergies?

Answer:

The safety of using medicine during pregnancy is always a tricky question. There are very few medications that have been proven to be 100% safe for the fetus.

That being said, the reality is that pregnant women often need to take medicine. Many studies have looked at the results of pregnancies when women have taken medicine. This is especially true for allergy drugs.

The good news is that studies evaluating the safety of allergy medicines have overwhelmingly shown that they do not increase the risk of congenital abnormalities in babies.

The safest course of action is to avoid taking any medication, including over-the-counter drugs and herbal products, during the first trimester (first 12 weeks) of pregnancy. Many women have conditions that require medicine. Some of these conditions would be harmful to the developing baby if the mom-to-be stopped taking her medicine.

Doctors have the most experience with medications that have been around the longest, such as the older antihistamines. One caution — high doses of diphenhydramine (Benadryl) during the last couple months of pregnancy may induce early labor. But studies don't show that the drug causes fetal abnormalities.

The newer antihistamines such as Claritin and Zyrtec also appear to be safe, but we know less about them.

For nasal congestion, saline sprays are definitely safe since they are just salt water. The decongestant pseudoephedrine (Sudafed) in small doses has a good track record.

Inhaled and intranasal corticosteroids and cromolyn probably are safe. Because they work directly on the lining of bronchial tubes or lungs, the doses of active medication are low, with little getting into the blood stream.

You should always check with your doctor's office before taking any new medication, herb or supplement during pregnancy.