Are you more sensitive to the change of seasons during pregnancy or since your baby arrived? You're not alone. New allergies can occur during and after pregnancy. Here's what you need to know.

By Caroline Silver
June 30, 2021
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Out of all the known side effects of postpartum recovery (backaches, baby blues, mommy tummy), there was one I never saw coming: the sudden onset of seasonal allergies.

At first, it was nothing more than an irritating stuffy nose in my first postpartum spring. But then I landed myself in a scary situation one fall afternoon alone, far into a hike when my sinuses started clogging, and breathing became increasingly difficult. This had never happened before. Thankfully, it was not life-threatening. I hurried home, threw back an antihistamine, and tried to puzzle out what was going on.

The following week I met with a doctor who confirmed a whole host of new allergy triggers. She also verified one more surprise: pregnancy can cause some people to develop new allergies.

How Pregnancy Can Impact Allergies

One word: hormones. "Hormonal fluctuations impact your allergies because estrogen and progesterone have an impact on your mast cells (allergy cells)," says Purvi Parikh, M.D., an allergist and immunologist with Allergy and Asthma Network. New allergies can emerge during periods of significant hormonal shifts, including pregnancy, postpartum, perimenopause, and menopause. "Even during menstruation, women can get more severe reactions," says Dr. Parikh. "Elevated levels of estrogen and progesterone may cause new reactions, especially to seasonal allergies."

For those with pre-existing allergies before pregnancy, reactions can vary, and there is still some mystery around why some people's symptoms differ in intensity. According to Dr. Parikh, symptoms can worsen, stay the same, or improve during pregnancy.

Pregnancy and the Immune System

We often hear the immune system is in a weakened state during pregnancy, which is why you may be more susceptible to colds and the flu. There's also a belief that the unique pregnant state of the immune system may open the door for new allergies to develop.

But what's really going on? Our immune system has two subsystems: innate and adaptive immunity—and both have varying responses to pregnancy. "During pregnancy, the immune system adapts to allow for coexistence between the mother and the fetus/placenta that contains paternal genetic material. To achieve this, the responses of the adaptive part of the immune system are reduced. This is why pregnancy is considered a state of immunodeficiency," explains Amina Abdeldaim, M.D., M.P.H., medical director for Picnic, a platform helping people take control of their allergies.

In the meantime, the innate immune response, which defends against infection, remains elevated. In this new immunological state, the body can perform two key roles—keeping the growing fetus safe from an immune system attack and protecting the mother from harmful bacterial and viral infections.

As for allergies, they are the result of an active or overactive immune system, not one that is weakened. It mistakes a non-threatening trigger, such as pollen, and attacks as though it were a potentially life-threatening pathogen. Experts conclude the relationship between the immune system and allergies during pregnancy is still at its core a hormonal issue. "The new state of the immune system results from hormones changing as hormones are what modifies the immune system—they are connected," says Dr. Parikh. "Hormones are what have a direct impact on immunity and allergies."

Do Allergies Impact the Baby?

Any new health concern can be worrying for a pregnant person, but thankfully a developing baby is unlikely to be affected by their parent's flare-ups as long as symptoms are properly managed.

Whether the baby will eventually be susceptible to allergies is primarily determined by genetics. "If one parent has any allergies, that increases the child's risk by 50 percent," explains Dr. Parikh. Environmental factors are also a cause, while alcohol and tobacco use during pregnancy are risk factors for a child developing sensitivities.

Food allergies are also not developed from a parent's food choices. The popular myth that consuming peanut butter while pregnant would lead to nut sensitivity has been proven false. Newer studies reveal that consuming peanut butter while pregnant impacts a child positively by lowering their allergy risk. The current recommendation is for pregnant people to consume a varied diet and avoid foods only if there is an existing sensitivity.

Allergies and the Fourth Trimester

The transition to a pre-pregnancy immune status begins immediately after delivery, but it can take several weeks to a few months. That's why it is possible for people to also develop new allergies in the fourth trimester. Experts say seasonal allergies, as well as dust mites, mold, animal, and skin allergies are the most common. While developing a new food allergy postpartum is possible, Dr. Parikh says those are "pretty rare."

Many people are lucky in the months following delivery, and new sensitivities tend to subside when hormones return to pre-pregnancy levels. Again, results vary, and for others, like me, allergies can persist. My postpartum allergies continue, although the symptoms are thankfully far more subdued than in the first year.

Treating Allergies During Pregnancy and Beyond

The development of allergies may not be fully understood, but it's unnecessary to suffer with no relief through pregnancy and postpartum if you're not in the lucky group. With a doctor's guidance, certain medications and nasal sprays can be used safely during pregnancy to alleviate symptoms. Make sure to reach out to your health care provider if you develop any new allergies during pregnancy or postpartum or if your symptoms worsen.

The Bottom Line

We continue to learn about how this miraculous time of transformation affects the functioning of our bodies and the immune system, but we know changing hormones can play a significant role in one's allergic state. Luckily, these changes are usually temporary and, when properly managed, won't harm the baby. Experts encourage pregnant people and new parents to seek medical help if their allergies worsen or interfere with their quality of life.