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What Causes Allergies During Pregnancy?

Medically Reviewed by Mary Sweeney, BSN, RN, CEN
Updated
Is it allergies or just pregnancy congestion?

Have you noticed a difference in your allergy symptoms as your pregnancy unfolds? Have you developed sneezing, coughing, and itchy eyes since becoming pregnant? Is it getting harder to control your symptoms?

Allergies are never fun, and they can be even worse during pregnancy. New symptoms may crop up, and you may have questions and concerns about what you can safely take or if your allergies may harm your growing baby.

Why does pregnancy seem to trigger allergies? What can you do about it? We’re here to answer your questions and hopefully offer a little peace of mind, if not some relief from your allergies.


What Causes Allergies?

To make sense of why you’re struggling with allergies during pregnancy, first, let’s talk about what an allergy is.

Allergies happen when our body’s immune system reacts to a foreign substance (also known as an allergen) such as pollen, dust, or a bee sting. During this reaction, our body creates antibodies — special cells to fight off the foreign substance. These cells, called mast cells, detect the “invader” and begin their work (1).

Mast cells are like watchtowers, looking out for anything dangerous. If they detect it, they will release a chemical called histamine, which is a beacon for our white blood cells to fight the invasion.

Our white blood cells then arrive and attack the problem. White blood cells are like the soldiers of our immune systems. Some white blood cells are specialized and will only attack specific invaders. Others are general and will attack anything our bodies think might be a threat.

However, the problem cells are not the only cells hurt during the attack. Often, a few damaged cells from our own bodies and even some healthy cells are targeted too — a sort of “friendly fire” situation.

This process can make our bodies swell and grow warm, which helps us fight the invader more effectively and calls more white blood cells to the area. When this happens in response to something most people can handle, we consider it an allergic reaction (2).

Allergies are common, and the most serious allergic reactions are, thankfully, incredibly rare. The worst reaction is known as anaphylaxis, where a person has such an inflammatory reaction that they may stop breathing. Luckily, while this does happen, it represents just a small percentage of allergies.
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Editor's Note:

Mary Sweeney, BSN, RN, CEN

What Are Some Signs I Have an Allergy?

In most cases, allergy symptoms can be relatively mild.

You could have an allergy if you experience:

  • Sneezing.
  • Coughing and wheezing.
  • A blocked, stuffy, or runny nose.
  • Red, itchy, watering eyes.
  • Blurred vision.
  • A red, itchy rash.
  • A raised area of skin.
  • Worse asthma or eczema.

Some people may suffer other reactions, called sensitivities and intolerances. These are not mast cell reactions, but they are still very unpleasant.

A sensitivity is when the usual effects of something are exaggerated. For example, coffee may cause palpitations in people with sensitivities.

An intolerance is where you suffer symptoms not involving the immune system. For example, acid reflux or vomiting when a lactose intolerant person drinks milk.

They Can Get Better

In some cases, allergies will get better and go away with time. The theory is that a person becomes accustomed to the allergen over time and the body stops reacting to it.

Can Pregnancy Affect Allergies?

Allergies can go either way when you’re pregnant.

A third of women with allergies experience relief from their symptoms during pregnancy.

Unfortunately, one-fifth to a quarter of women experience allergies during pregnancy. And of those with allergies, one-third will experience worse symptoms than usual.

Because of how pregnancy affects your body, you may feel as though your allergy symptoms are worse. Symptoms may also feel worse because they are combined with pregnancy symptoms.

  • Congestion during pregnancy is very normal, and if you have hay fever or another allergy to airborne substances, you may find yourself feeling particularly stuffy during pregnancy.
  • Skin stretching during pregnancy can make eczema and psoriasis worse too. Because your skin is stretched to the limit, you might experience itching on your belly, breasts, and buttocks, or even splitting and bleeding along stretch mark areas. Make sure to use a moisturizing or stretch mark cream to help you cope with the stretching. In extreme cases, a topical steroid cream may be safe during pregnancy, but speak with your health care provider before trying new products.
  • Some of the most extreme changes can happen in people who have food sensitivities or intolerances. Because of changes in your tastes and digestion during pregnancy, you might find that something you used to eat is now impossible to handle. This is especially true for people with milk allergies or gluten intolerance. The extra sensitivity could last into breastfeeding and beyond (3).

Can You Develop Allergies When You Are Pregnant?

Some women experience allergies for the first time while pregnant. However, most of the time, it affects someone who had the same allergy during childhood or who has another allergy.

This can be a bit of a surprise, especially if you did not have any allergies at all before getting pregnant.

And remember, some pregnancy symptoms can mask allergies. You might think you just have the usual stuffy nose that comes with pregnancy, but if it goes away indoors, it might be hay fever. If it goes away while outside, it could be dust mites.

The same thing can happen for rashes, bloating, or food reactions. It could be a typical pregnancy problem, or it could be an allergy.

Find Out For Sure

If you are in doubt, you should see your doctor about your symptoms.

Testing for Allergies During Pregnancy

If you have allergy symptoms that are driving you crazy, you might want to consider getting an allergy test. An allergy test is usually done one of two ways.

1. RAST Test

The first is with a process called RAST (radioallergosorbent), where your doctor or allergist takes some blood from you that they send to be tested for reactions.

Pros

  • It’s done outside the body.
  • Many allergies can be tested at once.

Cons

  • You don’t know right away.
  • It can’t test for every allergy.

2. Scratch Test

Another allergy test that allergists can do right in the clinic is a scratch test. For this one, they make a very light scratch on your skin, usually on the arm, and put a tiny drop of the allergen on the scratch.

If the area swells up and turns red, you are allergic to that substance.

Pros

  • Can test for almost any allergy.
  • You know right away.

Cons

  • Not as safe; severe reactions can occur, although rare.
  • Results can be confusing if you have a very strong reaction.

Usually, allergy tests are perfectly safe to do when you are pregnant. The RAST test is completely harmless so long as blood can be taken.

On the other hand, the scratch test has a slight risk of an extreme reaction — you could suffer hives or anaphylactic shock. For this reason, a lot of allergists will not do scratch tests on pregnant women.

What Am I Allergic To?

It’s never easy to work out what you are reacting to during pregnancy because people can experience allergic reactions to anything.

Thankfully, you are more likely to suffer one of the most common allergies. Because of the way our immune systems work, these allergies are the most common of all:

  1. Grass And Tree Pollen: Also known as hay fever, you react to the pollen released by grass and tree plants.
  2. General Pollen: Can be confused for hay fever, but you will react to regular flowers too.
  3. Dust Mites: These little invisible bugs live in dirty and dusty spaces and can cause all sorts of allergic reactions.
  4. Animals: You are just as likely to be allergic to any animal, but because people keep dogs and cats, you are more likely to notice if you have a dog or cat allergy.
  5. Foods: Nuts, fruits, shellfish, eggs, and the proteins in cow’s milk can all cause reactions, not just when you eat them but even when you touch them.
  6. Insects: Some insect bites and stings can cause massive overreactions in your immune system.
  7. Medications: You are more likely to be allergic to aspirin, ibuprofen, and antibiotics than any other medication.
  8. Latex: Things like latex gloves or condoms may trigger latex allergies, which are very common.
  9. Mold Spores: A bit like tree pollen, mold releases spores into the air to reproduce. Many people are allergic to them.
  10. Chemicals in Cleaning Solutions: You could be allergic to one cleaning product, or you could have a condition called multiple chemical sensitivity, where you react to several.

You could still be allergic to anything else, of course. But these are the most likely culprits if you suddenly have an allergy.

Another way to get rid of the guesswork is to keep an allergy diary. This is especially good if you don’t have a common or obvious allergy.

By keeping notes, you can work out what all your allergic reactions have in common. When it’s narrowed down, your doctor might be able to run an allergy test to confirm what you are reacting to.

Are My Allergies a Risk to My Baby?

Allergies can affect your baby, but rarely directly. Because the placenta works like a filter, your blood never enters your baby’s body.

This is good news because it means your baby will not get your allergy this way, will likely not be affected if you eat something they are allergic to, and will not be affected by all the white blood cells racing around your body.

Eating certain foods during pregnancy will not increase your child’s risk of an allergy. The idea that eating peanuts will give your baby a peanut allergy isn’t just an old wives’ tale — it’s the opposite of the truth (4).

Eating a varied diet during pregnancy, including common allergy triggers, reduces your baby’s chance of allergies.

Some people maintain overeating of a food type during pregnancy could cause a food aversion or intolerance, but this has not been confirmed. If you are in doubt or worried your baby will not be able to handle some of your favorite foods after birth, just remember to eat a varied diet.

When it comes to allergic reactions, these can absolutely affect your baby, though. If you suffer an anaphylactic shock, the lack of oxygen can affect your baby as well as you. The same goes for asthma and other breathing reactions (5).

IMPORTANT

If you are having trouble breathing, call 911 or go to the nearest emergency room.

If you suffer a food reaction, the loss of water and nutrients could hurt your baby. Vomiting, diarrhea, and just plain discomfort could all be a sign you are not digesting foods well.

Do not eat foods you are allergic, sensitive, or intolerant to, as this could deprive your baby of nutrients.

So even though you don’t need to worry about giving your baby an allergy, when you are pregnant, avoid things you know you are severely allergic to.

But when it comes to minor allergies like hay fever, although you might feel completely awful, your baby will be fine.

Treating Asthma During Pregnancy

Asthma and other conditions that affect your breathing can harm your baby. If you are not getting enough oxygen, your baby is not getting enough oxygen either.

This means you can’t leave your asthma untreated.

Weigh Your Options

Even though asthma medications can sometimes affect your baby, usually, the risk of an asthma flare-up is worse than the risk of the medication.

Most inhalers are entirely safe for use when pregnant, so if you need medication to control your asthma, using inhalers is a great option.

If you can get by without pills, it is best to stop taking them because of the risks. But if you need them to control your asthma, then you have to carry on taking them.

Always check with your doctor before stopping a medication you regularly took before getting pregnant.
Headshot of Mary Sweeney, BSN, RN, CEN

Editor's Note:

Mary Sweeney, BSN, RN, CEN

Safe Allergy Medications During Pregnancy?

The most common allergy medication is an antihistamine. These are perfectly safe.

Antihistamines, such as diphenhydramine (Benadryl), are in pregnancy category B, meaning they’ve been tested in animals and have not been found to harm the fetus. These medications are most likely safe, but you should always check with your doctor before taking any medication while pregnant.

Most hay fever medications and over-the-counter allergy medications are antihistamines.

Decongestants are more complicated, as some studies have found they can affect the growing fetus. Antihistamines and inhales should be used instead of decongestants while pregnant (6).

Immunotherapy for asthma or other allergies is perfectly safe to continue during pregnancy. Because there is a chance you will have a severe allergic reaction, you can’t start immunotherapy or increase your dose during pregnancy. Still, it’s perfectly safe to continue with the dose you took before conception.

IMPORTANT

Always talk to your doctor about the medications you are taking before conceiving or as soon as you find out you are pregnant (7).

What Can I Do About My Symptoms?

If you can’t take your usual medications for allergy relief, there are many perfectly safe ways to control the symptoms so you are not quite so uncomfortable.

  • Avoid places you might find the allergen.
  • Change your clothes and wash well after being exposed to the allergen.
  • Use an air filter, especially in your bedroom.
  • Leave pets with a friend or relative.
  • Wash your bedding more often.
  • Eat a healthy diet with lots of vegetables and reduced sugar and dairy.
  • Practice breathing exercises.

Wrapping Up

Suffering from an allergy during pregnancy can be very unpleasant, but most of the time, that’s all it is. Unless you have a severe allergic reaction, your baby is perfectly safe.

By using the appropriate medication and being careful around allergens, you can reduce or even eliminate your symptoms. And if you have any allergy concerns, talk to your doctor about your medication options.

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Medically Reviewed by

Mary Sweeney, BSN, RN, CEN

Mary Sweeney, BSN, RN, CEN is an oncology nurse navigator and freelance medical writer. Mary has 4 years of experience as an officer in the Navy Nurse Corps. including emergency/trauma, post-anesthesia, and deployment medicine.