Mom Loves Best: What Causes Allergies During Pregnancy?

A special guest blog from our friends at Mom Loves Best.

Reviewed by Mary Sweeney, BSN, RN, CEN

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 during pregnancy they can be even worse. New symptoms can crop up and you may worry about whether you can take allergy medicine without harming your growing baby. Plus, you knew pregnancy wouldn’t be a cakewalk. You expected aches and pains, but would like to be able to breathe while dealing with them!

Why does pregnancy seem to trigger your allergies? What can you do about it?

What Causes Allergies?

To make sense of what is happening, 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, or special cells to fight off the foreign substance. These cells, called mast cells, detect the “invader” and begin their work (source).

Mast cells are like watchtowers, looking out for anything dangerous. If they detect it, they will release something called a histamine, which is a beacon for our white blood cells to come and 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, not just the problem cells are 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 up and get 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 which most people can handle, we consider it an allergic reaction (source).

Allergies are common, and but the most serious allergic reactions are pretty, thankfully, incredibly rare. The most serious of reactions 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.

What Are Some Signs I Have An Allergy?

In most cases, allergy symptoms can be relatively mild. A stuffy nose, itchy, watering eyes or a cough are all very likely if you have an allergy.

You could have an allergy if you experience:

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 will 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 when they are pregnant.

Unfortunately, one-fifth to a quarter of pregnant women experience allergies anyway. 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 just feel worse because of how they combine with pregnancy symptoms.

  • Congestion during pregnancy is very normal, and if you have hay fever or another allergy to airborne substances, then you could find yourself feeling particularly stuffy during pregnancy (source).

  • Skin stretching during pregnancy can make eczema and psoriasis worse too. Because your skin is pushed to the limit, you might find that your belly, breasts, and buttocks are very itchy, or even splitting and bleeding along with the stretch mark areas. Make sure to use a moisturizing cream which does not affect your skin too badly, to help you cope with the stretching. In extreme cases, a topical steroid cream is usually safe during pregnancy.

  • Some of the most extreme changes can happen in people who have food sensitivities or intolerances. Because of changes in your sensitivity to tastes and your 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 all the way into breastfeeding and beyond (source).

Can You Develop Allergies When You Are Pregnant?

If you thought you were home free because you haven’t had allergies before, we’re going to have to burst your bubble.

Some women experience allergies for the very first time while they are pregnant. However, most of the time it affects someone who had the same allergy during childhood, or who has another allergy. That’s not always the case, but it’s pretty common.

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

And remember, some of the symptoms of pregnancy can mask allergies. You might think that you are just having 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 might be dust mites.

The same thing can happen for rashes, bloating, or food reactions. It could just be a normal 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 are having 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.

The first is with a process called RAST (radioallergosorbent), where your doctor or allergist takes some blood from you which they then send out to be tested for reactions. One option is a blood test called ELISA (enzyme-linked immunosorbent assay). Your doctor will draw a small amount of blood and send it to a lab, where it is tested for different allergies.


The first is with a process called RAST, where your doctor or allergist takes some blood from you which they then send out to be tested for reactions.


  • It’s done outside the body.

  • Many allergies can be tested at once.


  • You don’t know right away.

  • It can’t test for every allergy.

Scratch Test

Another allergy test that can be done right in the clinic is a scratch test. For this one, they make a very light scratch on your skin, usually 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 the substance that was scratched onto the skin in that area.


  • Can test for almost any allergy.

  • You know right away.


  • Not as safe, serious reactions can occur rarely.

  • Results can be confusing if you have a very strong reaction.

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

The scratch test, on the other hand, 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 the scratch tests on pregnant women (source).

What Am I Allergic To?

It’s never simple to work out what you are having an allergic reaction to 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 are reacting to the pollen released by grass and tree plants.

  2. General Pollen: Can be confused for hay fever, but you will react to normal 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 of all kinds, all sorts of fruits, shellfish of all kinds, 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, such as bee 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.

How To Track It

Another way of getting 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 sort of 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.

It has also been confirmed that 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.


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 is not confirmed. If you are in doubt or worried your baby will come out and not be able to handle some of your favorite foods, 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.


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

If you suffer from a reaction to food, 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 your foods well.

Stay Away

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, make sure to avoid things you know you are severely allergic to when you are pregnant.

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

Treating Asthma During Pregnancy

It was mentioned above that asthma, and other conditions which affect your breathing can harm your baby. This is because if you are not getting enough oxygen, your baby is not getting enough oxygen either.

This means that 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 completely safe to use when pregnant, so if you need medication to control your asthma, using only inhalers is a great option.

If you can get by without pills, then 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 took regularly before getting pregnant.

Safe Allergy Medications During Pregnancy?

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

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

Immunotherapy, for asthma or any other allergy, is perfectly safe to continue while you are pregnant. Because there is a chance you will have a serious allergic reaction, you can’t start immunotherapy or increase your dose at all when you are pregnant, but continuing at the dose you were taking before conception is perfectly safe.


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

What Can I Do About My Symptoms?

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

Consider (source):

  • Avoiding places where you might find the allergen.

  • Changing your clothes and washing well after being exposed to the allergen.

  • Using an air filter in your room, especially the bedroom.

  • Leaving pets with a friend or relative.

  • Washing your bedding more often.

  • Eating a healthy diet, with lots of vegetables and reduced sugar and dairy.

  • Practicing breathing exercises.

Wrapping Up

Suffering 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 by being careful around allergens, you can reduce or even eliminate your symptoms. And if you are unsure about anything at all, talk to your doctor about your medication options.

Posted on Fri, Mar 05, 2021