The Difference Between an Allergic Reaction and Eczema Flare-up: What Parents Need to Know

  • Eczema may flare up when your child’s skin is exposed to any number of triggers, such as food.
  • Food allergic reactions should be reliable and reproducible. If your child has a food allergy, they’ll reliably develop an allergic reaction shortly after eating that food.
  • The red itchy rash associated with eczema is different from the hives that food allergies can cause
  • Food allergic reactions should only appear when your child is exposed to an allergen. Eczema is most often chronic or lifelong, with symptoms persisting regardless of your child’s exposure to allergenic foods
  • Eczema and food allergies belong to the atopic march. In other words, eczema is a precursor to food allergies, and eczema symptoms usually appear before food allergies. 

Food allergies and eczema are closely related, as both conditions involve the immune system. Babies with eczema are at the greatest risk of developing food allergies. Foods can not only case allergic reactions, but also eczema flare-ups.

But how can you tell the difference between an allergic reaction such as hives and an eczema flare-up to determine the best treatment? We break down what parents need to know.

What Triggers Food Allergic Reactions?

Our immune systems protect our bodies from foreign invaders, like viruses and bacteria. But when someone eats a food they are allergic to, their immune system mistakes the proteins of that food for a foreign invader. The immune system signals their body to over-defend itself against those food proteins, and this triggers an allergic reaction. 

Food Allergic Reactions: What do they usually look like?

In babies and young children, the most common signs of an allergic reaction are hives and vomiting.

Mild or moderate allergic reactions can also cause swelling of the face, lips, and eyes.

Usually, these symptoms appear seconds to minutes after someone eats a food that they are allergic to. They’ll almost always occur within 2 hours of eating the food. 

People with food allergies don’t always develop the same symptoms every time they have an allergic reaction. So, you can’t predict what an allergic reaction will look like in your child. 

Most importantly, remember that mild to moderate reactions can potentially, and quickly,  turn severe. This can happen even if your child has never had an allergic reaction before. 

Severe Food Allergic Reactions: What do they look like?

Symptoms of a severe food allergic reaction can include:

  • Swelling of the tongue
  • Swelling or tightness of the throat 
  • Struggling to swallow
  • Struggling to breathe
  • Noisy breathing
  • Persistent coughing
  • Wheezing
  • Struggling to vocalize
  • Change in voice or cry
  • Diarrhea 
  • Dizziness 
  • Collapsing or fainting 
  • Pale appearance 
  • Feeling floppy (only in infants and young children)

When a food allergic reaction causes severe symptoms in more than one organ system, it is classified as anaphylaxis. Anaphylaxis can be life-threatening.

Eczema Flare-Ups: What triggers them?

Your child’s eczema may flare up when their skin is exposed to any number of triggers. If your child has food or environmental allergies, their allergens could trigger a flare-up. In addition to allergens, dry skin, dry air, heat, existing skin infections, and irritants may also trigger eczema flare-ups.

Some irritants that may trigger flare-ups include fabrics (like polyester, nylon, or wool), fragrances (found in soaps, laundry detergents, lotions, and shampoo) chemicals and metals.

Eczema Flare-Ups: What do they look like?

Eczema makes the skin dry, red, and itchy. It can cause patches of red or dry skin, rough and itchy skin, or crusty scales and bumps that may leak fluid. These flare-ups often appear on the forehead, cheeks, scalp, knees, elbows, arm joints or leg joints. 

Eczema flare-ups v. Allergic reactions

Foods can trigger both eczema flare-ups and allergic reactions. So, how can you tell the difference?

If someone has food allergies and eczema, a food allergic reaction may make their eczema worse.

But, the red itchy rash associated with eczema is different from the hives that food allergies can cause. And as seen above, there are many other symptoms of an allergic reaction that aren’t associated with eczema (like swelling and vomiting).  

Hives caused by a food allergy. Source:

In addition, as the National Eczema Association explains, food allergic reactions are “reliable, reproducible, consistent and timely.”

If your child is allergic to a food, they’ll certainly develop an allergic reaction shortly after eating that food, every time they eat it (even though the symptoms could differ each time). Once you remove the allergens from their diet, they will no longer show symptoms of a reaction. 

But what if someone with eczema sometimes gets flare-ups when they eat a certain food, and sometimes eats that food with no issues? If they don’t show other symptoms of an allergic reaction, and don’t consistently flare up when they eat a certain food, they probably don’t have an allergy to that food.

Whenever your child appears to have a flare-up, keep track of all their surroundings, including what they ate within the past 2 hours. For example, note what fabric their clothing is made of, the soap you might have used on them, and whether their lotion or shampoo was fragranced. This can be difficult, but finding and removing other consistent eczema triggers can help you figure out whether food is an eczema trigger—or an allergen. 

Still, allergy testing is the most reliable way to determine whether your child has a food allergy. And food challenges are the only form of testing that can definitively diagnose a food allergy.

The Atopic March and Chronic Eczema

The atopic march describes how children with one allergic condition are at increased risk for others, and how allergic conditions tend to appear in a certain order (one usually “marches” after the other).

Eczema and food allergies are both considered allergic conditions, and both are part of the atopic march.  Babies usually develop eczema before food allergies, and infants with eczema are at increased risk for developing a food allergy. 

This means that the order your baby’s symptoms appear can indicate whether your baby has eczema or food allergies. Eczema is usually the first to appear. 

Most food allergic reactions like hives should go away within a few days or weeks and by avoiding the allergenic or “problem” food, should go away altogether. On the other hand, eczema can often be a chronic condition and usually starts in infancy. Chronic eczema is the most common type of eczema and can be lifelong. 

Reducing Eczema Babies’ Food Allergy Risk

If your baby is less than a year old, and does not show signs of peanut, egg, or milk allergies, ask your doctor about introducing them to peanut, egg, and milk early and often. After all, the AAP, NIH, and FDA all recommend this approach to food allergy prevention.

Feeding your baby these foods consistently, starting between 4-11 months of age, can help reduce your baby’s food allergy risk by up to 80%. This introduction is especially important for babies with eczema, because of their increased food allergy risk.

Your doctor may recommend allergy testing before you start, though, only if your baby’s eczema is severe.