The immune system is designed to defend against pathogens — foreign invaders like bacteria and viruses. But sometimes, it gets confused and launches an attack in response to certain foods being eaten. This is what happens to the more than 20 million people in the United States with food allergies. Up to 6 percent of kids and 4 percent of adults have food allergies, according to the Centers for Disease Control and Prevention (CDC).

Most food allergy symptoms happen within two hours of exposure to the food allergen — often, within minutes. Some people feel sick to their stomach, get dizzy, start coughing or sneezing, or feel faint. Others develop itchy rashes around their mouth or on their whole body.

Here’s more information on what these rashes might look and feel like and tips about when to seek medical treatment for yourself or your child.

Oral Allergy Syndrome

Oral allergy syndrome (OAS) is a minor allergic reaction to certain raw fruits, vegetables, and seeds. After making contact with an allergen, the mouth and lips begin to itch and might swell. OAS can also cause itchy ears and mouth hives. Fortunately, this type of reaction is rarely serious and doesn’t typically affect children before age 5.

Treatment for OAS

OAS symptoms are usually confined to the mouth area and generally don’t spread to other parts of the body. Treatment usually isn’t necessary since the symptoms tend to go away after the food is swallowed or removed from the mouth. Cooking the offending food or avoiding it altogether can help prevent a reaction in the future.

If you’re not sure what caused the reaction, your dermatologist or allergist may recommend a skin prick test or an oral food challenge to learn more about your condition.

Itchy Rash and Hives

Hives are one of the most common symptoms of a food allergy. They look like raised bumps with pale centers, similar to bug bites.

Several members of MyFoodAllergyTeam have experience with itchy skin rashes. Sometimes, they can pinpoint the cause, and other times, they aren’t sure: “The baby broke out in another rash today with a few hives,” one member wrote. “I got the rash pretty cleared, but she’s still super itchy. Not sure what exactly broke her out, but definitely going to single it out.”

Others have said:

• “I get a rash when I consume coconut oil. I itch and itch and get a rash all over my body.”
• “I had coffee a few days ago and broke out in a rash.”
• “I think my freshly picked tomatoes have given me an itchy rash!”

Hives from food allergies are usually short-lived and, in most cases, should go away within six hours. Some people break out in hives frequently and are not allergic to anything. These are called idiopathic or spontaneous hives.

Treatment for Hives

If the child or adult with allergies is stable, hives may not require medical treatment. But it never hurts to contact the doctor if you have concerns or if this is the first time you or your child is experiencing hives.

Taking a cool bath for 10 minutes can help relieve itching. In addition, over-the-counter antihistamines like diphenhydramine (Benadryl) or cetirizine (Zyrtec) may also be recommended. Ask your doctor or your child’s pediatrician if they have a preference. Some pediatricians favor cetirizine over diphenhydramine because it has fewer side effects.

Rash With a Skin Infection

“I’ve been itching a lot. I’m not certain why, but it may be dry skin. The doctor gave me a cream to use. We will see if it works,” said a MyFoodAllergyTeam member. Others responded that they get itchy when they eat something that “doesn’t agree with them” or that their “body didn’t like.”

Rashes often result from scratching. Getting the itch under control can help prevent rashes and further problems like skin infections.

“I had a rash recently and chalked it up to allergies. It was partially an allergy, and the rest was due to an overgrowth of staph. Yikes!” one member shared. “Took a long road to recovery. I’m finally out on the other side. Which came first, the allergy or the staph? I think the allergy made me scratch.”

When a rash becomes infected by pathogens on the skin or in your fingernails, it may feel hot to the touch, ooze pus, or start crusting over. The area can also become swollen and inflamed, and the skin may have a tight or shiny appearance. Impetigo (a type of strep infection of the skin) produces blisters that break and leave temporary marks and a dark yellow crust on the skin. In some cases, infections are serious and require hospitalization.

Treatment for Infected Rashes

It’s crucial to see a health care provider if you think you or your child may have an infected rash. When left untreated, skin infections could spread to other people and can sometimes be life-threatening. A doctor can diagnose the specific bacteria, virus, or fungus responsible for the infection by sending a skin sample to the lab. Then, they’ll determine whether a medicated ointment or cream or an antibiotic should be used to help clear up the infection. Your or your child’s health care provider can also provide instructions on how to properly clean and care for the infection as it heals.

Other Allergic Rashes

Although food allergies often cause itchy skin, they aren’t the only reason people get rashes. You or your child may get rashes from poison ivy, medication side effects, weather changes, eczema, or another type of reaction.

Contact dermatitis can cause a dry, scaly rash that’s itchy, often in response to harsh cleaning products or industrial chemicals. In allergic contact dermatitis, exposure to poison ivy, latex, nickel, or other substances leads to itchy skin, sometimes accompanied by blisters, bumps, and swelling.

Several medications also list skin rashes as a possible side effect. Antibiotics, diuretics (water pills), or another drug may produce discolored skin spots that spread and merge together. Drug rashes may appear pink or purple depending on your skin tone.

When To Call the Doctor

Speak with your doctor or your child’s pediatrician if the rash is new or severe or doesn’t respond well to over-the-counter treatments. To help get the right diagnosis, you can write down the timeline of symptoms and take photos of the rash. Always seek emergency medical treatment for trouble breathing. This can be a sign of anaphylaxis, which is a life-threatening allergic reaction.

Talk With Others Who Understand

MyFoodAllergyTeam is the social network for people with food allergies and their loved ones. Here, more than 40,000 members from around the world come together to ask questions, offer support and advice, and connect with others who understand life with food allergies.

What symptoms of food allergies are most common for you or your child? Have you ever experienced a severe allergic reaction that included a skin rash? Share in the comments below, or start a conversation by posting on your Activities page.