When your child has a serious food allergy, a fever can feel like a red flag. Children who are allergic to peanuts and other types of food may experience a wide range of symptoms. So it’s natural to wonder if a fever means the allergy is getting worse or if something else is going on.

The good news is that food allergies don’t cause fevers. Still, fevers can show up alongside allergy symptoms for other reasons, and some illnesses can look a lot like an allergic reaction at first.

Below are five facts to help you sort out what a fever may mean for a child with food allergies — and when to call the doctor right away.

The Basics: Fever, Allergy, and the Immune System

A fever, medically known as pyrexia, happens when the body’s temperature rises above its normal range. A normal range is considered 95.9 to 99.5 degrees Fahrenheit for babies and children up to 10 years old and 97.6 to 99.6 F for those older than 10 and adults. Measuring someone’s temperature using different methods can give different results. Readings from the armpit are usually lower, oral temperatures fall in the middle, and rectal temperatures are the highest.

Pediatricians typically define a fever as a body temperature of 100.4 F or higher. A fever usually happens when the body’s immune system is fighting a foreign substance or infection.

Pediatricians typically define a fever as a body temperature of 100.4 degrees Fahrenheit or higher.

Food allergies happen when the immune system reacts to a food allergen — a particular protein in food. With allergies, the immune system has an inflammatory response and releases chemicals such as histamine that cause itching, hives, and swelling. If you’re wondering, “Does histamine cause fever?” it’s important to know that histamine does not trigger the fever response. Additionally, allergies do not trigger the release of the inflammatory proteins that cause a fever.

If your child has a fever along with food allergies, contact your pediatrician or allergist for medical advice. Here are some key points about fevers in children with food allergies.

1. Fever May Be a Sign of Infection

A fever can develop when the immune system is fighting a viral or bacterial infection. The immune system produces pyrogens, chemicals that raise the body’s temperature to help fight off the infection. The heat from pyrogens is your body’s natural way of slowing down germs that can make you sick.

Ear infections and other illnesses — like the common cold, the flu, sinus infections, or COVID-19 — can cause symptoms that look like allergies. These include a stuffy or runny nose, sneezing, coughing, watery eyes, or a sore throat. Gastrointestinal infections, whether caused by a parasite or a bacterial or viral infection, can also cause symptoms that may seem related to a food allergy, including abdominal pain or cramping, diarrhea, nausea, or vomiting.

One MyFoodAllergyTeam member was wondering, “Allergies or sinus infection? I’m not sure.”

A urinary tract infection may also cause symptoms that look like food allergies, such as nausea, vomiting, and discomfort in the lower abdomen. In children under age 2, roseola, a viral infection, can cause a fever followed by a rash that may look like an allergic reaction.

Other symptoms of infections, such as body aches, yellow or green mucus, and fever, are generally not associated with allergies. Allergic reactions involve an overreaction of the immune system and don’t directly cause infection.

Allergies are an overreaction of the immune system, not an infection.

2. Sunburn Can Cause a Fever

Sunburns can also cause many symptoms that may look like an allergic reaction, such as discolored skin (which can vary among skin tones) and blisters that may seem like a skin rash. A sunburn can also sometimes cause a fever and chills, which may need medical attention.

Overexposure to ultraviolet radiation from the sun damages the skin. This damage can trigger the immune system’s inflammatory response, similar to how it responds to an infection, which can cause fever and chills. If your child has a large sunburn, blistering, signs of dehydration, or fever, reach out to your doctor.

To help prevent sunburn, always apply sunscreen with an SPF of 30 or higher, have your child wear protective clothing, and stay in the shade to avoid direct sunlight whenever possible.

3. Fever Is a Side Effect of Some Medications

Certain medications can cause a drug-induced fever, which can be serious and may need immediate medical attention. Drugs that may cause fever include:

• Antipsychotics such as haloperidol and some antiemetics (used to treat nausea or vomiting)
• Selective serotonin reuptake inhibitors (SSRIs) and some other antidepressants
• Stimulant drugs such as amphetamines, forms of which may be prescribed to treat attention-deficit/hyperactivity disorder
• Sulfa antibiotics (medicines that contain sulfonamides)

Always talk to your doctor about potential side effects of any medications to help you recognize any adverse reactions, such as a fever.

Fever can be a side effect of medications. Always talk to your doctor about potential side effects of medications to help you recognize adverse reactions, such as a fever.

4. Some Vaccines Can Cause a Fever

Vaccines can also cause fevers in children. Vaccinations work by stimulating the immune system to create antibodies, among other immune responses, preparing the body to fight off future infections. A low-grade fever is a common side effect when a vaccine activates the immune system, and it usually goes away on its own.

5. Fever and Allergic Reaction May Occur at the Same Time

It’s possible to have symptoms of a food allergy at the same time as a fever from something else. This can be tricky to diagnose, especially if an infection or fever triggers symptoms like a rash or hives. Your child’s doctor likely will first rule out serious conditions, such as an infection. Once the fever is gone, allergy testing might be recommended to help pinpoint the cause.

One MyFoodAllergyTeam member shared their experience: “My four-year-old granddaughter has been dealing with hives and fever for the last week. Parents are getting frustrated about not knowing what’s wrong,” they said. “Doctors have no answers so far. Waiting for blood work to come back. Hoping to get her tested for food allergies soon.”

If your child’s allergy symptoms overlap with a fever, be sure to talk to your healthcare provider. They can review your child’s medical history and may recommend blood tests or other evaluations to determine the cause of the fever.

When a Fever May Be an Emergency

Fever isn’t always bad — it’s part of the immune system’s process of fighting infection. In some cases, a fever means it’s time to call the doctor right away. Contact your doctor immediately or seek emergency care if your child has a fever along with any of the following:

• A temperature over 104 F
• Extreme irritability or crying
• An unusual rash
• Sluggishness or extra drowsiness
• Severe headache or neck pain
• Trouble breathing
• Vomiting or nausea
• Seizure

Fevers are especially dangerous in newborns. Get medical care right away if your child is younger than 3 months and has a rectal temperature greater than or equal to 100.4 F, even if there are no other signs of illness.

Have a Conversation With Your Child’s Pediatrician

If your child has food allergies, it’s important to discuss fever with your doctor to better understand the signs of a serious health condition. Your doctor can guide you on how to watch for symptoms in a child with food allergies, especially when a fever may be caused by something other than an allergy.

For children with serious food allergies, you’ll need to recognize the signs of anaphylaxis. Anaphylaxis is a severe allergic reaction that can be life-threatening, so always carry emergency epinephrine.

Don’t hesitate to talk with a healthcare provider if you have questions or concerns about your child’s treatment plan. This may include over-the-counter medications like antihistamines and prescription immunotherapy for immunoglobulin E (IgE)-mediated food allergies. IgE is a type of antibody that can trigger allergic reactions. Learning more about food allergies and being prepared in case of an emergency can help you and your child navigate the challenges of living with food allergies.

Join the Conversation

On MyFoodAllergyTeam, people share their experiences with food allergies, get advice, and find support from others who understand.

Has your child had a fever that seemed linked to food allergies? What symptoms did you notice? Let others know in the comments below.