Allergies are common and often cause symptoms like sneezing, itchy eyes, and a runny nose. But what happens when you also feel warm, tired, or sick? Can allergies cause a fever?
The short answer is no—most allergies do not directly cause a fever. However, allergies can lead to other problems that might cause a fever. This article explains why, how to tell the difference between allergies and infections, and what to do if you have both.
What Are Allergies?
Allergies happen when your immune system overreacts to something harmless, like pollen, pet dander, or dust. Your body sees the allergen as a threat and tries to get rid of it by releasing chemicals like histamine.
This reaction leads to common allergy symptoms, such as:
- Sneezing
- Runny or stuffy nose
- Itchy, watery eyes
- Coughing
- Skin rashes or hives
These symptoms can make you feel tired or uncomfortable, but they don’t usually cause a fever on their own.
What Is a Fever?
A fever is when your body temperature rises above its normal range—usually over 100.4°F (38°C). It’s a sign that your body is fighting off an illness, like a virus, bacteria, or infection.
Fever symptoms often include:
- Feeling hot or sweating
- Chills or shivering
- Headache
- Muscle aches
- Weakness or fatigue
Since allergies and infections can have similar symptoms, many people wonder if their allergies are to blame for their fever.
So, Can Allergies Cause Fever?
In Most Cases, No
Allergies do not cause fever because they are not infections. When you have an allergic reaction, your body is responding to something it thinks is dangerous, but it’s not actually fighting germs.
However, allergies can lead to situations where fever is possible—but it’s usually due to a complication or another illness happening at the same time.
When Allergies Can Be Linked to Fever
Here are the most common ways allergies may be connected to a fever—even though they aren’t the direct cause:
1. Sinus Infections (Sinusitis)
Allergies can cause the sinuses to swell and create extra mucus. This can block the sinus passages, leading to a buildup of bacteria or viruses. If that happens, you could get a sinus infection, which often includes:
- Fever
- Facial pain or pressure
- Thick yellow or green mucus
- Cough or sore throat
So, while allergies don’t cause fever directly, they can set the stage for infections that do.
2. Ear Infections
Nasal congestion from allergies can also block the tubes in your ears. This may lead to fluid buildup and ear infections, especially in children. Signs of an ear infection include:
- Fever
- Ear pain or pressure
- Trouble hearing
- Irritability or trouble sleeping
Again, the infection—not the allergy—is what causes the fever.
3. Respiratory Infections
People with allergies often breathe through their mouths or have irritated airways. This makes them more vulnerable to viruses like the common cold or flu. If you catch a virus on top of your allergies, you could get:
- Fever
- Sore throat
- Body aches
- Fatigue
So, if you feel sick with a fever and body aches, you might have both allergies and a viral infection at the same time.
How to Tell the Difference: Allergy vs. Fever
It can be tricky to know whether you’re dealing with allergies or something more serious, like an infection. While both can cause symptoms such as sneezing and a runny nose, there are key differences to look out for. Allergies typically don’t cause a fever. If you’re feeling hot and your temperature is over 100.4°F (38°C), it’s more likely you’re fighting an infection like a cold or the flu.
Sneezing and nasal congestion are common in both allergies and infections, but the type of mucus can help you tell the difference. Allergies usually produce clear, watery mucus, while infections often lead to thicker, yellow or green mucus. Itchy eyes and nose are classic signs of allergies, but they rarely show up with infections. On the other hand, sore throats and body aches are more common with viral or bacterial illnesses.
Fatigue can happen with both allergies and infections, but it’s usually milder with allergies. Coughing may also occur in both cases—dry with allergies, and either dry or wet with infections. By paying close attention to these symptoms, you can better understand whether you’re dealing with allergies or an illness that may need medical attention.
Can Allergy Medications Cause Fever?
While allergies themselves don’t cause fever, some people wonder if the medications used to treat allergies might. Most allergy medicines, like antihistamines or nasal sprays, do not cause fever as a side effect. These medicines work by blocking or reducing the body’s allergic response, which actually helps reduce inflammation and other symptoms.
However, in rare cases, some people might have an allergic reaction to an allergy medication itself, which could include fever as part of a more serious reaction. This is uncommon but important to watch for. Also, some over-the-counter cold or flu remedies that are combined with allergy medicines may list fever as a potential side effect.
If you notice a fever after starting a new allergy medicine, stop using it and contact your healthcare provider to make sure the medication isn’t causing an adverse reaction.
How Allergies Affect Your Immune System
Allergies involve your immune system reacting to harmless substances like pollen or pet dander. When this happens, your immune system releases chemicals like histamine, causing symptoms such as sneezing and itching. While this response protects you from perceived threats, it can sometimes leave your immune system feeling tired or strained.
This constant immune activation from allergies can make it easier for you to catch infections, which may cause fever. In other words, allergies don’t directly cause fever, but by weakening your immune defenses, they might increase your chances of getting sick with a fever-causing infection.
Keeping allergies well-managed with medication and avoiding triggers can help your immune system stay stronger and reduce the risk of infections. This is especially important during cold and flu season or allergy season when both illnesses and allergens are common.
When to See a Doctor
If you’re not sure whether your symptoms are from allergies or something more serious, it’s always okay to ask a doctor. See a healthcare provider if you:
- Have a fever over 100.4°F (38°C) that lasts more than two days
- Notice thick yellow or green mucus
- Feel pressure or pain in your face or ears
- Have chills, body aches, or extreme tiredness
- Your symptoms get worse instead of better
These could be signs of an infection that needs medical treatment—such as antibiotics or antiviral medicine.
What to Do If You Have Allergies With a Fever
If you have both allergies and a fever, treat each condition separately:
For Allergies:
- Antihistamines (like cetirizine or loratadine) to reduce sneezing and runny nose
- Nasal sprays to reduce swelling and congestion
- Allergy eye drops for itchy, watery eyes
- Avoid allergens (keep windows closed, shower after being outside, use air filters)
For Fever or Infection:
- Rest and stay hydrated
- Use acetaminophen or ibuprofen to lower fever and relieve pain
- Monitor symptoms and call a doctor if they get worse
- Wash hands often and avoid spreading germs to others
Combining care for both conditions can help you recover faster and feel better overall.
Can Seasonal Allergies Make You Feel Sick (Even Without a Fever)?
Yes, seasonal allergies can definitely make you feel sick, even if you don’t have a fever. Many people report feeling tired, foggy, or just generally unwell during allergy season. One big reason is that allergies often cause nasal congestion and frequent sneezing, which can interrupt your sleep. Poor sleep makes it harder for your body to recharge, leaving you feeling exhausted and less able to fight off other illnesses.
Allergies also trigger inflammation in your body. This inflammation can cause muscle soreness, fatigue, and even mild aches that feel similar to the flu or a cold. Sinus congestion often creates pressure in your face and head, leading to headaches and discomfort that add to the feeling of being “sick.”
While these symptoms can make you feel miserable, they usually improve when allergy treatments reduce inflammation and congestion. Importantly, these allergy symptoms don’t include a true fever.
Can Children Get a Fever From Allergies?
Just like adults, kids don’t get a fever from allergies alone. But they’re more likely to develop ear infections or sinus infections from blocked nasal passages. These infections can cause a fever.
If your child has allergy symptoms plus a fever, talk to a pediatrician. They can help figure out if your child has an infection that needs treatment.
Final Thoughts: Allergies & Fever
Allergies can make you feel miserable, but they don’t cause fever directly. If you have a fever, it’s likely caused by a separate infection—like a cold, sinus infection, or flu. Allergies can make you more likely to get sick by irritating your nose, throat, and sinuses, but the fever comes from the infection, not the allergy.
Understanding the difference between allergies and infections can help you treat your symptoms the right way. If you’re ever unsure, don’t hesitate to reach out to a healthcare provider for advice.
