Can allergies cause a fever?
No. Fever is not a symptom of allergies, and despite its name, hay fever does not cause one. See your doctor to find out what is causing a fever, since it may be an infection.1
Why allergies don’t cause it
Some people believe allergies can cause a fever, but ACAAI says that isn’t true: fever is not a symptom of allergies.1
Hay fever shares many symptoms with a cold, but it is not caused by a virus or bacteria.2 Its symptoms include a runny or stuffy nose and an itchy mouth, eyes or skin.1 With hay fever, a runny nose will likely have a thin, watery discharge, and you will not have a fever.2
The name causes the confusion. Hay fever is another name for allergic rhinitis, most often used for a seasonal reaction to pollen such as ragweed.2 Despite the name, it is not necessarily a reaction to hay, and it does not cause a fever.2 The label is old. John Bostock first described hay fever, or “summer catarrh,” from his own symptoms in 1819.3 Charles Blackley was the physician who first identified grass pollen as the trigger for hay fever.3
Allergies or something else?
Because fever is not a symptom of allergies, ACAAI advises asking your doctor what might be causing it. Possible causes include a bacterial or viral infection, extreme sunburn, heat stroke, inflammatory conditions like rheumatoid arthritis, some immunizations and some drugs.1
A stuffy nose with a fever deserves a second look. If you have a runny or stuffy nose and a fever, you may have a sinus infection, and sinus infections are caused by bacteria or viruses, not by allergies.1
A few clues can separate a cold or the flu from allergies. With a cold, you may have a thicker or yellowish discharge from your nose and a low-grade fever.2 A cold should clear up within several days, while allergy symptoms last as long as the exposure does.4 CDC notes that fevers are rare with a cold, while with the flu a fever is usual and symptoms start abruptly.5
When to see a doctor
See your doctor to find out what is causing a fever, since it may be an infection.1 If you have a fever that won’t go away, stiffness in your neck, severe headaches or a change in eyesight, seek immediate medical attention.1
When to get help
See an allergist if
- Allergy symptoms last for several months of the year
- Allergies bring repeated sinus problems, a blocked nose or trouble breathing
- Over-the-counter remedies don’t control your symptoms
- Allergies or asthma get in the way of daily life
- You often wheeze, cough at night or after exercise, or feel short of breath
Based on ACAAI’s “When To See an Allergist”. General information, not medical advice.
Questions
Why is it called hay fever if there’s no fever?
The name is misleading. Hay fever is another name for allergic rhinitis. Despite the name, it is not necessarily a reaction to hay, and it does not cause a fever.2
Can a sinus infection cause a fever?
Yes. If you have a runny or stuffy nose and a fever, you may have a sinus infection. Sinus infections are caused by bacteria or viruses, not by allergies.1
How can I tell a cold from allergies?
A cold is similar to allergies but may also bring a sore throat, fever and body aches, and it should clear up within several days. Allergy symptoms last as long as the exposure does.4
Sources
- Fever. American College of Allergy, Asthma and Immunology. Read on October 16, 2026.
- Hay Fever (Rhinitis). American College of Allergy, Asthma and Immunology. Read on October 16, 2026.
- The hygiene hypothesis for allergy – conception and evolution. Frontiers in Allergy. Read on October 16, 2026.
- Colds, Allergies and Sinusitis — How to Tell the Difference. American Academy of Allergy, Asthma & Immunology. Read on October 16, 2026.
- Is it a cold or flu?. Centers for Disease Control and Prevention. Read on October 16, 2026.