Fever from Allergies: Allergy-induced Low-grade Temperature

A challenging diagnostic for your doctor

For most people, fever is not a symptom that is immediately associated with allergies, although your doctor could probably tell you that many allergy sufferers also complain from long-lasting low-grade fever. There is some evidence to support the idea that allergies can predispose a person to developing infections, which would explain the high temperature, but allergy-induced fever is very difficult to diagnose correctly. Furthermore, no studies to date have assessed the prevalence of this condition or what factors, such as age or type of allergy, are most likely to cause it.

Low-grade fever as a secondary infection

When you come into contact with the substance that triggers your allergy, immediately your start feeling symptoms coming on. It probably starts with nasal congestion and runny and itchy nose. Then comes the sneezing and your eyes start to water an itch. By this stage, your body has declared war on the intruder and an immune response is in full swing. As mucus production increases, consequence of histamine release, your air ways become blocked and inflamed, which is the stimulus to start coughing.

No wonder, after all this, that you feel exhausted and with a headache. This is a common symptom caused by the swollen sinuses, placing excessive pressure on the head (usually felt on the eyes, the upper teeth and cheekbones).

Sometimes, when the inflamed sinus cavity is overflowing with mucus, it creates the ideal environment for bacteria and viruses to grow, resulting in an allergy-induced infection. As your infection worsens, you may develop a low-grade fever, typically between 100 and 103 degrees Fahrenheit and start developing thick yellow-green mucus (as opposed to clear from the allergy).

Allergy-induced high temperature has been reported with mold, hay fever, medication, pet allergies, food allergies and even as a reaction to immunotheraphy sessions.

The most common secondary infection caused by allergies is sinusitis, an infection located in the sinus cavities. Other less common allergy-induced infections include bronchitis, infection of the bronchial tubes; and ear infections, which are a result of inflamed ear tubes that normally drain fluid.

How to treat the allergy and the infection?

Mild infections usually do not need treatment. However, if symptoms persist, you should receive medical assistance. Your doctor will probably prescribe antibiotics for the infection, complemented by antihistaminics to inhibit the release of histamine and alleviate the symptoms of the allergy and a decongestant to clear the air ways by reducing the swelling and inflammation in the sinus cavity.

However, as for all allergies, prevention is the best option, by avoiding contact with the substance that triggers your allergy. If left untreated, the infection could spread to other parts of the head such as ears and throat; and chest. In this extreme case, treatment with high doses of antibiotics or even hospitalisation may be needed.

Contact dermatitis can also cause fever

Contact dermatitis is a different type of allergy, in which the allergen must come into direct contact with your skin. Initial symptoms include localised dry, itchy and red skin. It may affect any part of your body, but common areas include folds of the arms, knees, face and hands. If you’re in the habit of scratching your dermatitis, there’s a high chance that it can become infected. This will seriously worsen your original symptoms, and your skin will get red, hot and painful, it may start oozing fluid and you’ll develop a temperature, as your body fights the allergy-induced infection. At this stage, it may need antibiotics for treatment.

In conclusion, fever is not really a primary allergy symptom, but the body’s response to the allergy-induced infection. Although there are endless reports of people complaining of low-grade temperature as part of their allergy, it is usually just listed as a less common symptom.

Furthermore, no studies look at the implications on the patients’ life, in particular because most of them report that medication to control the allergy is ineffective, and without controlling the allergy, the fever may remain for many months.

In addition, when a patient reports a persistent low-grade temperature to his doctor, other sources of infection will be considered and ruled out before it can be connected to allergies, thus making it extremely difficult to diagnose correctly. This probably means many trips to the doctor, trying different treatments until you realise all you can do is avoid the allergen that triggers your allergy!


– Clayman MD and Capaldo, RA (1989) Vancomycin allergy presenting as fever of unknown origin. Arch Intern Med. 149: 1425-1426
– Eross E, Dodick D and Eross M (2007) The sinus, allergy and migraine study (SAMS). Headache 47: 213-224
Finegold I, Dockhorn RJ, Ein D, Dolen WK, Oppenheimer J and Potter LH (2010) Immunotherapy throughout the decades: from noon to now. Ann Allergy Asthma Immunol 105: 328-336
– Mehele ME (2008) Allergy and migraine: is there a connection? Curr Opin Otolaryngol Head Neck Surg 16: 265-269
– NHS (2011a) Contact dermatitis – symptoms. http://www.nhs.uk/Conditions/Eczema-(contact-dermatitis)/Pages/Symptoms.aspx. Retrieved 15.02.2012.
– NHS (2011b) Contact dermatitis – complications. http://www.nhs.uk/Conditions/Eczema-(contact-dermatitis)/Pages/Complications.aspx. Retrieved 15.02.2012.
– Ozdoganoglu T and Songu M (2012) The burden of allergic rhinitis and asthma. Ther Adv Respir Dis 6: 11-23
– Rowe AH (1948) Fever due to food allergy. Ann Allergy 6: 252-259
– Ruoppi P (2009) Mold problem in the work environment – an otorhinolaryngologist’s view. Duodeim 125: 983-989

One comment

  1. I’ve had all of these symptoms. It’s no fun. The solution is to rebuild gut/GI health. Eliminate sugar/gluten and reduce mucus forming food such as dairy. Take a high quality probiotic. It takes time but this is the long-term solution. In the immediate term a heat pack to the forehead/sinuses helped me reduce headaches enough to then fall asleep.

Leave a Reply

Your email address will not be published. Required fields are marked *