Mountain cedar is a type of tree that causes seasonal allergic reactions in some people. Its pollen contains allergens that may cause fever as a symptom. Other symptoms can include a dry cough, rhinitis, and conjunctivitis.

People use the term “cedar fever” interchangeably. In some cases, cedar fever refers to a low grade fever that may occur as a symptom of mountain cedar allergy. Others use the term to describe the action of the trees releasing clouds of pollen.

This article uses the term “cedar fever” to refer to allergic symptoms that occur in response to exposure to pollen from the mountain cedar tree in susceptible individuals.

Read on for more on cedar fever, including its symptoms, causes, treatment, and when to contact a doctor.

To discover more evidence-based information and resources for asthma & allergies, visit our dedicated hub.

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Aeroallergens are a type of airborne particle that can trigger allergic responses in certain people.

The allergic rhinoconjunctivitis and asthma that result from an allergic response to aeroallergens are significant medical disorders in the United States and are a major cause of:

  • morbidity
  • productivity loss
  • increasing healthcare costs

There are different types of cedar trees but mountain cedar, or Juniperus ashei, is the main species that causes allergies.

Research indicates that there may be cross-reactivity between mountain cedar and other species, including cedar and cypress trees. Cross-reactivity means that a person may be allergic to multiple substances that have similar proteins.

Mountain cedar trees are evergreen and have strong resistance to drought. They cover millions of acres in southern central U.S. and are particularly prevalent in Texas. The pollen they produce creates yellow and orange clouds around the trees.

Symptoms from mountain cedar allergy are seasonal and typically affect people during the pollen season. However, unlike other plants in the U.S., mountain cedar trees pollinate in the winter between December and January.

The symptoms of cedar fever can vary in severity, but common symptoms of the allergy include:

In some cases, a person may also experience a fever.

While rare, other symptoms of mountain cedar allergy affect the skin. For example, there have been cases of the allergy causing the following conditions:

  • allergic contact dermatitis, which results from an immune response
  • irritant contact dermatitis, where the pollen acts as an irritant rather than an allergen
  • hives

Mountain cedar produces a form of pollen containing an allergen called Jun a 1. This molecule is a type of glycoprotein, which means it can influence the immune system. Due to the arrangement of the molecular structure of the pollen, it slows down enzyme activity. This makes it a powerful antigen, which is why a person’s immune system may react strongly against the pollen.

Additionally, the pollen from the mountain cedar tree, J. ashei, does not have the thick, waxy outer layer of other cedar trees, making the major allergenic protein more accessible to exposure and able to affect a person’s body more efficiently.

Mountain cedar trees also produce vast amounts of pollen, creating pollen clouds that are so dense they resemble smoke. During the 2009–2010 pollen season, the city of Junction, in Texas, recorded the highest daily average of pollen concentration at 863 pollen grains per cubic meter (pollen/m3) and the highest hourly average at 70,367 pollen/m3.

Given the airborne nature of the allergen, it is difficult to avoid for people who live around mountain cedar trees. The allergen enters the body through the airway, where it passes into the mucosal membranes. These hydrate the pollen and cause it to release its allergens.

The main approaches to treating cedar fever currently include the following:

Avoidance can be challenging for people who live close to the trees. Each tree can produce up to 1 billion grains of pollen, and trees with diseases can produce up to three times as many pollen grains as a healthy tree.

As the pollen travels through the air, it is difficult for a person to avoid. However, there are methods of reducing the amount of pollen that gets into the home:

  • opening the doors and windows only when necessary
  • removing shoes and clothing when entering the house
  • washing before sleeping to remove pollen from the hair
  • vacuuming regularly
  • installing a high efficiency particulate air (HEPA) filter

In terms of medication, people may use different types of antihistamines as well as other treatments. These should target specific symptoms, which vary between people, so a person should speak with a healthcare professional before taking any medication for the first time.

Research indicates that allergy shots are generally an effective treatment method for cedar fever. This is a procedure where healthcare professionals administer small doses of an allergen to build up a person’s tolerance to it.

A person who is unsure whether or not they are experiencing cedar fever should consult a healthcare professional who may recommend allergy testing. A doctor will be able to suggest an appropriate treatment plan.

If people experience a severe allergic reaction, they should seek medical attention immediately. A severe allergic reaction may lead to anaphylactic shock if a person does not receive the appropriate treatment. However, it is important to note that severe allergic reactions are not common in cedar fever.

Cedar fever refers to a symptom that can result from an allergic response to the mountain cedar tree, or J. ashei. This type of tree occurs mostly in the central southern U.S. and pollinates during the winter.

Mountain cedar pollen is a potent allergen. There are several reasons for this, including the molecular shape of the pollen, which means it is able to restrict enzymes from functioning effectively, and the vast quantities of pollen that the trees produce. The pollen is airborne, making it difficult for people to avoid.

A person may manage their allergies by reducing pollen in the home, taking medications, or receiving allergy shots. A person should speak with a healthcare professional before taking any medications and receive an accurate diagnosis and treatment.