Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, itchy, and watery eyes, and swelling around the eyes. The fluid from the nose is usually clear. Symptom onset is often within minutes following allergen exposure, and can affect sleep and the ability to work or study. Some people may develop symptoms only during specific times of the year, often as a result of pollen exposure. Many people with allergic rhinitis also have asthma, allergic conjunctivitis, or atopic dermatitis.Allergic rhinitis is typically triggered by environmental allergens such as pollen, pet hair, dust, or mold. Inherited genetics and environmental exposures contribute to the development of allergies. Growing up on a farm and having multiple siblings decreases this risk. The underlying mechanism involves IgE antibodies that attach to an allergen, and subsequently result in the release of inflammatory chemicals such as histamine from mast cells. It causes mucous membranes in the nose, eyes and throat to become inflamed and itchy as they work to eject the allergen. Diagnosis is typically based on a combination of symptoms and a skin prick test or blood tests for allergen-specific IgE antibodies. These tests, however, can be falsely positive.
However, despite its long association with judicial hangings, one study of a series of such hangings showed that only a small minority of hangings produced a hangmans fracture.Apart from hangings, the mechanism of injury—a sudden forceful hyperextension centered just under the chin—occurs mainly with deceleration injuries in which the victims face or chin strike an unyielding object with the neck in extension. The most common scenario is a frontal motor vehicle accident with an unrestrained passenger or driver, with the person striking the dashboard or windshield with their face or chin. Other scenarios include falls, diving injuries, and collisions between players in contact sports.Although a hangmans fracture is unstable, survival from this fracture is relatively common, as the fracture itself tends to expand the spinal canal at the C2 level. It is not unusual for patients to walk in for treatment and have such a fracture discovered on X-rays. Only if the force of the injury is severe enough that the vertebral body of C2 is severely subluxed from C3 does the spinal cord become crushed, usually between the vertebral body of C3 and the posterior elements of C1 and C2. Prevention
Car crashes
Most commonly this can occur during a car accident. A person involved in a car crash, especially with no seat belt, can slam their chin against the steering wheel, dashboard, or windshield, causing the hyperextension to occur. Contact sports
Falling and colliding with other people in a contact sport can also cause this fracture. Falling causes the weight of the body to force hyperextension.