When a small stimulus has a big effect

Why do we sneeze?

Sneezing is a natural reflex in which air is suddenly and forcefully expelled through the nose and mouth. This process is triggered by irritation of the nasal mucosa. The irritation can be caused by foreign particles such as pollen, house dust mites or animal hair, but also by other influences like sudden exposure to bright light.

When such irritation occurs, the affected nerve cells send signals via the trigeminal nerve to the brainstem. This leads to a coordinated activity of various muscles involved in the sneeze. These include the facial muscles, those in the neck and chest, and the diaphragm, which contracts forcefully. At the same time the head tilts backwards while the vocal cords in the larynx briefly close to produce the strong burst of air.

Physiologically, sneezing is a form of breathing characterised by speed and explosiveness and involves the same muscles that are used in normal respiration. Unlike conscious control or even deliberate interruption of breathing, sneezing is a reflex that cannot be suppressed voluntarily.

What triggers sneezing?

Sneezing can be caused by a variety of triggers, mainly related to irritation of the nasal mucosa. Sneezing fits often occur in connection with inflammation of the nasal lining, caused either by allergic reactions or by infections. In the allergic form, the immune system overreacts to certain environmental substances, such as pollen, house dust mites or animal hair. This leads to typical symptoms like itching and increased sneezing.

Infectious causes usually result from a viral or bacterial infection of the upper respiratory tract, for example during a cold. Pathogens can be spread further when sneezing. Non-infectious stimuli such as certain medications, hormonal changes or environmental factors like dust, smoke, cold temperatures or strong spices can also irritate the nasal mucosa and trigger sneezing fits.

In addition to common triggers, there are also more specific and rather rare triggers that are nevertheless noteworthy. Physical exertion or emotional states can play a role – some people experience sneezing in situational contexts, for example after intense sexual arousal. There are also cases in which sneezing attacks are associated with certain neurological disorders or occur as a symptom accompanying headache attacks.

Why does sunlight make some people sneeze?

The phenomenon where some people sneeze when looking into bright sunlight is called the photic sneeze reflex. It is thought to be due to a genetically determined peculiarity in the nervous system.

In affected individuals certain nerves in the head lie unusually close together, particularly the trigeminal nerve, which serves the face, nose and parts of the jaw, and the optic nerve, which transmits visual impressions from the eye to the brain. Strong light stimulation from a sudden look at the sun can cause nerve impulses to cross over. Stimulation of the optic nerve can spill over to the trigeminal nerve. This is mistakenly interpreted as a signal to trigger a sneeze reflex.

This reaction occurs mainly when there is a sudden change from a dark to a very bright environment and not necessarily due to brightness alone. Sunglasses therefore often provide only limited protection, as the reflex can be triggered before the eyes are fully shielded.

Although the photic sneeze reflex is usually harmless in daily life, it is advisable, especially when cycling or driving, to be prepared. Sneezing is associated with the instinctive closing of the eyes, which briefly impairs perception.

Is frequent sneezing a good sign?

Frequent sneezing is in many cases a sign that the body is actively responding to stimuli – and that is basically positive. By sneezing the body attempts to remove foreign particles or pathogens from the airways. The resulting burst of air cleans the nasal mucosa and thus helps protect against infections. In the early stages of a cold, frequent sneezing also indicates that the immune defences are becoming active and the mucosa is reacting to intruders.

However, frequent sneezing is not always harmless. It can also indicate allergies, dry indoor air or a sensitive nasal mucosa. If sneezing persists for a long time or is accompanied by other symptoms such as itching, watery eyes or breathing problems, medical evaluation should be sought.

How can you suppress a sneeze?

From a medical perspective, deliberately suppressing a sneeze, for example by pinching the nose or closing the mouth, is not recommended because it can carry considerable risks. When sneezing, air streams out of the lungs at very high speed, comparable to a gale. This causes a strong build‑up of pressure in the airways.

If this reflex is suppressed, the built‑up force is not released outward. Instead it can damage the tissue of the nasal mucosa. Tiny tears may form through which pathogens can enter normally protected areas such as the sinuses or the middle ear. This can lead to infections and, in the worst case, to eardrum injuries. Other potential complications include dizziness, diaphragm injuries or the rupture of small blood vessels.

Why do we close our eyes when we sneeze?

When sneezing the eyes close reflexively, without voluntary control. This probably serves to protect the eyes from pathogens expelled during sneezing and to prevent the high pressure generated from straining the eyeballs. Closing the eyes is part of the unconscious muscular reaction of the face during a sneeze.

What to do about sneezing: practical tips

• For frequent sneezing caused by a viral infection such as a cold or flu, nasal rinses or inhalations with essential oils can help. They support cleansing the nasal mucosa and relieve symptoms.
• For a bacterial infection, a medical examination is important so that an antibiotic can be prescribed if necessary to target the pathogens and thus reduce sneezing.
• If you suffer from allergy‑related sneezing, first try to avoid the triggering allergens. This may include staying indoors during high pollen counts or fitting windows with pollen screens.
• For a house dust mite allergy, use special mite‑proof covers for mattresses and pillows. Also wash your bedding regularly at at least 60 °C to kill mites and reduce nasal irritation.
• The use of air purifiers and filters in living spaces can help significantly reduce the concentration of allergenic particles such as dust and pollen in the air and thus prevent sneezing attacks.
• Make sure to wash cuddly toys or other textiles that may harbour allergens regularly, or alternatively freeze them for several hours to kill house dust mites.
• In allergies, saline nasal sprays can be used to moisten the mucosa, wash out allergens and soothe the inside of the nose. This can be a helpful step before using corticosteroid nasal sprays.
• Antihistamines help suppress the allergic reaction that triggers sneezing fits. Take them as tablets or as nasal sprays according to recommendations to relieve symptoms.
• To prevent the spread of viruses and bacteria, sneeze into a disposable tissue and dispose of it immediately. This protects other people from infection.
• If no tissue is at hand, sneeze into your elbow. This is better than sneezing into your hands, as it limits the spread of pathogens.
• Always wash your hands thoroughly after sneezing or blowing your nose to prevent transferring pathogens to surfaces or other people.
• Regular vacuuming with a vacuum cleaner equipped with a HEPA filter reduces the amount of house dust and allergens in your home and thus decreases sneezing attacks.
• Regular household cleaning, including dusting furniture and curtains, reduces allergen load in the environment and can help reduce sneezing.
• Keep a symptom diary to document your sneezing attacks and accompanying complaints. This makes it easier for your doctor to recommend a targeted and individual treatment.
• If sneezing persists for an extended period or causes very severe symptoms, seek medical advice. An allergy test will clarify whether a targeted treatment is appropriate.

Although sneezing is often perceived as annoying, it fulfils an important protective function for our health. With proven strategies and a little attention, frequent sneezing attacks can be reduced so that you feel more comfortable in any situation.