SINGAPORE - You were feeling dandy just a while ago. Then suddenly, your nose becomes so congested you can hardly breathe. Your throat is coated in thick, viscous phlegm.

Wondering what could have caused this dramatic change in your health? Look out of your window it could be the weather.

According to doctors TODAY spoke to, weather shifts especially when temperatures plummet can trigger a condition called non-allergic rhinitis (or sinus in layman-speak). Rhinitis occurs when the mucous lining of the nose becomes inflamed.

Said general practitioner Dr Lily Aw, who runs a private clinic in Pasir Ris: “Changes in temperature and humidity cause the blood vessels in the nose to dilate, resulting in nasal congestion and excessive mucous production.”

Symptoms tend to show up “relatively quickly” in response to the weather changes. So, once the nasal membranes are stimulated, sinus sufferers tend to experience sneezing, a blocked or runny nose, as well as phlegm.

But don’t just blame the weather. Experiencing temperature variations while moving from one place to another for instance, returning to your freezing office from a stuffy hawker centre after lunch can also trigger a sinus attack.

“The cold air acts as a physical trigger. It’s like when cold air triggers broncho­spasm (a sudden constriction of airway muscles) wheezing in asthmatics,” explained Dr Bernard Thong, head and consultant of Tan Tock Seng Hospital’s rheumatology, allergy and immunology department.

“Occasionally, the food one eats may also make rhinitis worse,” added Dr Thong. The “noxious stimulus of the spices” found in spicy food may cause your sinuses to act up.

Viral infections, such as cold or flu, can also cause an inflammation in the nose.

Dr Aw said that from experience, such cases of non-allergic rhinitis which is commonly associated with symptoms such as body aches, tiredness, cough or fever tend to be more common during the rainy season. That’s because we tend to stay indoors more often. Windows are also closed, so ventilation is poor, making it easier to catch an infection.

Most Singaporeans also suffer from another form of rhinitis persistent allergic rhinitis. This is triggered by certainallergens such as house dust mites or animal dander, said Dr Thong. He estimated that up to 10 per cent of the adult population suffers from this.

People prone to rhinitis include asthmatics, smokers as well as women undergoing hormonal changes such as menstruation and pregnancy.

To keep your sinuses in check, Dr Aw suggested “avoiding or reducing exposure to sudden temperature and humidity changes”.

“Wearing appropriate clothing, like a sweater, when you go to a colder environment, as well as maintaining the temperature of an air-conditioned room at about 25° Celsius can help as well,” she said.

But is a stuffy nose serious enough to warrant a trip to the doctor’s? It depends, said Dr Thong.

If the symptoms are troublesome, persistent and affect sleep and other daily activities, see a doctor, he advised.

Also, rhinitis can sometimes lead to “complications like infection of the sinuses and middle ear when the swelling of the nasal mucosa blocks the opening of the sinuses and Eustachian tube”, said Dr Aw.

In such cases, a visit to the doctor’s is advised. - TODAY/ar