NEW YORK – It is cold and flu season. That means you are very likely surrounded by a symphony of coughs and sniffling noses, if you are not actively coughing yourself.

And whether your main complaint is a cough, fever, headache or runny or stuffy nose, you may notice that you tend to feel worse at night.

That is not your imagination. Several factors are to blame, starting with your circadian rhythm, which is your body’s internal clock.

When the sun sets, it tells your brain to wind down for bed and, at the same time, spurs certain immune cells to become more active. Every night, those cells are recruited to different parts of your body, on the lookout for invading viruses and bacteria.

“When they identify and try to fight off viruses, the immune cells can cause irritation and inflammation, which makes respiratory symptoms worse at night,” said Dr Diego Hijano, a paediatric infectious disease specialist at St Jude Children’s Research Hospital.

Certain hormones, such as cortisol, also follow a circadian rhythm. Cortisol levels are highest in the morning, which may help suppress inflammation during the day and tamp down symptoms. As cortisol levels begin to fall in the evening, symptoms may flare up again.

Another factor that can make cough and cold symptoms worse at night is postnasal drip, the mucus that pools at the back of your throat when you are lying down.

“Throughout the day, the accumulation of mucus is less of a problem because gravity helps drain it when you are upright and moving around,” said Dr Juan Chiriboga-Hurtado, a family medicine specialist at Keck Medicine of the University of Southern California.

But at night, mucus can build up and trigger your instinct to cough and clear your airways.

The lack of distractions, which is typically a good thing for sleep, also makes it harder to ignore your scratchy throat at night. And the environmental conditions in your bedroom, such as the dryness of the air, can irritate your respiratory tract, said Dr Chiriboga-Hurtado.

Other illnesses – like allergies, asthma and gastrointestinal reflux – are also linked to coughing that tends to worsen at night for many of the same reasons, he said. And some medicines, such as certain blood pressure drugs, might also make you cough more.

For most people with a common cold, night-time coughing should clear up in five to seven days along with other symptoms, said Dr Chiriboga-Hurtado. In some cases, a cough can linger for two weeks or more.

But if it does not improve after three weeks, it is a good idea to see a doctor to check if there may be another cause.

Fortunately, there are several home remedies that can help improve cough and cold symptoms at night.

Dr Hijano typically recommends drinking more fluids throughout the day to keep mucus thinner and to minimise the postnasal drip when you lie down.

Taking a hot bath, using a nasal saline spray or flushing your nose with a neti pot before bedtime can also thin out mucus, and these are particularly helpful for young children who cannot blow their noses, he added.

Try elevating your head with a few extra pillows to help mucus drain while you sleep. For infants, use a wedge under their mattress or prop up one side of their crib, Dr Hijano said, as pillows are not considered safe for young babies.

For adults, cough suppressants that contain dextromethorphan can provide relief by reducing the urge to cough. Cough expectorants, such as medicines that contain guaifenesin, can help loosen mucus, making it easier to expel. These are available as stand-alone drugs or in the form of combination cough-and-cold medicines.

Some combination products also include antihistamines, which can alleviate nasal congestion and reduce postnasal drip.

You can skip products that contain the ingredient phenylephrine, which a Food and Drug Administration panel recently found is not effective at reducing nasal congestion.

Another option is to use cough drops or honey, which can help prevent your throat from getting dry and irritated, Dr Chiriboga-Hurtado said.

“Coughing can be very disruptive to sleep, and sleep is essential for recovery,” he said. “So whatever you can do to help you rest will help you recover faster.” NYTIMES