If you have a cold then you'd best stay indoors as the temperature drops because scientists have found keeping warm actually boosts your immune response.
Staying warm when you have a sniffle seems logical, and now US scientists have discovered that a warmer body temperature actually helps fight the common cold virus more quickly.
A new US study, published by the Proceedings of the National Academy of Sciences, reveals how body temperature affects the immune system's response to the common cold virus.
Researchers at Yale University, led by Professor of Immunobiology Akiko Iwasaki, found that the cold virus replicated more readily when the temperature in the nose of mice dipped below the core body temperature of 37C.
At the cooler temperature of 33C, key immune system proteins - known as interferons - were impaired, allowing the cold virus to reproduce and spread in airway cells.
While examining infected cells incubated at 37 or 33C, they observed that even in the absence of interferon, cells still controlled the virus, raising the possibility of additional cold-fighting mechanisms.
Further investigation, including mathematical modelling, revealed two additional mechanisms that contribute to the immune system's defence against the cold virus.
It was found that at core body temperature, infected cells die more rapidly, preventing viral replication. Secondly, an enzyme that attacks and degrades viral genes, RNAseL, is enhanced at the higher temperature.
Prof Iwasaki says the findings underscore the impact of temperature on the immune system's defences. They also offer further approaches for therapeutically tackling the cold virus, which is a key trigger of asthma.
"There are three ways to target this virus now," said Iwasaki.
Another study on fighting the cold has found zinc lozenges may also help patients recover earlier.
In fact the consumption of zinc acetate may reduce the duration of the common cold by nearly three days, according to a study.
Among the nearly 200 patients with the cold who participated in three randomised placebo-controlled trials, the effect of zinc lozenges was not affected by allergies, smoking, age or gender.
Lead author Dr Harri Hemila says patients should be encouraged to try zinc acetate lozenges as long as they don't exceed 100mg of zinc per day.
The study was published in the British Journal of Pharmacology analysis.