Women should avoid applying make-up while travelling to work on the train because a sudden jolt could cause them to scratch their corneas, according to an expert.
The warning, which comes as National Eye Health Week gets under way, makes a serious point in a long-standing debate about the 'etiquette' of putting on make-up while on public transport.
Dr Susan Blakeney, a clinical adviser to the College of Optometrists, also said that "good make-up hygiene" was important to keep eyes healthy.
In comments reported by The Telegraph, Dr Blakeney said that there were "simple steps, such as hand-washing and taking notice of expiry information [on eye products], that may help minimise potential risks to eye health".
She said: "The human eye is pretty resilient, but poor hygiene can lead to unpleasant infections. And the modern-day phenomenon of applying make-up on the journey to work undoubtedly increases the risk of scratching your cornea."
The "modern-day phenomenon" has divided commuters over the years, with adherents viewing it as an effective use of what would otherwise be 'dead time' on the way to work, while others who are more disapproving see it variously as inappropriate or amusing.
Emily Yoffe, who writes the Dear Prudence agony column for Slate, once responded to an enquiry by a reader on the subject saying: "I'll bet anything that your office comes equipped with a bathroom."
Also amid National Eye Health Week, a survey by the College of Optometrists revealed that over half of UK make-up users do not check the label to see how long they should keep their mascara for.
The cornea is the clear tissue at the front of the eye.Reuse content