Smoking not only causes wrinkles - it can worsen the effects of acne, scientists have found.
Scarring associated with the spotty condition is more severe in smokers, research shows.
The findings provide another reason for people, especially teenagers prone to acne, to stay clear of tobacco, say experts.
Acne results in unsightly spots that can burst and damage the skin, leaving scars in the form of craters, "ice-pick" holes, or an uneven lumpy surface.
Scarring also occurs when people pick or squeeze their spots.
The new study looked at 992 sufferers afflicted by severe acne who were referred to a hospital dermatology department over an eight-year period.
Scarring was observed in 91 per cent of patients, and although smokers were not more likely to have acne scars, the damage to their skin was significantly more severe.
More than half (53.7 per cent) of smokers had moderate to severe scarring compared with just over a third (35 per cent) of non-smokers.
Dr Raman Bhutani, a member of the research team from Harrogate District Foundation Trust, said: "The correlation seen between smoking and severity of facial scarring could suggest that smoking can increase the severity of scarring in a susceptible person with acne.
"Further work is required to confirm this finding and to understand the mechanisms by which this may occur."
The findings were presented at the British Association of Dermatologists' Annual Conference in Manchester.
Nina Goad, from the British Association of Dermatologists, said: "Acne affects a huge proportion of the population, with 80 per cent of teenagers affected at some point. While for most people the disorder will eventually clear, some are left with scarring which can be for life. This can be hard to treat and can make people feel self-conscious and affect their self-esteem.
"We already know that smoking is bad for our health, so perhaps this latest finding will provide an extra impetus for people to quit."
Acne occurs when oil-producing glands in the skin become over-stimulated by certain hormones.
The build-up of oil creates an ideal environment for acne bacteria to flourish, producing inflammation and spots.