heres a paragraph or two that sums it up and a link to the site i found it from

Effects of tobacco smoke on asthmatics
The link between tobacco smoke and asthma has been the subject of many epidemiological studies and research programmes, in the UK and overseas. Active smokers and non-smokers exposed to passive smoking, (also known as environmental tobacco smoking or ETS) have been found to be adversely affected.


Recent research from Finland has shown that passive smoking plays a role in the development of adult asthma. Researchers found that subjects exposed to tobacco smoke in the workplace were twice as likely to develop asthma as those who were not exposed.[6]

Health effects for adult asthmatics include: asthma attacks; increased sensitivity and reduced lung function; irritation of the eyes, nose and throat.[7]


Most asthmatics develop a narrowing of the airways in response to small amounts of a stimuli (e.g. dust, pollen, animal skin) that triggers their condition ā?? the more severe the asthma, the more the airways will react.[8] Research carried out by the National Asthma Campaign showed that tobacco smoke is a trigger of asthma attacks in almost 80 per cent of people with asthma.[9]


One study has shown how exposure to cigarette smoke for just one hour caused a 20 per cent deterioration in the short-term lung function of adults with asthma.[10]


Up to a fifth of asthmatics continue to smoke8, and those who do have worse symptoms and lung function than non-smoking asthmatics.[11]


ā??Among teenagers, smoking increases problems from asthma and the respiratory function abnormalities associated with smoking are more marked in asthmaticsā? 11


http://www.ash.org.uk/html/passive/html/asthma.html