You reported that a consultant occupational physician at Blackpool Victoria Hospital trust had noticed two asthmatic workers suddenly got worse after the trust installed automatic air fresheners ('Taking the air', news focus, page 16, 2 August). A spokesman said they were unaware of reports linking air fresheners to ill-health.

There is such evidence, but the problems are not limited to asthma and rhinitis. Very low exposures to volatile organic chemicals (VOCs) were noted to cause symptoms in some people as long ago as the 1950s, and specific observations about air fresheners first appeared in 1985. Air freshener use increases the level of VOCs in air.

The provocation of symptoms by VOCs (especially scented chemicals or those designed to interfere with smell recognition) is confirmed daily by doctors who look for environmental triggers. The condition, multiple chemical sensitivity (MCS), gets worse if exposure continues, and sensitivity often spreads to other chemicals. The most seriously affected have great difficulty living a normal life and finding a work environment they can tolerate.

Even without air fresheners, hospitals are difficult places for very sensitive patients because of pollens, perfumed toiletries, solvents, cleaning chemicals and other VOCs. Some patients admitted as emergencies have had to be discharged as soon as they were stabilised because they were badly affected by the air pollution in the hospital. While I was taking an allergy clinic at Airedale General Hospital, some of my MCS patients had to wait outdoors, were unwell and found concentration difficult during the consultation.

For many years I was involved with the Airedale allergy centre, an environmentally controlled inpatient unit. Most patients there had experienced symptoms for many years, some extremely disabling, which conventional management had failed to relieve. When patients fasted in this 'clean' environment, most of their symptoms were relieved within a few days. Reactions to volatile organic chemicals were common.

The NHS needs to consider MCS seriously. If all staff are to work at maximum efficiency, every effort should be made to keep VOC levels as low as possible. US studies suggest multiple chemical sensitivity may affect 16 to 36 per cent of the population, varying from minor inconvenience to severe bronchospasm. Effects on concentration and memory are common, and even minor disturbances could have serious consequences if they affected a quarter of staff.

MCS patients usually develop symptoms in a number of systems, resulting in referrals to different consultants, causing a considerable burden on the NHS. It is ironic that just as the effects of MCS are becoming recognised, some public services are increasing the risk of people becoming sensitised, with proposals to perfume the London Underground and sell perfumed stamps.

The NHS is overworked enough without the increased burden of unnecessary MCS.

Dr Honor Anthony Environmental allergist Leeds