Poisons advisers to the NHS have called for a new study into the safety of CS sprays used by the police. They said the sprays, issued to officers for self-defence, might be more harmful than has been assumed.

Their warnings, based on responses from medical staff to a survey conducted nearly six years ago, are published today in the Emergency Medicine Journal.

The Home Office said the findings on which the article was based had already been reviewed in 1999, and studies of the short and medium-term effects of the spray's use were difficult, as many of those sprayed were unlikely to cooperate.

But John Wadham, deputy chairman of the Police Complaints Commission, said: "Officers should be told about this valuable research and may need to be more careful in how CS spray is used. It is also time to re-evaluate other options, such as synthetic pepper spray, or examine whether the composition of CS spray can be changed to reduce damage."

The commission's predecessor body, the Police Complaints Authority, suggested in 2000 that the spray did not appear to present a serious risk, but its use where alcohol, drugs and mental illness might be involved "remains uncharted territory". It too called for better research into the effects of the spray.

Today's report, from the London unit of the National Poisons Information Service advising staff on the treatment and care of patients, is based on details of 152 cases of exposure to the spray.

The symptoms most often reported were burning sensations and blurred vision. But blistering, swelling and inflamed skin also occurred.

The Home Office said: "The cases referred to in this report must be taken in context with the number of times CS was actually used. Those presenting themselves for medical attention are likely to be a very small percentage of those sprayed during the period of the study."