The Small Print Contact a Poison Control Centre "if more than used for brushing is accidentally swallowed" is the health warning on toothpaste labels in the US. One tube of toothpaste contains enough fluoride to kill a small child, says Dr Don MacAuley, chairman of Irish Dentists Opposing Fluoride (IDOF).

He points out that international research implicates fluoride in a wide range of health problems, including cancer, Alzheimer's, kidney damage, thyroid dysfunction, irritable bowel syndrome, arthritis and osteoporosis.

The Irish Fluoridation Forum, set up by the Department of Health, concluded "human health is not adversely affected" by the fluoride added to 71 per cent of the drinking water in the Republic and recommends that fluoride toothpaste is used in fluoridated and non-fluoridated areas.

"The idea that fluoride toothpaste is an innocuous product must be dispelled," says Dr MacAuley. "Fluoride is an enzyme inhibitor which disrupts the laying down of healthy bones."

The IDOF says fluoride is "a chemical which the Irish Medicines Board declares is not registered as a medicine, is unlicensed and has never been proved safe for effective use on humans".

It is accepted that children under seven are at risk of fluorosis - permanent white marks on the teeth and, in severe cases, brown staining and loss of teeth enamel.

The forum report states that water fluoridation has been "very effective in improving the oral health of the Irish population", but notes "the prevalence of dental fluorosis is increasing in Ireland".

IDOF estimates that 45 per cent of children and teenagers have fluorosis. In the UK, Colgate-Palmolive has paid compensation to parents whose 10-year-old son developed the condition, although the company did not accept liability.

To prevent children from swallowing fluoride toothpaste, the forum recommends: "Parents should supervise children aged two to seven years when brushing their teeth and should ensure that only a small, pea-sized amount of fluoride toothpaste is used."

One difficulty is that children under six or seven tend to swallow everything in their mouths as they have not developed a swallowing reflex, says Dr MacAuley, who believes they should not use fluoride toothpaste at all.

Other chemicals commonly added to toothpaste have been implicated in a range of health problems, from cancer to dermatitis. "Like many household products, toothpastes contain small quantities of substances that can be harmful if consumed in very large quantities," says Bernard McCartan, professor in oral medicine at the Dublin Dental Hospital. Sodium lauryl sulphate is used as a wetting agent and detergent in all kinds of product, from shampoos, bubble bath and shower gels to cleaner for garage floors and engines. A study reported in the American Journal of Toxicology found that SLS permeates the heart, liver, lungs and brains. It also reported that SLS irritates skin tissue, corrodes hair follicles and impairs the ability of hair to grow.

Prof McCartan says SLS can be an irritant in moderate concentrations. "Most people will not have any reaction to SLS but occasionally patients may develop local irritant reactions or mouth ulcers. These can be controlled by changing to a toothpaste that is SLS free," he says.

"An internet rumour in the 1990s suggested that SLS was a carcinogen. The International Agency for Research on Cancer \ maintains a database of probable and possible carcinogens. This list was last updated in July 2004 and does not mention SLS."

Triclosan, an anti-bacterial chemical also used in deodorants and soap, is a member of a family of carcinogens called chlorophenols. It is not, however, on the IARC database of carcinogens.

UK supermarket chains Asda, Sainsbury's, B&Q and Marks & Spencer are phasing out triclosan from their own-brand products by 2005, because it is suspected of leading to resistant "superbugs".

The Scientific Committee on Cosmetic Products and Non-Food Products intended for Consumers in 2002 concluded that triclosan is safe "taking into account the risk of resistance by certain micro-organism".

Propylene glycol is used in anti-freeze, deodorants and hair conditioners. According to a clinical review published by the American Academy of Dermatologists in 1991, it is a primary irritant to the skin, even in low concentrations, and is implicated in contact dermatitis, eye irritation, kidney damage and liver abnormalities.

However, the US Food and Drug Administration regards it as "generally safe" for food use and Prof McCartan comments: "While propylene glycol can cause allergic skin reactions, the lining of the mouth is often surprisingly resistant to such allergens and much higher concentrations can be tolerated than on the skin. There is no good evidence for a risk to health from propylene glycol in toothpastes."

Colours, aromas and artificial sweeteners such as saccharin and sorbitol - which have nothing to do with cleaning our teeth - are often added. Titanium dioxide, aka CI 77891, is a white pigment which has been found to cause tumours in experimental animals and has not been assessed for safety by the US Cosmetics Ingredient Review Board.

Toothpaste is viewed as a cosmetic and is not regulated, tested or licensed by the Irish Medicines Board because it does not make medical claims, says the IMB. It comes under Cosmetic Products Regulations, and responsibility rests with Environmental Health Officers and the Department of Heath and Children.

Prof McCartan believes there is a case to be made for stricter controls to be introduced on toothpaste but points out that the highly respected American Dental Association has evaluated many commercial brands.

Fluoride-free and chemical-free toothpastes are available in health food stores.

Typical ingredients of a tube of toothpaste

Aqua, Sorbitol, Hydrated Silica, Sodium Bicarbonate, Sodium Lauryl Sulphate, PEG-32, Aroma, Sodium Monofluorophosphate, Cellulose Gum, Hydroxyethyl-cellulose, Triclosan, Sodium Saccharin, Calcium, Glycerophosphate, CI 77891