An investigation by BBC television's Watchdog Healthcheck programme, to be screened on Monday July 20, found that a range of big brand items which carried warning labels did not have any nut content at all.

Manufacturers have taken an overly cautious approach to avoid the possibility of litigation should a sufferer from nut allergy fall ill after eating one of their products.

There is concern that failure to identify a potentially harmful ingredient could lead to successful lawsuits.

Product testing

Watchdog Healthcheck sent five products carrying nut warnings for analysis:

• Kellogg's Frosties
• Mars Ice Cream
• Cadbury's Double Decker
• Marks and Spencer Syrup Sponge Pudding
• Tesco Stuck in the Mud Pudding

It is impossible to test for all types of nut but none of the products contained any trace of peanut protein, the most likely cause of a severe allergic reaction.

The products tested by Watchdog Healthcheck

The reason for the manufacturers' caution would seem to be based on the way they operate some food processing equipment with the same machinery being used to produce more than one type of product.

Even though the machinery is thoroughly cleaned between each batch, it is still possible that a few traces of nut may remain from one product to contaminate the next item on the line.

So, although the samples tested by Watchdog Healthcheck were peanut-free, it is possible another batch of items processed on the same machinery could be contaminated.

It is a risk that those with nut allergies must not take.

Kellogg's told the BBC that their quality control was "second to none" and that their procedures went beyond all statutory legal requirements.

But they felt that "due to an extremely small possibility that traces of peanut may enter the product chain, as a responsible manufacturer Kellogg's Frosties carry the label."

Violent reaction

The proportion of children affected by nut allergy has increased dramatically in recent years.

The allergy produces a violent reaction in sufferers when they eat nuts. It is known as anaphylaxis, and can be life threatening.

Sufferers may have difficulty swallowing or breathing because the allergic reaction produces rapid swelling wherever the nut comes into contact with the body.

Other symptoms can include vomiting, cramping stomach pains, diarrhoea, faintness and unconsciousness.

Anaphylactic shock can cause death due to obstruction to breathing or extreme low blood pressure.

The Chief Medical Officer Sir Kenneth Calman last month warned breast-feeding and pregnant women that eating peanuts could lead to their children developing a nut allergy.