If a black cat crosses your path then an allergy may soon follow

If a black cat crosses your path, you are likely to do more than just spit - the chances are you will scratch, sneeze orbreak out in a rash.

Far from bringing luck, black cats are likely to spark an allergic reaction, more likely than their white cousins, scientists have discovered. Allergy specialists found that patients who owned cats with dark hair were six times more likely to have an allergy illness than those with light-coloured pets.

For the study, reported at a conference on asthma and allergies, doctors compared people with mild and moderate allergic rhinitis, and those with no allergies.

"Patients were interviewed to find out their exposure to cats based on the colour of the pet, whether it was allowed in the bedroom and the animal's gender. The aim was to establish the correlation between the physical characteristics of cat hair and severity of allergic rhinitis,'' says a report on the research at Long Island College Hospital in Brooklyn.

Owners who had their cats in their bedrooms were no more likely to have an allergy than those who did not. The gender of the cat also made no difference to symptoms.

But the colour of the hair did, with 70 per cent of dark-haired cats causing problems, compared to fewer than 25 per cent of the light-coloured.

Why dark cats should have such an effect is not clear. One theory is that it may be connected to the thickness or composition of the hairs. It is known that animal dander - hair, skin scales, fur and feather - can cause both allergic reactions and asthma attacks, and the risk is higher with cats than dogs.