J is for dislocated jaw, which can be brought about simply by yawning, or by a blow to the lower part of the face. A dislocated jaw is one that has become displaced from one or both of the joints that connect it to the base of the skull. This causes pain and means that the mouth cannot be fully closed. As a result, the victim has problems eating and speaking and may even find him or herself drooling.

The jaw is the most commonly dislocated joint because it is very unstable, and after dislocation has happened once, it tends to recur. The good news is that with the aid of someone else - preferably a trusted friend - the dislocation can be easily corrected. The helper should stand in front of the victim, place a thumb (wrapped in cloth to protect it when the teeth snap shut) on the lower back teeth at each side and press down firmly. The lower jaw should then click back into position.

K is for kiss of life which, given within three minutes of the heart or breathing stopping, can save a life and probably prevent brain damage. But a recent survey showed that faced with such an emergency, almost half the population would not know what to do.

To force air into the lungs, lift the victim's jaw and tilt the head backwards to open the airway, removing any debris from the mouth with the fingers. Pinch the nose firmly, take a deep breath, seal lips around the casualty's lips and blow into the mouth, until the chest rises; remove lips and allow chest to fall. Continue at about 10 breaths a minute, checking the pulse (on the carotid vein in the neck) every 10 breaths.

In babies, the lips should be sealed around the mouth and nose and gentle breaths exhaled once every three seconds. If the pulse is also absent, the kiss of life should be combined with chest compression to get the heart going. For details about first-aid courses, call St John Ambulance headquarters on 0171-235 5231.

L is for listeriosis, the disease of the Eighties, whose rise in incidence in Britain has probably been brought about by the growing popularity of French cheese and other goodies. Listeriosis is a flu-like illness caused by the bacterium Listeria monocytogenes, which is widespread in the environment, especially in soil. It can be found in soft cheeses such as Camembert and Brie, unpasteurised goat's cheese or dairy products, liver pate, pre-prepared salads including coleslaw, soft ice-cream and cook-chill meals.

In most adults, listeriosis only causes fever and aches and pains, and is treatable with antibiotics, but it can be life-threatening in the elderly and newborn. It can also cause miscarriage and stillbirth in pregnant women, who should avoid high-risk foods.