It's official: I've got tired hair. Too many parties in December, all that smoke, late nights and the piling on of hair products that comes with them have left my locks limp, not luscious; the colour I had done just a week or so ago has faded into a pale imitation of itself; and my curls are now frizzy rather than curly.

If, like mine, your hair is untreated, chances are that yours, too, will be feeling the weather badly, leaving it looking dull and grey. And if you've had your hair straightened, those same hazards - not to mention central heating and the temptation to over blow-dry when it's so cold outside - will have left it more at risk of breakage.

What better time to give your hair the attention it deserves by adding a leave-in conditioner to your hair-care regime. Leave-ins are much lighter than normal conditioners, and contain more moisture, which is why they are so effective. Applying a leave-in used to mean wearing a shower cap to bed, which is about as unsexy as you can get (covering yourself in heavy-duty night-time moisturiser is a close second), but these days they're much improved, and can even be worn during the day. What's more, they'll enhance your hairstyle, rather than making it look as if you've put mayonnaise on your head.

There are now two types of leave-in conditioner - spray and cream. "On curly hair, I'd use a heavy cream leave-in," says Desmond Murray, winner of the Hairdressers' Journal Afro Hairdresser Of The Year Award. "If the curls are very tight, a cream leave-in will tame your hair, eliminate frizz and take away some of the bulk, but only if you apply it when the hair is wet." Murray recommends conditioners from Nexxus and Paul Mitchell, but my personal favourite leave-in cream is All Soft Moist Ends by Redken.

Cream leave-ins are too heavy for straightened styles, however, so go for a spray, such as Bliss by Nioxin or So Long Heat Treat, from Redken. The latter is heat-activated, so is ideal for those welded to their blow-dryer. The sprays are also great for refreshing natural styles. But don't be tempted to use your normal conditioner as a leave-in, otherwise you'll end up with an itchy scalp and dry, crunchy hair, which kind of defeats the object.