Have you ever considered that your make-up could be bad for you?

If you've suffered from sore, itchy and watery eyes, your make-up could be responsible. According to a recent survey, one in four women put their health, and looks, at risk by using out-of-date beauty products.

The College of Optometrists found that despite spending a fortune on make-up, many women don't consider the hygiene issues associated with the products they use.

We all know that mascara doesn't last forever, but many of us only throw make-up away when it's empty or stops working, not when it's full of bacteria. A massive 92 per cent of women surveyed admitted to keeping their mascara for longer than six months, and nearly two-thirds said they used eye make-up that was more than two years old.

Sharing make-up with friends is another big no-no, and can lead to passing on eye infections.

So what is so wrong about aging mascaras? Dr Susan Blakeney, an advisor to the College of Optometrists, tells us: "Mascara can be a breeding ground for bacteria, so it's not surprising we've found that nearly half of women suffer from itchy, watery and red eyes when they're holding onto their make-up for so long and sharing it among friends.

"The irony is that eye infections are not a pretty sight!"

Susan explains: "Most women are either unaware of or simply ignoring the manufacturers' recommended use-by dates."

So how long is it okay to keep make-up? The shelf life or use-by date of products varies. EU regulations mean that all packaging should indicate how long it's acceptable to use the product for. The problem is that there are no regulations as to how manufacturers come up with shelf life figures, hence the information you're given is patchy.

Most beauty products and make-up will contain preservatives - so if you haven't opened them, they're likely to last a long time. However, once they've been opened, they'll start to deteriorate and breed bacteria.

Most women don't need an excuse to buy more make-up, so read our guidelines to get an idea of when you should bin your products, then hits the shops to stock up on more.

Mascara

Keep it for just three to six months. Stick to one mascara at a time and you'll use it up before it becomes a health hazard. And remember, one mascara for one person - never share products.

Moisturizer

The shelf life of moisturizer is between three and 12 months. Using a clean spatula rather than your fingers will reduce the likelihood of bacteria getting into the pot. If it changes smell or colour, throw it away.

Foundation

Foundation should keep for between 12 to 18 months. Wash application sponges or brushes with warm soapy water at least weekly, preferably daily. Choose products that come with a pump: this way the product get little exposure to the air, so it stays fresher for longer.

Powder

A pressed powder should last for two years, though a loose powder could last for three years. Again, wash any brushes or sponges at least weekly.

Concealer

Treat concealer like you would foundation: it should last for 12 to 18 months. Avoid any product with an applicator that has to touch the skin; it'll instantly become a breeding ground for bacteria.

Blusher

A powder blusher will last for two years, but wash brushes regularly. Cream blushers can start to deteriorate after about 18 months; if they change colour or consistency, chuck them out.

Eyeshadows

Like blusher, cream eyeshadows are good for about 18 months, whereas powders can last for two years. Wash all brushes, and if you have to apply products with your fingers, make sure you've just washed your hands.

Eyeliner and lipliner

Pencil liners are useful as sharpening them removes any bacteria they may have picked up. As long as this is the case, they should last for up to two years.

Lipsticks and lipglosses

Lipsticks can last for two years but lipgloss is generally only good for around 18 months. Never use any lip product if you have a cold sore; if you do, throw it out. If the product looks like it has changed colour it's time to get rid of it. Again, if you use a brush, wash it regularly.

Make-up dangers

Now we know when to bin make-up, but the risks from make-up don't stop with bacteria. Are you aware of the top five make-up dangers?

1) Don't apply make-up on the move. Who hasn't applied mascara on the bus? Or touched up their eyeliner on the train? Applying make-up while on the move is the cause of the most common make-up related injury: wobbly hands lead to mascara wands or eyeliners scratching the eye.

2) Don't share your make-up. If you're sharing your make-up, you're sharing your bacteria. This applies most to mascara, eyeliner and lipstick.

3) Don't apply make-up to the inside of your eyelids. It might look cool in a slightly gothic kind of way, but it can block glands and lead to dry eyes and styes.

4) Put contact lenses in before you apply make-up. Not only does this mean you can actually see what you're doing, but you're also less likely to get make-up under your lenses.

5) Don't use shop product samples on your face. Stop for a minute and consider how many people have stuck their fingers into that eye shadow. Now do you want to put it on your face?