When it comes to tossing out your makeup, you should always look out for telltale signs for when these products have reached their expiration dates or if they’ve been infected by bacteria — causing more harm than help to your complexion. Some of these straightforward signs include:

COLOUR: Colour inconsistencies are a tell-tale sign. Ng says: “When a product loses its pigment, like when you dip a brush into a product and colour doesn’t get picked up, it’s a sign that the product has gone bad.”

SMELL: Lipsticks, foundations and lip glosses are most prone to changes in smells. So once you detect a change, the product has also been compromised.

TEXTURE: When you use a product and realise that the texture has changed, like if pressed powders don’t seem as smooth or worse, liquid formulations have started to separate, discard them immediately.

The experts agree that cleaning your makeup tools (brushes, sponges, puffs and Q-tips) is important to stave off the germs.

BRUSHES: Ng says if you use makeup daily, washing your brushes every seven to 10 days is the gold standard. “Wash the brushes with shampoo and lay them flat on a towel to dry,” she adds. She recommends baby shampoo instead of “the super nourishing ones” that add nutrients to natural fibres, instead of stripping them clean.

SPONGES/BLENDERS: Makeup artist Beno Lim prefers to use disposable ones. “This is safer and less likely to get contaminated after multiple uses.” Ng has another solution: Wash them after each use, then air dry completely.

POWDER PUFFS: According to Lim: “For loose powder puff, you may wash it once or twice. After that, it’s best to replace with a new one. Pressed powder puffs don’t hold their shape after washing and can also harbour germs in a closed compact. Get a new one instead.”

While you can keep your products as clean as possible, there are also small bad habits that need to go. Dr Alagappan advises keeping makeup out of the sun and bathroom: “Though it’s convenient, you should actually avoid keeping your makeup in the bathroom or next to the window. Humidity in bathrooms can promote bacterial growth, while direct sun exposure can affect the chemical composition in makeup and cause skin problems.”

Old habits like pumping the mascara brush into the tube also allow air and bacteria to get into the product. Lim warns: “When air is trapped inside the product, it shortens the lifespan of mascara.” Instead, swirl the brush around the tube before drawing it out, and wipe the bristles down with a clean tissue before putting it back in.

If all else fails, enlist the help of technology. Ng divulges her tip: Buy a UV sanitiser for home use. Turn it on to help sanitise your makeup, tools and brushes in between cleaning days.

LIQUID AND CREAM FORMULATIONS: Up to 12 months. Pump packaging for liquid foundation is the most hygienic as it will pump out just the quantity needed. You can also clean the nozzle with alcohol wipes.

POWDERS: Up to 2 years. Never use your fingers to apply any powder onto your face – instead, use a clean brush. For pressed powders, replace your powder puff regularly to reduce bacteria build-up.

EYELINERS AND BROW PENCILS: Up to a year. Sharpen them often to keep infected tips away.

MASCARAS: Up to 3 months. As it is used so close to the eyes, replacing mascara regularly helps to prevent eye infections. Do not share mascara, ever. It can spread bacteria from person to person.

LIQUID EYE MAKEUP: Up to 4 months. Do not use eyeliners and other liquid eye products beyond six months. They are used very close to the eyes, which can cause eye infections.

EYESHADOWS: Up to 18 months. However, keep a lookout after six months as it can cause reactions on the delicate skin around the eyes.

A version of this article first appeared in Her World