“I start by looking at suggested shelf life and expiration dates for all opened and unopened items,” says New York-based beauty blogger Renee Chow. “It is a good indication of whether the product is usable or not, especially as beauty companies move towards more ‘natural’ formulas and different preservative systems.”

For products that do not have a suggested shelf life, Chow, aka Gothamista, suggests a more thorough examination.

“Any change in smell or colour is usually a sign that the product shouldn’t be used. For example, if a cream started off white and has turned brown or orange, it usually means it has oxidised [chemically reacted with oxygen],” she says.

“Separation also happens with products that are not made well or if the preservative system is no longer effective. The item could be susceptible to mould and should be tossed.”

You should also bear in mind that different items may last longer than others. Chow says oils such as marula and jojoba can stay fresh for a long time, while formulas containing volatile ingredients such as vitamin A, C, benzyl peroxide or retinol are best used as soon as they are opened. The same goes for sunscreen, which can become less effective with time.

When it comes to essentials, she suggests you stick to a cleanser, a hydrating product, a moisturiser and sunscreen. Items like masks and brush cleansers are more of a “luxury”.

According to Newby Hands, Net-a-Porter’s global beauty director, multitasking products are worth keeping, too.

When it comes to storage, keep all your skincare items stored in a cool, dark place – which doesn’t have to be the fridge. Contrary to popular belief, refrigeration does not guarantee that a product will stay fresh or last longer.

“After visiting many labs, I’ve learned that most formulas undergo stringent stability testing including exposure to sunlight, heat and cold. They can pretty much withstand anything,” Chow says.

Hair care

Unlike skincare items, haircare products can be kept much longer, says Andrea Clark, a certified trichologist (a hair thinning and scalp health specialist) and salon artistic director at The Mandarin Salon in Hong Kong’s Mandarin Oriental hotel.

“Items can be kept for three to four years if they are unopened, and generally are good for two to three years after opening. Most haircare products have a suggested shelf life but, rather than worry about the expiry date, I suggest trying them first to see if they’re effective,” she says.

Styling products like serums and hairspray tend to last longer than shampoos and conditioners, so these can be stocked up on.

“I would opt for a hair mask or heat protection spray/serum to give a layer of protection against heat, the elements, pollution and to smooth the [hair] cuticles,” Clark says, adding you should change your basic shampoo and conditioner according to the season.

Your styling tools – hairbrushes, combs and straighteners – are just as important as the products you use. These items tend to accumulate dust, grease and possibly bacteria, and should be cleaned frequently.

“Soak the brush or comb in warm soapy water, swish, rinse and lay on a towel to dry,” Clark says. “This method does not work with wooden items – they can go mouldy – so instead add a few drops of tea tree oil in a spray bottle filled with water, give them a spritz, then wipe clean. Straighteners should be wiped down with a damp cloth. Do not wrap the cord around the item as this could damage it over time.”

Make-up

“Most products feature a symbol that indicates when it is most useful and effective for a specified time period after the first initial use,” says Marc Reagan, director of global artistry, education and events at Hourglass Cosmetics.

“Many products lose their performance and efficacy after the indicated use-by date, and have a higher chance of harbouring bacteria if not cleaned and sanitised regularly.”

Lipsticks and powders such as blush and eyeshadow have the longest lifespan – around two years, Reagan says. Foundation, concealers and liners can last between six months to a year, while mascara should be replaced every three to six months.

“Storing your make-up in a cool, dry place is always going to extend the lifespan of a product to its full potential. Extreme temperatures are never good for any make-up, so try to put less frequently used items in containers that are kept out of direct sunlight to maintain the efficacy of the products,” he says.

For women choosing more simplified routines while working from home, Reagan suggests an edited collection of products that includes concealer, face powder, blush, an eyebrow pencil and mascara. Tools can also be kept to a minimum – many make-up artists like to use their fingers instead – although brushes should be washed at least once a month.

“Make sure to use a gentle shampoo or brush cleanser to remove all make-up residue and build-up, and lay them flat to dry,” Reagan says. “Once completely dried, store your brushes in a pouch or container that is at least the length of your longest brush so that the bristles are not bent or misshapen.”