For its ability to cover up even the nastiest acne breakouts, and to make us look wide awake when we feel like death, concealer is a true make-up marvel.
But when it goes wrong? It can go really wrong.
Anna Vakili, a contestant on this year's Love Island, has taken a bit of a hammering on social media, thanks to her choice of under-eye make-up products.
"Anna, babe, blend out your under-eye concealer... and for the love of all make-up gods do not use that much ever again," was one of many comments on Twitter.
"Concealer can be our best friend," says make-up artist Frey-ja Barker. "However, if applied badly, it will not do us any favours."
So, whether you're a reality TV star or not, we've got the pro tips you need, from prepping your skin and choosing the right shade, to expert application.
Here are seven concealer fails and how to fix them...
"There are two elements that help concealer last longer throughout the day - primer and powder," says Marc Reagan, Hourglass global director of education, artistry and events.
"Our Veil Mineral Primer is our most popular product for a reason - it works on every skin type and skin tone and helps hold on to make-up, extending the wear all day. Apply a light layer all over the face or on areas where you typically find breakdown of make-up during the day."
Laura Hogsden, senior trend team make-up artist at Benefit, says eye cream is essential.
"Using an under-eye cream before make-up will plump the skin surface, helping to iron out fine lines and giving your under-eyes an even smoother and more radiant finish," she adds.
Your choice of concealer should depend on your skin concerns.
Barker says: "Concealers for breakouts tend to be a thicker consistency and I would advise looking for more of a matte finish, as you do not want to draw attention to it.
"A great formula to try would be Nars Soft Matte Complete Concealer, which comes in a little pot."
"As the skin under the eye is much thinner, opt for a cream concealer that is light in texture and highly pigmented, to hide dark circles whilst giving a smooth finish," Hogsden says. "Using an overly textured concealer will appear cakey and only enhance fine lines. Benefit Boi-ing Airbrush concealer would work perfectly for this, as it has a light texture and consistency."
"The Hourglass Vanish Seamless Finish Foundation Stick is super helpful when it comes to versatile coverage and portability," Reagan says. "It can be used as an all over primary foundation, or as a concealer to even skin tone or cover up a stubborn blemish."
Concerned about spots and dark circles?
"I think you cannot go too wrong with the famous Nars Creamy Radiant Concealer. Us make-up artists love it," says Barker.
"One of the biggest mistakes I see is people applying a much, much lighter colour than their natural skin tone. This can run the risk of looking grey or cloudy, especially in photographs," Barker says.
"To avoid this, try a colour corrector in a peachy tone for dark circles, followed by a light-reflecting concealer such as Charlotte Tilbury Magic Away Concealer."
For precise application, a flat brush is best, Reagan says: "When applying concealer, try to use a concealer brush, like our No 8 brush, for the most even coverage, and focus only on where you need it."
"I like to apply concealer under the eyes with a ponytail eyeshadow brush, such as Laura Mercier's," says Barker. "It allows you to buff the concealer without looking heavy or cakey."
When faced with purplish-black patches under your eyes, it can be tempting to slather on lots of product, but that's not a good idea.
"My advice is to always start with small amounts of product, because you can always layer more," Reagan advises.
"You want people to compliment you on your skin, not your concealer."
Barker says that, used sparingly, concealer can provide all the coverage you need, especially in summer when you don't want to wear a lot of foundation.
"Concentrate swiping in a cross formation through the face - a little in the centre of the forehead, down the nose, the apples of the cheek and chin, then blend," she says.
"A great concealer that is long-wearing in the summer months would be Tom Ford Emotionproof."
Conversely, if you're too heavy-handed you can end up wiping away the coverage altogether.
"Avoid blending or rubbing, or you'll only end up revealing the problem area again," Hogsden says.
"Patting the concealer will hold the coverage and pigment, and to ensure a seamless blend into our foundation you can use the warmth of your fingers to emulsify the concealer."
"Once the concealer is blended, it needs a powder to lock it in place," Reagan says.
"Gently stipple or press Hourglass Veil Setting Powder on top of the concealer, which will ensure the concealer stays in place and remains bright and radiant over the course of the entire day."