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If the only thing you know about filler is that Kylie Jenner was open about it in her lips, consider this your cheat sheet on one of the most-talked-about facial procedures of 2017. From what’s inside them to how long they last to where they can go in your face, this roundup is packed with pro secrets on ingredients, side-effects, wrinkles, and more and will clear up all your confusion and maybe even misconceptions.

1. They’re Not Always Permanent

If you’re afraid they’ll last forever, you might consider this a good thing. If you don’t like the cost of upkeep, well, the permanence that fillers provide might be a slight disappointment. How long the results last also depend on what type of filler you get, its ingredients, where it’s injected, and the individual. For example, JUVÉDERM Volbella XC, a subtle treatment for the lips, can last up to a year, while Vollure, commonly used on the nasal labial folds, can last up to 18 months. Restylane claims its lip treatment last about six months as well.

With that being said, you don’t have to continue doing it over time once you start. “Patients think that once you do it that you have to keep doing it,” explains Dr. Kimberly J. Butterwick, a dermatologist based in San Diego, California. "You could have facial fillers once in the cheeks or nasal labial folds and decide you only want to do it for this wedding, and when it wears off, you’re back to your baseline. You’re no worse for having tried it. You don’t have to keep doing it if you don’t want to,” she says.

2. They’re Used All Over the Face

There are different versions of fillers created to treat several areas of the face. Common places that get injected? Cheeks, lips, and nasal labial folds around the mouth. What product is used depends greatly on factors like the depth of your wrinkles and the intensity of the look you’re going for.

3. If Your Wrinkles Are Super Deep, Fillers Won’t Make Them Disappear

"They certainly may be too deep to make fully go away with filler, but the appearance of wrinkles can always be improved,” explains board-certified cosmetic dermatologist Dr. Kenneth Mark. "In cases like this, it is very important to manage expectations, and patients need to realize if the wrinkles are super deep they may require a greater number of syringes and/or treatments of filler.” If laxity, or very loose skin, is the problem, Dr. Butterwick says more of a lifting procedure might be needed.

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4. Botox and Fillers Are Completely Different

Dr. Butterwick says this is one of the biggest misconceptions she hears at her practice. "They will point to their lips and say, 'I want to put Botox in my lips to fill it,' so they confuse those two issues when they are completely different and have different uses,” says Dr. Butterwick. “Botox works for muscle movement, for wrinkles that are primarily caused by intense facial expression. They relax the muscle, so in-between the eyes, that frown line, that’s the perfect place for Botox because those wrinkles are caused by the muscle movement over and over, and the crow’s feet area. In the mouth area, you can put a little bit of Botox just to reduce excessive muscle movement, but it’s not really for wrinkles because we need to have all the muscles around our mouth for natural expression and eating and talking. One is used for filling and correcting and one is used for excess muscle movement.”

5. They Can Be Reversible
Don’t like the look? Suddenly changed your mind and you want it gone ASAP? You don’t have to be in a sticky situation for a year because fillers made of hyaluronic acid are reversible. “Say you didn’t like it or you had a little problem with it, you can take an enzyme and dissolve it easily,” says Dr. Butterwick. Of course, this is something that is administered by a professional.

6. Where and How They’re Injected Will Change as You Age

Injections are extremely personal and many professionals will make the decisions on where to place them based on your face shape, as well as your desired result. "The biggest misconception that I see about fillers is everybody thinking, doctors and patients alike, that it's a 'one look fits all,'" says Dr. Mark. He mentions that pros should approach each patient "like an artist" to truly customize the treatment.

And where they're placed also is determined as you age because your face changes shape through the years. "The face is changing throughout our lives, so at age 25, you might need a little enhancement of the cheekbones or the lips, but by age 65, you need more correction of volume loss," explains Dr. Butterwick. "Needs change throughout each generation, so that's why you don't want permanent filler because what looks good when you're 30... it would be in the wrong place by 50."

7. There Are Potential Risks

The most minor risks include bruising, but Dr. Butterwick says that you could experience lumps or bumps or asymmetries if the injector isn’t used to injecting filler in a smooth manner. The most serious and dangerous risk, however, is when filler is injected into a blood vessel. “Sometimes if there’s a lot of pressure on the syringe and it’s put in too quickly, it could flow backwards and get into an artery, and the artery supplies oxygen to the tissue. So you can block the oxygen and get what we call necrosis of the skin,” she explains. "Patients have come who have had filler elsewhere and get an area breakdown of the skin.”

Dr. Butterwick says that it can be reversed without any consequence if it’s treated with the dissolver immediately. Another dangerous yet very uncommon risk is blindness when injecting around the eyes or nose. “There’s a remote chance of injecting it into an artery that communicates with the vasculature around the eye, and it can rarely, rarely lead to blindness." This is why you should always visit an experienced cosmetic dermatologist to be safe.

8. Many Are Made with Hyaluronic Acid

Yep, as in the same ingredient that’s in so many of your favorite moisturizers. "My favorite fillers today are made of hyaluronic acid, which our bodies are used to in the sense that it is in our skin and joints,” says Dr. Mark of this naturally-occurring substance, which he prefers instead of fillers with “foreign body type substances.” JUVÉDERM fillers are example of hyaluronic acid-based formulas.

Found in your skin but reducing in count as we age, Dr. Butterwick explains that 40 perfect of your dermis is actually composed of hyaluronic acid, and because it’s a non-animal product and so highly purified, you have an unlikely chance of allergic reactions. And of course, it’s dissolvable.

One of them is especially for the lips, patients think that it automatically looks unnatural,” says Dr. Butterwick. “They don’t realize that fillers can be put into the lip and you get that really natural, subtle correction, so a lot of people think that fillers naturally mean one of those super overdone faces that we see sometimes.”