"Many people think that everything that comes out of a syringe is the same," says Melissa Kanchanapoomi Levin, MD, a dermatologist and founder of Entière Dermatology. 

There are two categories of injections: neuromodulators and fillers. Let's start with neuromodulators, known as botulinum toxin, often referred to by the brand name Botox. These interfere with nerve communication, effectively relaxing the muscles, to soften lines and wrinkles created by repetitive muscle movements.

While Botox isn't the only neuromodulator, it's also the OG—which, in fact, celebrates 20 years of FDA approval this month. (It's also the only neuromodulator approved by the FDA to treat health conditions such as chronic migraines and excessive sweating.) 

Fillers, meanwhile, do exactly what the name says. "Filler is a substance that fills a gap, unlike Botox, which goes into the muscles," says Dr. Obioha. While the exact substance in question can vary, the most common is hyaluronic acid. "We use fillers for many different reasons, whether it's to provide more structure to the cheekbones, to restore fullness to hollow areas under the eyes, or to fill any type of deep cracks or medium to deep lines around the mouth." , says Dr. Levin. It can also be used to add volume to the lips.

When should you start giving injections?

The "right" time to start these treatments depends largely on the individual.

Forget the rule "after the age of 30 you should think about Botox".

"If there is nothing to treat, then leave the face alone," says Dr. Kim.

A specialist you choose should assess this by looking at how expressive you can be, as this can determine whether you need neuromodulators.

"It's always better to do a little bit, then bring the patient back two or three months later and see how they look, reassess and come up with a different plan based on the first result," says Dr. Kim. "It's a transition, not a transformation."