Expression Lines
What Are Expression Lines?
Expression lines are wrinkles that form on the skin as the facial muscles move when you smile, frown, and so on. When you are young, the wrinkles are temporary and disappear when your face is at rest, but when the movement of the facial muscles is repeated over many years, together with the loss of skin elasticity that comes with age, the wrinkles begin to remain even when the face is expressionless and become fixed. The areas prone to them include between the eyebrows, the corners of the eyes, the forehead, and around the mouth, but due to anatomical differences, how easily and how they appear differs by ethnicity, and of course the way wrinkles appear differs from person to person depending on face shape and habitual expressions.
Common Locations of Expression Lines
Horizontal forehead lines
Contraction of the frontalis muscle creates multiple horizontal lines on the forehead. Some people develop them because they have drooping eyelids (ptosis) and strain to open their upper eyelids.
Vertical frown lines (between the eyebrows)
These are the lines that form when you frown. Contraction of the corrugator and procerus muscles creates one or two lines between the eyebrows. Sometimes there are two on each side. With the involvement of the frontalis muscle, horizontal lines can also form above the brow. When the procerus muscle is strong, horizontal lines can accompany them below the brow (at the base of the nose).
Lines at the corners of the eyes (smile lines)
These are the radiating lines that form when you smile or squint. In English they are called crow’s feet. They are caused by contraction of the orbicularis oculi muscle, which runs in a doughnut shape around the eye.
Chin lines (pebble chin)
Overactivity of the mentalis muscle creates a crumpled, dimpled appearance on the chin. It is commonly seen in Asian people. It is more likely when the jaw is set back, small, or has poor dental alignment, and it can also develop as the jawbone atrophies with age.
Treatment of Expression Lines
Expression lines are treated with botulinum toxin injections. Botulinum toxin is a preparation containing type A botulinum toxin, a component produced by the bacterium Clostridium botulinum. In treating expression lines, it is injected into the muscles that create the wrinkles to suppress their contraction. BOTOX® was originally the product name of the U.S. company Allergan, but the name has spread and is used almost like a generic term.
Botulinum toxin injection
Botulinum toxin inhibits the release of a substance called acetylcholine from the motor nerves, blocking nerve transmission to the muscle fibers. When botulinum toxin is injected, the movement of the facial muscles that move the face is suppressed, so the muscles relax and the formation of wrinkles can be prevented.
The effect usually begins to appear two to three days after the procedure, reaches its maximum in two to four weeks, lasts about four to six months, and then gradually fades. Because the effect wears off, repeated injections are necessary.
It is best to begin treatment before the wrinkles become fixed, but even after some wrinkles have appeared, they often become shallower.
Side effects
Side effects of botulinum toxin occur when it also affects another muscle near the injection site. For example, when botulinum toxin is injected to treat vertical frown lines, the upper eyelid can droop, which is called ptosis. Also, for people who habitually raise their eyelids using the forehead muscles, injecting botulinum toxin for horizontal forehead lines can make the upper eyelids feel heavy. Furthermore, if it works more strongly on one side than the other, the expression can become asymmetrical. These side effects are temporary and disappear at the same time as the effect wears off. Summarizing the other side effects as well, they are as follows.
- Redness, swelling, pain, and bruising at the injection site
- Headache, discomfort, and unnatural facial expression
- Temporary symptoms such as drooping eyelids or brows, difficulty smiling, and difficulty moving the mouth
- Rarely, allergic reaction or infection
- Very rarely, systemic side effects (difficulty swallowing, difficulty breathing, generalized weakness, etc.)