As mentioned before, Botox is not just a treatment to reduce existing wrinkles.

Many people receive it to prevent wrinkles from deepening over time.

 

Among the commonly treated areas, the forehead is one of the most popular.

However, some people experience:

“After the injection, my eyes feel heavy.”
“My brows look strange, like a samurai eyebrow.”

 

Let’s break down why these side effects happen
and how they can be prevented.

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1. What causes these side effects?

The forehead muscle (frontalis) not only creates forehead lines.

It also helps lift the eyelids when you open your eyes.

 

If your eyelids are naturally heavy, or if aging has caused them to descend,
you may unconsciously recruit the forehead to help lift your eyes.

 

If Botox weakens this muscle too much—especially the portion involved in lifting—
you may experience:

• Heaviness
• Half-open, tired-looking eyes
• Droopy appearance

 

These effects often occur when injections are placed too low,
in the area close to the eyebrows
(lower one-third of the forehead).

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2. Everyone’s forehead muscle shape is different

 

Anatomy books show the frontalis as one wide sheet,
but in real people, the shape, width, and activation pattern vary greatly.

 

Examples:

• Some people use mainly the central portion
• Some activate both the center and outer portions
• Some hardly use the forehead at all, relying more on peri-orbital muscles

 

Therefore, injections should never follow a fixed diagram.

 

The first step is always:

“Please open your eyes as wide as you can.”

 

By observing where the movement begins and how far it spreads,
the physician identifies your unique muscle pattern.

This greatly reduces the risk of side effects.

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3. Why must we avoid the lower one-third of the forehead?

The lower one-third, close to the eyebrows,
is the zone most involved in eyelid elevation.

 

If this area is weakened too aggressively:

• The eyelids may appear more droopy
• You may look tired or older
• Lifting effort decreases

 

For this reason, practitioners typically inject
above the lower one-third,
avoiding too much product near the brows.

 

Small positional differences can create big differences in outcome.

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4. Why divide injections into at least six points?

 

A key principle:

It’s not the total dose, but how finely it’s divided.

 

If the same dose is injected into only 2–3 large points:

• One area may become excessively weakened
• The result may look uneven or unnatural

 

When the same dose is split into six or more smaller points,
muscle relaxation is smoother and more even,
and facial expressions remain natural.

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5. Why do “samurai brows” happen?

“Samurai brows” refer to brows that flare upward on the outer ends.

 

This happens when:

• The outer portion is not properly controlled
• The inner/central portion—where most strength exists—is under-treated

 

The frontalis does not extend very far laterally.
Most functional contraction occurs centrally to slightly medial.

 

If injections are placed only high and lateral,
while missing the true active zone,
the outer brow may overcompensate and rise.

 

Correct placement requires checking:

• How far the frontalis actually extends
• Its distance from the brows
• The vertical level of the active zone

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6. Ultimately, it is a design and assessment issue

 

To minimize forehead Botox complications,
three core principles apply:

 

① Avoid aggressive treatment of the lower one-third

Preserves eyelid-lifting function.

 

② Divide the dose into at least six small injections

Allows gradual, even weakening without harsh borders.

 

③ Assess individual muscle patterns before injecting

A simple “open your eyes wide” test reveals the correct pattern.

 

These steps cannot guarantee zero side effects,
but they dramatically reduce:

• Heaviness
• Droopy lids
• Unnatural brow shapes

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7. Final advice

Successful forehead Botox depends more on:

“How the physician evaluates and adjusts the treatment area”

than on
“How many units you receive.”

 

When consulting, consider asking:

• How do you evaluate my muscle pattern?
• How do you determine injection depth and placement?
• How will you avoid eyelid drooping or brow distortion?

 

Everyone’s forehead shape, eyelid anatomy,
and muscle usage habits differ.

Therefore, the correct dose and pattern must be personalized.

 

Accurate diagnosis and treatment planning should always be done
in a face-to-face consultation with a qualified medical professional.

 

📍 Primi Clinic
52 Seongsuil-ro, Seongdong-gu, Seoul, 3F (Primi Clinic)

 

📍 Primi Clinic
서울특별시 성동구 성수일로 52 3F

Forehead Botox Side Effects — Why Do Eyelid Drooping and Uneven Brows Happen?