Trichion: the hairline point in facial analysis
Quick facts
- Definition
- Point on the midline where the forehead meets the start of the hair.
- Role in the face
- Upper limit of the forehead and start of the upper third.
- Classic measurement
- From the trichion to the nasion: height of the upper third.
- Limitation
- Hard to define with baldness, a receding hairline or bangs; depends on context.
- Clinical use
- Helps describe forehead proportions and communicate the patient's concern.
The trichion is the midline reference point where the skin of the forehead meets the start of the hair. It defines the upper limit of the face in many proportion analyses and marks where the upper third begins. Together with the nasion, at the root of the nose, it forms the measure of forehead height.
Where does it fit in the proportions?
The classic analysis divides the face into three thirds of similar height: from the trichion to the glabella (or to the nasion), from the glabella to the base of the nose, and from the base of the nose to the chin. The trichion is therefore the starting point of the upper third. The division into thirds is a teaching model, not a requirement: real faces vary a lot, and many faces considered harmonious depart from these proportions.
| Point | Position | Marks the limit of |
|---|---|---|
| Trichion | Hairline on the midline | Start of the upper third |
| Nasion | Root of the nose | Reference for forehead height |
| Subnasale | Base of the nose | End of the middle third |
| Menton | Tip of the chin | End of the lower third |
What are the limitations of the measurement?
- Baldness and a receding hairline: the hairline has moved back, and the trichion has to be estimated.
- Bangs and hairstyle: they hide the point; asking for hair pulled back improves the reading.
- Hair surgery and transplants: they change the original reference.
- Curved forehead: the height measured from the front and the real one differ.
For this reason, the trichion should be used with care and as part of a broader assessment.
What the trichion does not tell you
Forehead height alone does not indicate that anything should be treated. Many patients have a high or low forehead and are happy with it. The conversation should start from the patient's concern. Lines, wrinkles and the mobility of the frontalis muscle are another matter, tied to toxin, and depend on individual assessment.
Talking with the patient
Avoid saying that the forehead is "too big" or that the hairline "is wrong". Use neutral descriptions and let the patient point out what bothers them. Aesthetic concerns related to baldness or the hairline call for referral to the appropriate specialty.
In Harmy
Harmy detects the face in the frontal photo and shows marking points for the treatable areas, including the Glabella. The app does not measure the trichion or forehead height, and the projection does not alter the hair, which the AI is instructed to preserve.
Also called: tr point, hairline limit.
Frequently asked questions
How do you define the trichion in someone with a receding hairline or baldness?
In these cases the point is hard to determine precisely. You can use the estimated original hairline, or set the measurement aside and assess the forehead as a whole, at the professional's discretion.