The philtrum is the distinct vertical groove located in the center of the face, extending from the base of the nose down to the upper lip. This anatomical feature, also known as the nasolabial distance, is a standard measurement in anthropometry, the study of human body dimensions. Measuring the philtrum’s length is a precise exercise in facial analysis, often used for research, cosmetic planning, and clinical evaluation. The objective is to determine the exact distance between two specific soft-tissue points, providing a fixed metric for a feature that varies significantly among individuals.
Defining the Anatomical Measurement Points
Accurate philtrum measurement relies on identifying two precise anatomical landmarks that serve as the start and end points.
The superior boundary point is the Subnasale (sn), the point where the nasal septum merges with the skin of the upper lip. This point is located directly beneath the center of the nose, marking the uppermost point of the philtrum’s groove.
The inferior boundary point is the Labiale Superius (ls), which is the most central point of the upper lip’s vermilion border. The Labiale Superius is specifically the midpoint of the Cupid’s bow, the double-curved contour in the center of the upper lip. Measuring the philtrum length involves finding the shortest straight-line distance between the Subnasale and the Labiale Superius.
Practical Step-by-Step Measurement Technique
To ensure the highest accuracy, philtrum length is ideally measured using a specialized tool like a sliding caliper, although a clear plastic ruler can be used for estimation. Before measurement, the subject must be positioned with their head in a neutral, relaxed posture, looking straight ahead, and with their mouth gently closed but not strained. This neutral facial expression is necessary because any movement, such as smiling or pouting, can alter the soft-tissue landmarks and skew the final reading.
The first step is to locate the Subnasale, placing one end of the measuring instrument at this point directly beneath the nasal septum. The instrument should be held perpendicular to the face, following the natural vertical line of the philtrum. Next, the other end of the caliper or ruler must be aligned precisely with the Labiale Superius, the center point of the upper lip’s vermilion border.
Care must be taken to ensure the instrument is aligned perfectly along the midline of the face. It must not press into the skin, which would compress the tissue and yield a falsely short measurement. Once the two points are located and the instrument is aligned, the reading is taken directly from the scale, typically recorded in millimeters. This process provides a quantitative metric for the nasolabial distance, allowing for objective comparison against established reference ranges.
Interpreting Philtrum Length and Clinical Significance
The measurement obtained is only meaningful when compared against normative data, which accounts for natural variations based on age, sex, and population. Philtrum length generally increases with age, which is why a shorter philtrum is often associated with a youthful facial appearance. Studies show that men tend to have a slightly longer philtrum than women, with average adult lengths typically falling in the range of 12 to 15 millimeters, though this varies widely across different ethnic groups and studies.
An unusually short or long philtrum can serve as a marker for certain underlying developmental or genetic conditions. For instance, a smooth philtrum, which often presents as a short philtrum, is one of the cardinal facial features used in the diagnosis of Fetal Alcohol Syndrome (FAS). In this context, the philtrum is not only short but also lacks the distinct vertical ridges and central groove that define a typical philtrum.
Other genetic conditions, such as DiGeorge syndrome or Cohen syndrome, may also feature a short philtrum. Conversely, a philtrum length that is significantly longer than the population mean can be an indicator in other specific syndromes. A single measurement does not constitute a medical diagnosis; rather, it is a piece of data that a healthcare professional may use alongside other clinical findings and a detailed medical history. If a person is concerned about their philtrum length, consulting a medical geneticist or a pediatrician is the appropriate next step for a professional evaluation.