Detailed Explanation of Hair Pull Test
The hair pull test (also known as traction test or trichogram) is a simple method to assess hair loss patterns or scalp health by gently pulling the hair. It is commonly used for home self-testing or as an auxiliary clinical diagnostic tool.
1. Principle and Purpose
Principle: By applying external force to hair in the telogen phase or abnormal states, the number of shed hairs is observed to evaluate follicular health.
Purpose: To preliminarily identify types of hair loss (e.g., telogen effluvium, androgenetic alopecia, alopecia areata) or scalp inflammation.
2. Experimental Procedure
Preparation Phase
Timing: Conduct 24–48 hours after shampooing to avoid interference from natural shedding during washing.
Hair Condition: Ensure hair is dry and free from styling products (e.g., hair gel, wax).
Operation Steps
Sampling: Pinch a strand of hair (~50–60 strands) between thumb and index finger, sliding slowly from root to tip.
Force Control: Apply uniform force (~1 Newton) to avoid false positives due to excessive pulling.
Result Recording
Normal Range: ≤3 shed hairs (physiological shedding).
Abnormal Cases: ≥6 shed hairs suggest active hair loss, requiring further examination.
3. Result Interpretation and Precautions
Positive Result (≥6 shed hairs): May indicate telogen effluvium, alopecia areata, or scalp inflammation.
Negative Result (≤3 shed hairs): Typically normal metabolism, but should be assessed alongside other symptoms (e.g., hair texture changes, scalp itching).
Precautions:
Repeat testing for 3–5 days to avoid single-test errors.
If accompanied by scalp redness, pain, or persistent hair loss, consult a doctor to rule out fungal infections or autoimmune diseases.
4. Limitations of the Test
Cannot differentiate hair loss types (e.g., androgenetic alopecia vs. alopecia areata).
Requires confirmation via professional methods like dermatoscopy or hormone testing.
5. Related Research and Applications
Clinical Studies: A negative pull test result can serve as evidence for the efficacy of hair regeneration treatments (e.g., PRP therapy).
Material Science Experiments: Hair exhibits high tensile strength—a single strand can withstand ~0.88N of force, while 100,000 strands can bear 5 tons.
The ST-16AS Hair Friction and Tensile Tester evaluates hair characteristics—such as friction and tensile force—by mechanically moving a toothed comb to simulate hair brushing.
The instrument comprises:
A texture analyzer (standalone version) with dedicated software
Spare probes and accessories
Its core structure includes:
A mechanical device that induces deformation on samples
A container for holding test specimens
A recording system capturing force, time, and deformation rate
Testing focuses on three parameters—distance, time, and applied force—with results analyzed for mechanical texture properties. The analyzer offers high sensitivity and objectivity, allowing precise quantitative processing via specialized software to generate standardized evaluation metrics.
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