1722: "Does Hair Grow Back Thicker if You Shave It?"

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Written By JC
1722: "Does Hair Grow Back Thicker if You Shave It?"
JC
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Interesting Things with JC #1722: "Does Hair Grow Back Thicker if You Shave It?"

Freshly shaved hair feels thicker because the razor leaves every strand with a blunt end instead of its natural tapered tip, creating the same illusion that has kept this myth alive for generations.

Curriculum - Episode Anchor

Episode Title: Does Hair Grow Back Thicker if You Shave It?
Episode Number: 1722
Host: JC
Audience: Grades 9–12, Introductory College, Homeschool, Lifelong Learners
Subject Area: Biology, Human Anatomy and Physiology, Scientific Inquiry

Lesson Overview

Objectives:

  • Explain how hair grows from follicles and distinguish between living and non-living parts of a hair.

  • Describe why shaved hair appears thicker even though shaving does not change hair growth.

  • Evaluate how scientific experiments can test common myths using evidence.

  • Apply biological concepts to distinguish observation from scientific fact.

Essential Question:
Why does shaved hair seem thicker if shaving does not actually change the hair follicle?

Success Criteria:

  • Students can explain the structure of a hair shaft and follicle.

  • Students can identify why blunt hair ends feel different from tapered ends.

  • Students can summarize the findings of historical scientific studies on shaving and hair growth.

  • Students can distinguish between perception and measurable biological change.

Student Relevance:
Many people hear or repeat the claim that shaving makes hair grow back thicker. Understanding why this myth persists helps students become more informed consumers of health information and demonstrates the importance of scientific evidence over anecdotal experience.

Real-World Connection:
Medical professionals, dermatologists, cosmetologists, barbers, and researchers rely on evidence-based knowledge of hair biology when advising patients and clients. This lesson demonstrates how science can answer everyday questions through controlled experimentation.

Workforce Reality:
Professionals in healthcare, dermatology, biomedical research, and cosmetology must separate long-standing beliefs from scientifically verified evidence. Critical thinking and evidence evaluation are essential workplace skills.

Key Vocabulary

  • Follicle(FAHL-ih-kuhl) – A structure beneath the skin where hair grows from living cells.

  • Hair Shaft(shaft) – The visible portion of the hair above the skin made of dead keratinized cells.

  • Keratin(KAIR-uh-tin) – A strong structural protein that makes up hair, nails, and the outer layer of skin.

  • Taper(TAY-per) – A gradual narrowing toward the natural tip of a hair.

  • Blunt End(blunt end) – The flat edge created when a hair is cut by a razor.

  • Coarseness(KORSS-ness) – The perceived thickness or roughness of a hair.

  • Diameter(dy-AM-uh-ter) – The measured width of a strand of hair.

  • Scientific Control(sy-en-TIF-ik kuhn-TROHL) – A comparison used in experiments to isolate the effect of one variable.

  • Perception(per-SEP-shun) – How something appears or feels, which may differ from measurable reality.

  • Hypothesis(hy-POTH-uh-sis) – A testable explanation or prediction investigated through scientific study.

Narrative Core

Open

Have you ever been told that shaving makes your hair grow back thicker? It's one of the most common pieces of advice people hear growing up, yet almost everyone who repeats it is mistaken. So why has this myth survived for generations?

Info

Hair feels different after shaving because the razor changes the shape of the hair that already exists—not the hair that grows next. A naturally grown hair tapers to a fine point, making it feel soft and appear thinner. Shaving slices through the shaft, leaving behind a flat, blunt end that feels rougher as it emerges from the skin.

Details

Hair growth begins beneath the skin inside follicles, where living cells divide and produce new hair. The razor never reaches these follicles. Since it only removes the dead hair shaft above the skin's surface, shaving cannot change the follicle's genetics or biological activity. Researchers began testing this belief nearly a century ago. Controlled studies, including one in 1928 and another in 1970, consistently demonstrated that shaving does not increase hair growth rate, thickness, weight, or coarseness. Modern research continues to support these findings. Newly growing hair may appear darker because it has not yet been lightened by sunlight, and the wider base of the hair is more visible than its naturally tapered tip.

Reflection

This myth illustrates an important lesson in science: our senses can sometimes mislead us. What feels true is not always biologically true. Careful experimentation allows scientists to distinguish perception from measurable fact.

Closing

A razor changes only the shape of the hair you cut. It never changes the follicle growing the next one.

These are interesting things, with JC.

Close-up of a person shaving one side of their face while the other side shows short beard stubble. Large text at the top reads, "Does Hair Grow Back Thicker if You Shave It?" with the series label "Interesting Things with JC #1722." The image illustrates the common myth that shaving changes hair growth.

Transcript

Interesting Things with JC #1722:

"Does Hair Grow Back Thicker if You Shave It?"

Fresh stubble feels thicker than the hair you just shaved off. That's the reason this myth has survived for generations.

It isn't because the hair changed. It's because the end of the hair did.

A strand of hair naturally tapers to a fine point. That narrow tip feels soft against your skin and makes the hair look finer. When you shave, the razor slices through the shaft, leaving a blunt, flat end. As the hair grows back, that cut end feels stiffer and looks wider than the original tip, even though it's the same strand.

That's also why a freshly shaved beard feels scratchy. You're touching hundreds of tiny blunt ends instead of naturally tapered hairs.

The razor never reaches the part of the hair that's alive. Hair grows from follicles beneath the skin, where living cells determine its thickness, color, texture, and rate of growth. Shaving only cuts the dead shaft above the surface, so it has no way to change the next hair the follicle produces.

The belief was already widespread by the early 1900s, so in 1928 researchers decided to test it instead of simply repeating it. Their work showed that shaving did not make hair grow faster. In 1970, another controlled study compared shaved and unshaved legs and found no differences in hair growth rate, diameter, weight, or coarseness. Decades of research since then have reached the same conclusion.

The illusion gets another boost because newly grown hair has not spent weeks or months exposed to sunlight, so it can appear slightly darker. The thicker base of the hair shaft is also more visible after shaving than the naturally tapered tip. If hair truly becomes thicker or coarser, the cause is usually hormones, genetics, aging, certain medications, or medical conditions that affect the follicle itself, not the razor.

Every hair that grows after you shave comes from the same follicle that produced the one before it. A razor changes the shape of the hair you cut. It never changes the follicle growing the next one.

These are interesting things, with JC.

Student Worksheet

Instructions: Listen to the podcast episode first. If audio is unavailable, read the transcript carefully. Complete all sections using evidence from the episode. Answer in complete sentences unless otherwise instructed.

Part A – Comprehension

  1. Why do freshly shaved hairs feel thicker than unshaved hairs?

  2. What is the difference between a naturally tapered hair tip and a shaved hair tip?

  3. Where does hair actually grow from?

  4. Why can't shaving change the thickness of future hair growth?

  5. What did scientific studies conducted in 1928 and 1970 conclude about shaving?

Part B – Analysis

  1. Explain why the myth that shaving makes hair grow back thicker has lasted for generations.

  2. Identify two observations people commonly make after shaving and explain the biological reason behind each observation.

  3. How does this episode demonstrate the importance of controlled scientific experiments?

Part C – Reflection

  1. Describe a belief or myth you have heard that could be tested scientifically.

  2. Why is it important to distinguish between personal experience and scientific evidence?

Difficulty Scaling

Level 1

  • Define "hair follicle."

  • Explain why shaved hair feels rough.

Level 2

  • Describe the relationship between the hair shaft and the follicle.

  • Summarize one scientific study mentioned in the episode.

Level 3

  • Explain how perception can differ from measurable biological reality.

  • Discuss why evidence-based thinking is important in medicine and everyday life.

Student Output Expectations

  • Complete sentences.

  • Support answers with evidence from the episode.

  • Use at least three vocabulary terms correctly.

Academic Integrity Guidance

  • Complete your own work.

  • Support answers using information from the podcast or transcript.

  • Distinguish clearly between evidence and personal opinion.

Teacher Guide

Quick Start

Begin class by asking students whether they have ever heard that shaving makes hair grow back thicker. Conduct an informal show of hands before revealing that scientists have tested this belief for nearly a century.

Pacing Guide (Audio-First)

  • Bell Ringer: 5 minutes

  • Podcast Listening: 5 minutes

  • Vocabulary Review: 5 minutes

  • Guided Discussion: 10 minutes

  • Student Worksheet: 20 minutes

  • Quiz: 10 minutes

  • Assessment/Exit Ticket: 10 minutes

Bell Ringer

Write on the board:

"Does shaving change the biology of your hair?"

Students write a brief prediction and explain why they think their answer is correct.

Audio Guidance

Students should listen once without taking notes.

During the second listening (or transcript review), students should identify:

  • Claims

  • Evidence

  • Scientific explanations

Audio Fallback

If audio is unavailable, students read the transcript aloud in small groups before beginning activities.

Time on Task

Approximately 60–70 minutes.

Materials

  • Podcast audio

  • Transcript

  • Student Worksheet

  • Quiz

  • Writing utensils or digital devices

Vocabulary Strategy

Introduce vocabulary before listening. Encourage students to identify each term as it appears during the episode.

Common Misconceptions

  • Hair grows from the visible shaft.

  • Hair is alive above the skin.

  • Razors affect hair follicles.

  • Scratchy hair is thicker hair.

  • Personal experience is always reliable scientific evidence.

Discussion Prompts

  1. Why can our senses sometimes mislead us?

  2. What makes a scientific experiment more trustworthy than anecdotal evidence?

  3. Why is repetition important in scientific research?

  4. How can myths continue even after scientific evidence disproves them?

Formative Checkpoints

  • Students correctly identify where hair grows.

  • Students explain the difference between the hair shaft and follicle.

  • Students distinguish observation from scientific measurement.

Differentiation

Support

  • Provide vocabulary cards.

  • Allow partner discussions.

  • Use guided note sheets.

Extension

  • Research another common biology myth and evaluate the available scientific evidence.

  • Compare myths that originated before controlled scientific testing became common.

Assessment Differentiation

Students may respond through:

  • Written responses

  • Oral presentation

  • Graphic organizer

  • Short video explanation

Time Flexibility

30-minute version:

  • Podcast

  • Discussion

  • Quiz

  • Exit Ticket

90-minute version:

  • Add research activity

  • Group presentations

  • Scientific literacy discussion

Substitute Readiness

This lesson is fully self-contained. The transcript provides all required instructional content if audio cannot be played.

Engagement Strategy

Conduct a class poll before and after the lesson to compare how student understanding changes after reviewing scientific evidence.

Cross-Curricular Connections

  • Biology

  • Human Anatomy

  • Health Science

  • Scientific Research

  • Critical Thinking

  • Media Literacy

SEL Connection

Students practice intellectual humility by recognizing that changing one's mind based on evidence is a strength rather than a weakness.

Skill Emphasis

  • Scientific reasoning

  • Evidence evaluation

  • Critical thinking

  • Reading informational text

  • Scientific communication

Answer Key

Worksheet

Part A

  1. The blunt end feels thicker.

  2. Natural hairs taper to fine points; shaved hairs have flat ends.

  3. Hair follicles beneath the skin.

  4. Razors never affect the living follicle.

  5. Shaving does not increase growth rate, thickness, weight, or coarseness.

Part B
(Expected responses should reference perception versus biology, experimental evidence, and controlled studies.)

Reflection
(Answers will vary but should distinguish evidence from opinion.)

Quiz

Multiple Choice

  • Why does shaved hair often feel rougher?

    • A. It becomes thicker.

    • B. It grows faster.

    • C. It has a blunt cut end.

    • D. It contains more keratin.

  • Where is the living portion of hair located?

    • A. Hair shaft

    • B. Hair tip

    • C. Follicle beneath the skin

    • D. Surface of the scalp

  • Which factor actually determines hair thickness?

    • A. Razor sharpness

    • B. Shampoo

    • C. Hair follicle biology

    • D. Frequency of shaving

  • Why might newly grown hair appear darker?

    • A. It contains more pigment after shaving.

    • B. It has not yet been lightened by sunlight.

    • C. It absorbs more moisture.

    • D. It grows more slowly.

  • What did controlled scientific studies conclude?

    • A. Hair doubles in thickness.

    • B. Hair grows twice as fast.

    • C. Shaving changes follicle genetics.

    • D. Shaving does not change hair growth characteristics.

(Answers intentionally omitted.)

Assessment

Open-Ended Questions

  1. Using evidence from the lesson, explain why shaving cannot change the biological properties of future hair growth.

  2. Explain how scientific experiments helped correct a belief that persisted for generations.

3–2–1 Rubric

3 – Proficient

  • Uses accurate scientific vocabulary.

  • Supports conclusions with evidence.

  • Demonstrates clear understanding.

2 – Developing

  • Mostly accurate explanation.

  • Some supporting evidence.

  • Minor misconceptions.

1 – Beginning

  • Limited understanding.

  • Minimal evidence.

  • Significant misconceptions remain.

Exit Ticket

In one or two sentences:

What is one scientific fact you learned today that changed or confirmed your thinking?

Standards Alignment

NGSS Science & Engineering Practices

Standard: SEP 4 – Analyzing and Interpreting Data
Connection: Students evaluate evidence from historical and modern scientific studies investigating the effects of shaving on hair growth.
Measurable Skill: Interpret scientific findings and compare conclusions from multiple investigations.
Justification: Students distinguish measurable biological evidence from commonly held beliefs.

Standard: SEP 6 – Constructing Explanations and Designing Solutions
Connection: Students explain why shaving cannot alter the biology of hair follicles.
Measurable Skill: Develop evidence-based scientific explanations using anatomical knowledge.
Justification: Reinforces the relationship between biological structure and function.

CCSS Reading

CCSS.ELA-LITERACY.RST.11-12.2 – Determine Central Ideas

Connection: Students identify the main scientific explanation presented in the podcast.

Measurable Skill: Summarize complex informational text while distinguishing supporting evidence from examples.

Justification: Strengthens comprehension of scientific communication.

CCSS.ELA-LITERACY.RST.9-10.4 – Vocabulary Acquisition

Connection: Students interpret domain-specific scientific terminology.

Measurable Skill: Correctly define and apply biology vocabulary in written responses.

Justification: Builds scientific literacy.

CCSS Writing

CCSS.ELA-LITERACY.WHST.9-10.2 – Informative Writing

Connection: Students explain biological concepts using evidence from the episode.

Measurable Skill: Produce organized, evidence-based scientific explanations.

Justification: Develops scientific writing skills.

CCSS Speaking & Listening

CCSS.ELA-LITERACY.SL.9-10.1 – Collaborative Discussion

Connection: Students discuss why scientific evidence is more reliable than anecdotal observations.

Measurable Skill: Participate respectfully while supporting ideas with evidence.

Justification: Encourages scientific discourse and critical listening.

C3 Framework

Dimension 3: Evaluating Sources and Using Evidence

Connection: Students compare personal observations with controlled experimental research.

Measurable Skill: Evaluate evidence before reaching conclusions.

Justification: Reinforces inquiry-based learning.

ISTE Standards for Students

ISTE 1.3 – Knowledge Constructor

Connection: Students gather information from the podcast and transcript to answer questions using credible evidence.

Measurable Skill: Evaluate information sources and synthesize factual conclusions.

Justification: Promotes responsible use of scientific information.

Career Readiness Competencies

Analytical Thinking

  • Evaluate claims using measurable evidence rather than assumptions.

Communication

  • Explain biological concepts using accurate scientific vocabulary.

Problem Solving

  • Identify the biological mechanism responsible for the appearance of thicker hair after shaving.

Adaptability

  • Revise previously held beliefs when presented with reliable scientific evidence.

Professional Judgment

  • Base conclusions on peer-reviewed research rather than anecdotal experience.

Homeschool / Lifelong Learning Alignment

Independent Learning

  • Investigate additional scientific myths using credible research methods.

Information Literacy

  • Differentiate between observation, opinion, and scientific evidence.

Real-World Application

  • Apply scientific reasoning to evaluate everyday health claims.

Self-Directed Inquiry

  • Develop questions that can be tested through controlled experimentation.

Transferable Life Skills

  • Use evidence-based reasoning when making health and personal care decisions.

Show Notes

Many people have heard that shaving makes hair grow back thicker, yet scientific research has consistently shown that this belief is a myth. This lesson explores the anatomy of hair, explains why shaved hair feels different, and demonstrates how controlled experiments help scientists separate perception from biological reality. Students strengthen their understanding of human biology while developing critical thinking and scientific literacy skills that apply far beyond this single question.

References

JC https://jimconnors.org
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