💊 Chemotherapy-Induced Alopecia & Scalp Cooling Simulator

Anagen-Phase Hair Follicles

Follicle matrix cells divide fast, rivaling cancer cell turnover rates.

• ~90%: Follicles in anagen phase (scalp at any time)
• ~24-72h: Matrix cell cycle time (among fastest in body)
• 2-7 yrs: Anagen phase duration (active growth)
• ~0.35mm: Daily scalp hair growth (per follicle)

Why follicles divide so fast

Matrix cells rival tumor cells in division speed.

Fast division makes follicles collateral chemo targets.

Anatomy of the follicle

Bulb, matrix, dermal papilla, and shaft, briefly.

The hair growth cycle

Anagen growth, catagen transition, telogen rest phases.

Chemotherapy Circulation to the Scalp

Cytotoxic drugs travel systemically, unable to distinguish target cells.

• >80%: Alopecia risk, anthracyclines (without protection)
• >80%: Alopecia risk, taxanes (without protection)
• Bloodstream: Drug reaches scalp via (systemic circulation)
• Days: Onset after infusion (to first cycle)

Systemic, non-selective delivery

Blood carries drug everywhere, healthy tissue included.

Fast-dividing cells anywhere are vulnerable collateral targets.

Regimen-dependent severity

Different chemo classes carry different alopecia risk.

Why hair follicles are hit hard

High blood flow scalp region gets strong exposure.

Matrix Damage & Hair Shedding

Damaged matrix cells weaken the shaft, causing breakage and shedding.

• 2-3 wks: Shedding onset (after first cycle)
• Diffuse: Pattern (across whole scalp)
• Breakage: Shaft failure mode (not root loss)
• ~1-2 mo: Peak shedding window (during treatment)

Timeline of visible loss

Weakened shafts snap near the scalp surface.

Loss is typically abrupt, diffuse, and treatment-cycle linked.

Anagen effluvium mechanism

Growth-phase follicles are abruptly disrupted mid-cycle.

Regrowth after treatment

Follicles usually recover once chemo exposure ends.

Scalp Cooling & Vasoconstriction

Cooling caps chill the scalp, narrowing vessels feeding follicles.

• ~18-22°C: Scalp temp during cooling (target skin temperature)
• ~20-40%: Blood flow reduction (estimated local decrease)
• Pre/post infusion: Cooling duration (plus infusion time)
• ~1.5-3h: Cap contact time (per session typical)

Vasoconstriction mechanism

Cold narrows vessels, cutting local blood delivery.

Less blood flow means less chemo reaching follicles.

Reduced cellular uptake

Cooler tissue also slows drug metabolic uptake.

Device & protocol basics

Cap fitted snugly, cooled before, during, after dosing.

Hair Preservation Outcomes

Cooling gives partial-to-substantial hair preservation, not a guarantee.

• ~50-65%: Success rate (varies) (meaningful preservation)
• Regimen type: Effectiveness driver (drug class dependent)
• Risk reduction: Approach (not full prevention)
• Growing: Adoption (oncology centers worldwide)

Variable effectiveness

Outcomes differ by drug, dose, and individual patient.

Cooling shifts odds toward preservation, not certainty.

Patient experience factors

Cold tolerance and cap fit affect real-world use.

Weighing the tradeoff

Extra session time for a chance at preserved hair.