The biology of the bulb

The root of the matter

Hair grows from a structure called the hair follicle — a tiny pocket beneath the skin's surface where a cluster of cells called the bulb produces the hair shaft. The bulb is fed by a blood vessel and governed by a growth cycle that every hair on your body follows.

Intense Pulsed Light (IPL) works by targeting the melanin — the pigment — inside the hair shaft. When a pulse of broad-spectrum light is absorbed by that pigment, it converts to heat. That heat travels down the shaft and into the bulb, raising it to a temperature that disables the follicle's ability to produce a new hair.

Why the follicle matters

Unlike shaving, which only cuts hair at the surface, or depilatory creams that dissolve the shaft, IPL addresses the source. A disabled follicle either stops producing hair entirely or produces a finer, lighter hair that is barely visible. Over a full treatment cycle, the density of regrowth diminishes session by session.

This is why IPL is described as a long-term approach rather than a quick fix — it changes the conditions under the skin, not just the hair above it.

The growth cycle

Every hair moves through three phases:

• Anagen — the active growth phase. The bulb is attached to the blood supply and the hair is growing. This is the only phase in which IPL is effective, because the bulb is present and pigmented.
• Catagen — a brief transitional phase. The follicle detaches from the blood supply.
• Telogen — the resting phase. The old hair sits in the follicle until a new anagen cycle pushes it out.

At any given time, roughly 20–30% of your body hair is in the anagen phase. That's why a single session never clears an area — the dormant follicles wake up later and need to be caught in a subsequent session.

What your skin does between sessions

The weeks between treatments are not idle. Your skin is quietly cycling follicles through their phases, shedding treated hairs, and resetting. Treated hairs often don't fall out immediately — they work their way to the surface and release over 1–2 weeks.

This is why consistency matters more than intensity. A gentle, regular cadence catches each wave of follicles as they enter anagen, while giving your skin time to recover between passes.

The takeaway

IPL isn't magic — it's biology. By understanding the follicle, the growth cycle, and the role of melanin, you can set realistic expectations: gradual, cumulative reduction over weeks, not overnight erasure. The patience is the point.