Many women report that their hair grows in thicker and fuller after losing it from chemotherapy.

Is this an illusion or is the hair shaft actually bigger in diameter?

Ask yourself why hair would truly grow in thicker and denser after the follicles were assaulted by poison.

I found no answers online to the question of “Why does hair come back thicker after chemo.”

So I asked a dermatologist with 37 years of clinical experience what could be the reason…

…but before I cover her explanation, I’d like to propose a very compelling theory…

The shorter one’s hair, the less daily “hair fall” there is.

Hair fall is caused by brushing, combing, washing, styling, running fingers through it, movement against a pillow, contact with hats, stress from wind, rubber bands and clips, etc.

  • If you have a crew cut, hair fall is greatly minimized because you can’t brush or comb a crew cut.
  • You can’t style it.
  • There is minimal stress to these very short hairs when you wash your hair.
  • Movement on a pillow is less stressful because the hairs aren’t long enough to be tugged or snagged.

If you maintain a crew cut, more hair will be solidly locked into its follicle at any given time.

Long locks have the potential for a greater amount of daily hair fall. Most women will tell you that their hair tends to look thinner or thin out when they let it grow long.

When hair comes back after chemo, it usually does not come back all at once.

However, by the time it’s buzz-cut or crew-cut length for many patients, all the follicles are reactivated.

All of them get a fresh start. They’re all in a growing phase at the same time. That means more hair.

But there’s something else: minimal hair fall due to the very short length of this regrowth.

  • It can’t be brushed or tied into a ponytail.
  • It’s too short to get blown around by the wind or snagged by clips and bobby pins.
  • Fingers don’t get run through it.

Thus, nearly all the hairs stay firmly in place. You have MORE hair growing at the same time, which is why it appears that it’s thicker than what it was prior to chemotherapy.

What a Dermatologist Says About Hair Growing in Thicker After Chemo

“Unfortunately, there is virtually nothing in the scientific literature to suggest or discuss an evidentiary basis for why this happens,” says Dr. Sharyn Laughlin, a dermatologist and developer of the DermaEnvy Skincare ™ line of sun protection products and medical director of Laserderm, a pioneering laser skin surgery clinic in Ottawa, Ontario, Canada.

Dr. Laughlin continues, “There are some investigations into the hair loss related to chemotherapy, including permanent alopecia.

“In reviewing some of those studies and looking for some crossover pathology, it’s clear that chemotherapy causes an inflammatory disruption to the hair follicle, including the bulb.

“The germinative areas of the follicle and bulge region that controls hair cycles can undergo what is called an ‘immune privilege loss,’ whereby your body begins to attack your own hair cells as a foreign body.

“Some miniaturization of the follicle can also happen, where the hair follicle becomes smaller and produces a finer or vellus type baby hair, as we see in other forms of baldness like male pattern baldness.

“This disruption has been specifically studied in permanent alopecia, but it’s conjecture to say how hair changes in color and texture might be similarly related.

“It is surprising that it has not garnered any more study in academic circles.

“Another speculation which I share with some of the sparse literature is that there could be an oncogenic mutation from the cancer involved, or it could be induced by the drugs themselves, with DNA changes that account for these disparate effects.

“It’s surprising that with chemotherapy, which should be damaging to the follicle, regrowth is followed by hair darkening, an increased hair diameter, and a change in structure seen as a curly texture.

“One final thought is that the immune suppressive and disruptive and inhibitory effects on cell mechanisms occur first.

“If the degenerative effect is non-lethal or not permanent, then there is a rebound effect to account for these changes as the follicle recovers.

“Clearly we have a limited understanding of the full phenomena. I suspect some form of DNA change must be occurring.

“It’s hard to definitively say what is involved but it would seem to be a fertile area, worthy of investigation.”

Certainly, hair growing in thicker after chemotherapy is nothing to complain about, but something to be fascinated by.

In practice for 30+ years, Dr. Laughlin has been lead or co-investigator in many research trials and an innovator in developing new laser technology.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.  


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