Why Isn't Scalp Injection for Hair Loss a One-and-Done Treatment? Learn About Its Effects and Treatment Frequency | Daechi-dong Hair Loss Clinic

Hello, I am Dr. Dajeong Kim, the chief physician of Cordia Clinic.

Many people considering scalp injections for hair loss often have the following questions.

“Will my hair grow if I only get the injection once?”

“Why do I need multiple treatments?” or “Do I have to keep getting injections for the rest of my life?”

To answer briefly, a single scalp injection can trigger a biological response, but it takes time to see changes in hair thickness and density.

In addition, male and female pattern hair loss can progress over time, so follow-up observation and ongoing management may be needed even after treatment.

Today, we will look at why scalp injection treatments are repeated and when it is appropriate to evaluate their effects.

1. Hair Does Not Grow Overnight

Hair goes through repeating cycles of growth (anagen), regression (catagen), and rest (telogen).

Even on a healthy scalp, each hair follicle has its own growth cycle, and hair grows about 1 cm per month on average.

In male and female pattern hair loss, follicles gradually shrink, a process known as ‘follicular miniaturization.’

During this process, the anagen (growth) phase becomes shorter, and thick hairs gradually become thinner.

Scalp injection treatments aim to influence the growth environment of the follicles and encourage changes that favor hair growth.

However, the point at which changes begin in the follicles is different from the point at which hair actually looks fuller.

Therefore, even if no noticeable change appears right after treatment, it is difficult to conclude that the treatment is ineffective.

2. What Ingredients Are Used in Scalp Injections?

Recently, various injectable treatments aimed at improving the environment around hair follicles and promoting hair growth have been studied.

① Botulinum Toxin

Botulinum toxin is being studied mainly for its effects on scalp muscle tension and the environment around hair follicles.

A meta-analysis published in Dermatologic Surgery in 2025 pooled eight studies and reported that the botulinum toxin treatment group showed a significant increase in hair count compared with the control group.

This suggests that scalp Botox may have potential as an adjunctive treatment for hair loss.

② PDRN

PDRN is a substance involved in tissue repair, blood vessel formation, and regulation of inflammatory responses.

Its potential to affect hair growth by improving the environment around hair follicles is being studied.

Positive results related to improvements in hair density and thickness have also been reported in small clinical studies involving patients with female pattern hair loss.

③ Exosomes

Exosomes are a type of extracellular vesicle that transmits signals between cells.

Their potential to influence the activity of dermal papilla cells and hair growth-related signaling pathways is being studied.

A systematic review published in 2025 also observed improvements in hair density and thickness in some human studies. For reference, exosome injections have not been approved for use in Korea.

However, these treatments are still supported by limited research, and because formulations and procedures vary widely, further studies are needed to establish standardized treatment frequencies and long-term effects.

3. Why Are Scalp Injections Given Multiple Times?

There are two main reasons why scalp injection treatments are repeated.

First, hair growth takes time.

Even if biological changes occur around the follicles after an injection, new hair must go through several growth stages before it fully develops.

Second, male and female pattern hair loss is a condition that can continue to progress.

Follicular miniaturization driven by genetic predisposition and hormones is unlikely to be permanently halted by a single injection treatment.

For this reason, some treatments involve repeated procedures to monitor changes, with additional sessions given as needed.

However, repeating injections does not always produce greater results, and the same number of treatments cannot be applied to every ingredient.

4. How Many Scalp Injections Are Needed to See Results?

At present, there is no standard treatment frequency that applies to all scalp injections.

Clinical studies have also used different approaches depending on the injected ingredient, such as observing progress for several months after a single session or treating repeatedly over multiple sessions.

Therefore, rather than simply counting the number of injections, it is more important to check whether hair thickness and density are actually changing.

In my hair loss consultations, I consider it important to review both the changes patients feel and scalp photography, which shows how much existing hair is being maintained and how thinning hair is changing.

Based on this objective assessment, we can determine whether additional treatment is needed.

5. Frequently Asked Questions

Q. Will a single scalp injection be effective?

Some studies have observed improvements in hair-related indicators even after a single session. However, individual responses vary, and long-term effects cannot be guaranteed.

Q. Can injection treatments alone replace hair loss medications?

In male and female pattern hair loss, medications such as finasteride, dutasteride, and minoxidil play an important role. Depending on the patient’s condition, scalp injections may be considered as a supplementary treatment.

Q. Do I have to keep getting scalp injections?

Not necessarily. If the response to treatment is insufficient or side effects occur, the treatment plan should be re-evaluated. Conversely, if the effects are confirmed, the need for maintenance treatment can be decided on an individual basis.

6. What Matters More Than Treatment Frequency Is Changes in Your Hair

Scalp injection for hair loss is one treatment method aimed at improving the environment around hair follicles and promoting hair growth.

For some ingredients, positive study results showing actual improvements in hair density and thickness have been reported.

However, treatment outcomes vary depending on the type and progression of hair loss, the ingredients used, and individual response.

What matters in scalp injection treatment is not simply undergoing many sessions, but allowing adequate time for observation, checking actual changes in hair, and deciding whether to continue treatment.

References

Effects and Safety of Botulinum Toxin Injection in Treatment of Androgenetic Alopecia: A Meta-analysis and Systematic Review. Dermatologic Surgery. 2025.

Polydeoxyribonucleotide in Female Pattern Hair Loss: Current Evidence and Knowledge Gaps. Journal of Cosmetic Dermatology. 2026.

Exosomes and Hair Regeneration: A Systematic Review of Clinical Evidence Across Alopecia Types and Exosome Sources. 2025.

American Academy of Dermatology. Hair loss: Diagnosis and treatment.

※ This article is intended to provide general medical information. Treatment methods and frequency may vary depending on individual hair loss type and condition.

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