HairScience Comparative Score Criteria

The International Hair Science Association’s Comparative Scoring Criteria is based on an accurate, unbiased analysis of peer-reviewed published data. These scores have been calculated after the analysis of data from over 300 papers published in peer-reviewed journals. We aim to be as transparent as possible with our process and have detailed our methodology for the creation of these scores below. 

Calculating these scores was performed by analyzing five factors, normalizing the values from the resulting data by categorizing results, then applying weighting factors to each category, and blending those values into a singular number between 0 and 100. The resulting scores allow our readers to easily compare different treatments side by side.

The Comparative Scoring Criteria was created to remove bias when assessing different treatments options. The factors considered when creating this criteria, such as effectiveness and side effects, are relevant to all users of hair loss treatments.

Factors Considered For Each Treatment 

The International Hair Science Association’s Comparative Scoring Criteria accounts for five factors blended into a final score that helps you compare different treatments side by side. The five factors we have considered include the following:

  • Effectiveness of the hair regrowth treatment
  • Quality of data
  • Safety and side effects
  • Convenience of use
  • Inclusivity in regards to sex, gender, and skin color

The assessment of each factor, particularly in regards to the effectiveness of the hair regrowth treatment and quality of data, focuses on androgenetic alopecia, the most common form of hair loss. Most people experience symptoms of androgenetic alopecia at some point in their lives. 

At this time, the Food and Drug Administration (FDA) has only approved hair loss treatments for androgenic alopecia. As such, the compilation of information used to create the Comparative Scoring Criteria is primarily related to the routes of administration and doses recommended for this type of hair loss. Doses and routes of administration approved by the Korean Ministry of Food and Drug Safety and Pharmaceuticals and Medical Devices Agency of Japan​​ have also been considered.

Some of the treatments considered are also used for other forms of hair loss. However, they are not always approved for that indication and are usually prescribed by doctors off-label. These different types of hair loss are discussed in HairScience.org’s website content. However, studies focused on these alternative types of hair loss were not used to develop the Comparative Scoring Criteria, except when insufficient studies related to androgenetic alopecia were available for a particular treatment.  

Treatment Classification Ratings

Each treatment has been rated for each criterion by our medical team based on clinical research data, FDA-approved labeling and instructions of use, and other relevant information from trusted sources such as the Korean Ministry of Food and Drug Safety and Pharmaceuticals and Medical Devices Agency of Japan​​.

Microneedling
PrP
LLLT
Minoxidil
Finasteride
Dutasteride
Supplements
Shampoo
Hair Transplants
CLASSIFICATION
Effectiveness
C
B
C
C
C
C
C
D
A
Data Quality
B
A-
A-
A-
B
B
D
B-
C-
Convenience
A
C
A
A
B
B
A
A
C
Safety
B
A
A
B
C
C
A
A
D
Inclusivity
A
A
B
A
C
C
A
A
A

Legend

Effectiveness: A: >40 hair/cm² (excellent regrowth); B: 20-39.99 hair/cm² (great regrowth); C: 10-19.99 hair/cm² (moderate regrowth); D: 5-9.99 hair/cm² (minor regrowth); E: <5 hair/cm² (ineffective).

Data Quality: A: between 4.01 and 5 points; A-: between 3.01 and 4 points; B: between 2.01 and 3 points; B-: between 1.01 and 2 points; C: between 0.01 and 1 points; C-: between 0 and -0.99 points; D: between -1 and -1.99 points; D-: between -2 and -2.99 points; E: between -3 and -3.99 points; E-: between -4 and -5 points. For details on how points were determined, please refer to the Data Quality section below. 

Convenience: A: Over-the-counter home use; B: Prescription-only home use; C: Only feasible by visiting a medical clinic.

Safety: A: Either mild or no side effects; B: moderate side effects can occur; C: severe side effects can occur; D: irreversible or debilitating side effects can occur.

Inclusivity: A: For both biological sexes, regardless of gender identity; B: For both biological sexes, regardless of gender identity, but limited to those with Fitzpatrick skin type I–IV; C: Exclusively for either biological sex, D: Exclusively for either biological sex and limited to those with Fitzpatrick skin type I–IV.

Effectiveness

Increased hair density is considered one of the best parameters to measure hair regrowth in clinical trials. The Comparative Scoring Criteria uses the effectiveness parameter, defined as the increase in hair density following treatment, to categorize the different treatments. Our assessment specifically sought a quantitative measurement. We defined this as the difference between placebo and treatment groups when determining the increase in hair density (measured in hairs/cm²) between the beginning and end of the treatment period. In cases where there was no placebo group available, the result was based only on the difference in hair density from the beginning of treatment to the end of the treatment. 

An extensive literature was performed to identify and review clinical trials with relevant results. A final weighted average of the increase in hair density for each treatment has been computed, using the number of subjects in each clinical trial as a weighting factor.

In our search, we prioritized the inclusion of clinical trials that met the following criteria:

  1. Patients with androgenetic alopecia had been recruited.
  2. The full text of the study was available.
  3. Studies included a placebo group.
  4. The study provided data that included the quantitative hair density before and after treatment for each group studied.
  5. At least one group in the study was given monotherapy treatment. Results combining the analyzed treatment with other treatments were not incorporated into the Comparative Scoring Criteria. 

However, the above criteria had some limitations for some of the treatments. The following exceptions were made:

No clinical trial evaluating hair supplement effectiveness in people with androgenetic alopecia and reporting comparable hair density data was found. The only suitable trials found focused on the recruitment of patients with self-reported hair thinning. A penalization in the Data Quality criterion has been introduced to address this issue.

Hair transplant treatment clinical trials do not assess hair density but hair graft survival. This refers to the number of grafts that remain viable in the transplanted area after the treatment. In this case, effectiveness has been assessed by taking three factors into account:

  1. Hair graft survival
  2. The average hairs per graft transplanted
  3. The average number of grafts per transplant (effectiveness in hairs/cm² = hair graft survival × average hairs per graft × average grafts per transplant).

Clinical trials evaluating microneedling effectiveness did not include a sham-controlled group (equivalent to placebo) as it is not feasible to blind participants to this treatment.

Due to the limited number of clinical trials evaluating hair growth shampoos, some of the ones considered are not placebo-controlled. The data quality factor will assess this factor to penalize the overall score. 

Other relevant considerations that should be considered when looking at our classification are that supplements and shampoos are not standardized treatments for androgenic alopecia but are often used as adjuvant treatments. They have also been established as helpful solutions for specific types of hair loss. Our results are exclusively based on products that have published clinical data. The overall effectiveness of every product in the market is undoubtedly smaller than what our classification shows, with some of the products being completely ineffective for androgenetic alopecia.

Additionally, in cases where there are different routes of administration for a treatment, we have selected the dose and route of administration recommended by the USA’s Food and Drug Administration, Korean Ministry of Food and Drug Safety and Pharmaceuticals, and Medical Devices Agency of Japan. The Comparative Scoring Criteria consequently considered the following:

    • Minoxidil: Topical foam or liquid solution in concentrations of 2 and 5 percent.
    • Finasteride: Oral pill to be taken as a 1-milligram daily dose.
    • Dutasteride: Oral pill taken in daily doses of 0.1 or 0.5 milligrams.

Data Quality

This factor assesses the quality of data compiled to obtain results for the Effectiveness criterion while capturing sources of bias. A rating has been assigned to each clinical trial that was considered in the effectiveness factor. The rating of each clinical trial can be computed based on the positive or negative answers to the questions below. A global weighted score for each treatment has been calculated, taking into account as a weighting factor the size of the clinical trial (i.e., the number of clinical trial patients evaluated) and each of the individual clinical trial ratings considered.

QUESTIONS FOR THE SCALE
Is randomization mentioned?
Is the randomization appropriate?
Is a blinding method mentioned?
Is the blinding method appropriate?
Are all patients accounted for, or is proper reasoning for excluded patients given?
Have all participants been diagnosed with androgenetic alopecia?
Did the study include both men and women?
YES
1
1
1
1
1
0
0
NO
0
0
0
0
0
-4
-1

Safety

Our team has gathered possible adverse events for each treatment. Each adverse event has been categorized by cross severity indexing to compare different side effects or adverse events side-by-side. Please note that this index does not assess the severity of how a particular side effect may present in patients. 

Based on the number of side effects and each cross severity index for each treatment, the Safety criterion has been categorized as follows:

A
B
C
D
Either mild or no side effects, including but not limited to local transitory side effects or local side effects that resolve by themselves after stopping the treatment.
Moderate side effects can occur, including but not limited to more concerning allergic reactions or infections that require systemic treatment.
Severe side effects can occur, such as elevated liver enzymes which can lead to liver inflammation.
Irreversible or debilitating (affecting quality of life) side effects can occur.

Convenience

The Convenience criterion considers where the treatment needs to be administered and if its use requires the assistance of a trained professional. Home-based treatments are considered more convenient than those which require a visit to the clinic. If a treatment requires a prescription, a visit to a doctor is mandatory before the treatment can be obtained. Clinic-based treatments are performed on-site by trained professionals. Based on these factors, the Convenience criterion has been categorized as follows:

A
B
C
The treatment can be done at home and does not require a medical prescription
The treatment can be done at home but requires a medical prescription
The treatment can only be done in a clinical setting

Inclusivity

It is common for certain treatments to be limited to individuals due to pre-existing health conditions. However, we considered a broader lack of inclusivity — specifically limitations due to biological sex, gender (particularly in cases where the individual is taking hormone replacement therapy), and skin tone (specifically, skin phototype), to be of note.

Skin tone was considered based on the Fitzpatrick classification system, which is made up of six phototypes. These phototypes have been established based on a person’s tendency to sunburn and ability to tan, which is related to their risk of skin damage from UV exposure and aesthetic procedures. An approximation of the Fitzpatrick classification system is shown below.

Fitzpatrick Skin Phototypes

A visual representation of the six Fitzpatrick skin phototype

Adapted from: Gupta, V., & Sharma, V. K. (2019). Skin typing: Fitzpatrick grading and others. Clinics in dermatology, 37(5), 430-436.

Phototherapy (i.e., laser hair therapy and other aesthetic treatments using light) is not always safe or effective in people with darker skin tones, largely due to the melanin content in skin. As a consequence, phototherapy is often restricted for two skin tones: Fitzpatrick skin type V and VI. The melanin in these skin tones may increase absorption, which has the potential to increase the risk of side effects.

Based on these limitations, treatments are classified as:

A
B
C
D
For both biological sexes (male and female), regardless of gender identity
For both biological sexes (male and female), regardless of gender identity, but limited to those with Fitzpatrick skin type I–IV
Exclusively for either biological sex (male or female)
Exclusively for either biological sex (male or female) and limited to those with Fitzpatrick skin type I–IV

HairScience Score Calculation

Each treatment has been rated for each criterion by our medical team based on clinical research data, FDA-approved labeling and instructions of use, and other relevant information from trusted sources such as the Korean Ministry of Food and Drug Safety and Pharmaceuticals and Medical Devices Agency of Japan​​.

HS Score = Effectiveness x Data Quality x Convenience x Safety x Inclusivity x Normalization Factor

Factor Weights

The maximum weight for each factor is 100%, equivalent to the rating A. Penalties have been applied to account for less effectiveness, lower quality of data, a riskier profile, less convenience, and less inclusivity. In the case of Effectiveness, each lower category is reduced in increments of 25%. The discount for each lower category is 10% for the four other factors. 

Examples:

  • A treatment rated A- in the Data Quality factor is discounted 10%, and a treatment rated B is discounted 20%. 
  • A treatment rated B in the Convenience factor is discounted 10%, and a treatment rated C is discounted 20%.
  • A treatment rated D in the Safety factor is discounted 30%.
  • A treatment rated B in the Effectiveness factor is discounted 25%, ending up with an Effectiveness weight of 75% 
  • A treatment rated C in the Effectiveness factor is discounted 50%, ending up with an Effectiveness weight of 50%

Sources 

Effectiveness and safety data have been sourced from scientific peer-reviewed literature. References used for each treatment can be found on the respective page for that treatment.

Hair science research is a continually evolving endeavor, and our work aims to include the most up-to-date research. If you find any additional sources that we haven’t considered, please send us the information at contact@hairscience.org.