Ingredient review
Dihydroxyindoline HBr
INCI: DIHYDROXYINDOLINE HBR
A synthetic hair dye intermediate that helps create rich, lasting color but may cause skin irritation in sensitive individuals.
In plain English
Dihydroxyindoline HBr is a lab-made chemical used in permanent hair dyes. It works by reacting with other ingredients inside the hair shaft to form large color molecules that stay put, giving you long-lasting hair color. Because it's a reactive chemical, it can sometimes irritate the scalp or skin, especially if you have sensitive skin or allergies to hair dye.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Main practical flags: irritation is moderate; clogging risk is low.
- Source
- synthetic
- Evidence
- moderate
- Irritation
- moderate
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Dihydroxyindoline HBr can be useful, but watch for some irritation potential.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Dihydroxyindoline HBr.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
moderateCan bother some users, especially with frequent use, damaged skin, or strong companion ingredients.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
A synthetic indole derivative, specifically the hydrobromide salt of 5,6-dihydroxyindoline. It is used as a precursor in oxidative hair dye systems, where it helps generate color molecules inside the hair.
How it works
In a hair dye product, Dihydroxyindoline HBr is mixed with an oxidizing agent (like hydrogen peroxide) just before application. The oxidation triggers a chemical reaction that converts the small, colorless molecule into larger, colored pigments that become trapped inside the hair cortex, resulting in permanent color that resists washing.
Pros
Long-lasting color
The color molecules formed inside the hair shaft resist washing, so your hair color stays vibrant for weeks.
Versatile shade range
When combined with other dye precursors, it helps create a wide variety of natural and fashion shades.
Cons and cautions
Potential skin irritation
As a reactive chemical, it can cause redness, itching, or burning on the scalp or skin, especially for those with sensitivities.
Requires patch testing
You must do a patch test 48 hours before each use to check for allergic reactions, which adds time and effort.
Best for
- People looking for permanent, long-lasting hair color
- Those who have successfully used oxidative hair dyes without irritation
Use caution if
- Individuals with known sensitivity or allergy to hair dye chemicals
- People with damaged or very sensitive scalps
Usage tips
Safety summary
Dihydroxyindoline HBr is considered safe for use in hair dyes when formulated correctly and used as directed. However, it can cause skin irritation and allergic reactions in some individuals. Patch testing is essential, and those with known dye allergies should avoid it.
Research notes
Studies confirm that Dihydroxyindoline HBr is an effective oxidative dye precursor. Its safety profile is similar to other common hair dye intermediates, with irritation and sensitization risks that are manageable through proper formulation and user precautions.
Common label clues
- Typical concentration
- 0.1% to 2% in hair dye formulations
- Regulatory status
- Approved for use in cosmetic hair dyes in the EU and US when used within concentration limits and with proper labeling. Always check local regulations.
- Common uses
- Permanent hair dyes, Hair colorants
- Environmental note
- As a synthetic chemical, it may contribute to wastewater pollution. Proper disposal of unused dye mixtures is recommended.
Good to know
- Dihydroxyindoline HBr is often used in combination with other dye intermediates like resorcinol or m-aminophenol to achieve specific shades.
- It is not typically found in rinse-off products like shampoos or conditioners.
Common questions
What is Dihydroxyindoline HBr in beauty products?
Dihydroxyindoline HBr is a lab-made chemical used in permanent hair dyes. It works by reacting with other ingredients inside the hair shaft to form large color molecules that stay put, giving you long-lasting hair color. Because it's a reactive chemical, it can sometimes irritate the scalp or skin, especially if you have sensitive skin or allergies to hair dye.
What does Dihydroxyindoline HBr do in a beauty product?
In a hair dye product, Dihydroxyindoline HBr is mixed with an oxidizing agent (like hydrogen peroxide) just before application. The oxidation triggers a chemical reaction that converts the small, colorless molecule into larger, colored pigments that become trapped inside the hair cortex, resulting in permanent color that resists washing.
Is Dihydroxyindoline HBr safe for most people?
Dihydroxyindoline HBr is considered safe for use in hair dyes when formulated correctly and used as directed. However, it can cause skin irritation and allergic reactions in some individuals. Patch testing is essential, and those with known dye allergies should avoid it.
Who should be careful with Dihydroxyindoline HBr?
Individuals with known sensitivity or allergy to hair dye chemicals People with damaged or very sensitive scalps
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.