Does hair dye get absorbed into the bloodstream?

Scientific studies have shown that some chemicals used in hair dyes can, in fact, be absorbed through the skin and enter the bloodstream in small quantities. This raises important questions about chemical exposure and the potential health implications of frequent or long-term hair coloring, leading many to ask, "Does hair dye get absorbed into the bloodstream?"

Quick Summary

Yes, some hair dye chemicals are absorbed into the bloodstream, primarily through the scalp, though the amount is typically small. Factors like the type of dye, skin integrity, and frequency of use influence the level of absorption and associated health concerns.

Key Points

• Absorption is Possible: Small amounts of certain hair dye chemicals, particularly in permanent dyes, can be absorbed through the scalp and hair follicles into the bloodstream.

• Risks are Minimal for Casual Users: Major health organizations indicate that personal hair dye use is not considered a significant cancer risk for most people, though long-term effects are still studied.

• Frequency Matters: The amount of chemical exposure and potential health concern is greater for those with long-term, repeated or occupational exposure, such as hairdressers.

• Scalp Condition is Crucial: A damaged, irritated, or sunburned scalp allows for higher absorption of chemicals. Always perform a patch test and do not apply dye to an unhealthy scalp.

• Safer Alternatives Exist: Semi-permanent dyes, natural dyes like henna, and foils for highlights minimize scalp contact and reduce the potential for chemical absorption.

• Protective Measures are Recommended: Wearing gloves, working in a well-ventilated area, and not leaving dye on longer than necessary can all help minimize exposure.

The science of hair dye absorption

The process of hair dyeing involves a chemical reaction that alters the hair's natural pigment. Permanent dyes, in particular, use a potent mix of chemicals to penetrate the hair shaft and bond with its keratin proteins. The active ingredients, such as p-phenylenediamine (PPD) and ammonia, are designed to penetrate, and they can also be absorbed by the highly vascularized scalp. While the amount of absorption is generally considered small for a single use, the cumulative effect of repeated exposure is what concerns researchers.

How chemicals enter the bloodstream

There are two primary pathways for hair dye chemicals to enter the body's circulation:

• Dermal Absorption: The most direct route is through the skin of the scalp. The scalp contains numerous hair follicles and is rich with blood vessels. Chemicals can be absorbed through the epidermal layer and, if skin is irritated or damaged, this absorption can increase. Tiny dye molecules are more likely to pass through this barrier.
• Inhalation: During the application process, volatile organic compounds (VOCs) and chemical fumes from the hair dye can be inhaled. This allows chemicals to enter the lungs and be absorbed into the bloodstream through the respiratory system.

Understanding the chemical composition

Hair dyes, especially permanent ones, contain a cocktail of ingredients. Here is a breakdown of some key chemicals and their potential for absorption:

• Para-phenylenediamine (PPD): A common colorant, PPD is a known allergen and a small molecule, making it more likely to be absorbed through the skin. Darker dyes typically contain higher concentrations.
• Ammonia: An irritant used to open the hair cuticle, ammonia can irritate the skin and respiratory tract, potentially increasing the permeability of the scalp to other chemicals.
• Hydrogen Peroxide: The developer in permanent dyes, this substance oxidizes the hair's melanin and the colorant molecules. It can also cause skin irritation.
• Resorcinol: A color-developing agent, resorcinol is also an irritant and potential endocrine disruptor.

Factors influencing absorption

The rate and amount of chemical absorption are not uniform for everyone and are influenced by several factors:

• Type of Dye: Permanent dyes, due to their chemical composition designed for deep penetration, have a higher potential for absorption than semi-permanent or temporary dyes, which only coat the hair shaft.
• Frequency of Use: People who dye their hair frequently or have long-term occupational exposure (like hairdressers) have a higher cumulative dose of chemicals entering their system.
• Scalp Health: An irritated, broken, or sun-damaged scalp provides less of a barrier, allowing for easier and greater absorption of chemicals.
• Genetic Factors: Some research suggests genetic variations in liver enzymes (like slow NAT2 acetylation) can affect how the body metabolizes hair dye chemicals, potentially increasing risk for some individuals.

Comparing dye types

Feature	Permanent Dyes	Semi-Permanent Dyes	Henna/Natural Dyes
Absorption Risk	Higher; contains smaller molecules that penetrate the hair shaft and scalp.	Lower; molecules are larger and primarily coat the hair.	Lowest; generally uses plant-based materials with little to no scalp absorption.
Longevity	Permanent, until hair grows out or is re-dyed.	Fades over several shampoos, lasting a few weeks.	Varies; can be long-lasting but fades over time.
Primary Chemicals	PPD, ammonia, hydrogen peroxide, resorcinol, and others.	Varying chemicals, often lacking ammonia and PPD.	Plant-derived compounds (e.g., lawsone in henna).
Allergy Risk	Higher, especially from PPD.	Lower, but patch testing is still recommended.	Possible, as any plant-based product can cause allergies.
Hair Damage	Can be significant due to strong chemicals altering hair structure.	Generally less damaging than permanent dyes.	Minimal, often conditioning the hair.

Health concerns and the bigger picture

While the American Cancer Society notes that studies have not found a consistent link between personal hair dye use and cancer risk for most people, the topic remains under investigation. The International Agency for Research on Cancer (IARC) classifies occupational exposure for hairdressers as "probably carcinogenic to humans," primarily due to the repeated, long-term exposure. This highlights that the amount and duration of exposure are critical factors in potential health risks. Recent studies continue to provide mixed results regarding personal use and health risks like breast and bladder cancer, with some suggesting a slightly elevated risk for certain groups, like frequent, long-term users of dark permanent dyes.

Minimizing absorption and risk

For those concerned about chemical absorption, there are several steps to take:

1. Reduce Frequency: Extending the time between colorings can lower cumulative exposure.
2. Use Safer Alternatives: Consider semi-permanent or natural dyes, like henna, which are less likely to be absorbed. Always read labels carefully, as some "natural" dyes may still contain chemicals.
3. Choose Lighter Shades: Lighter-colored permanent dyes generally contain fewer harsh chemicals like PPD.
4. Protect Your Scalp: Avoid coloring if your scalp is irritated or damaged. Use gloves during application and follow all product instructions carefully.
5. Seek Professional Guidance: An experienced hairstylist can minimize scalp contact. For those with health concerns, consulting a doctor is always a good idea, especially during pregnancy.

Ultimately, while a small degree of absorption does occur, the health implications for the average person are still being researched. Understanding the chemicals involved and taking precautions is key to making an informed decision about hair coloring. For more information on hair dye safety, the Environmental Working Group offers detailed resources on cosmetic ingredients: EWG Skin Deep Database.

Conclusion

The question, "Does hair dye get absorbed into the bloodstream?", can be answered with a qualified yes—small amounts of some chemicals can enter the bloodstream through the scalp and inhalation. However, the vast majority of health organizations do not consider personal use a high-risk activity based on current evidence. The biggest takeaway is that informed choice and safety precautions are essential. By opting for safer product types, protecting the scalp, and being mindful of frequency, you can reduce potential exposure and enjoy coloring your hair with greater peace of mind.

Frequently Asked Questions

Which chemicals in hair dye can enter the bloodstream?

Primary colorants like p-phenylenediamine (PPD), along with ammonia and resorcinol, are among the chemicals found in hair dyes that can be absorbed through the scalp and enter the bloodstream, especially with frequent use of permanent dyes.

Does the type of hair dye affect absorption into the bloodstream?

Yes, permanent hair dyes, which use smaller molecules to penetrate the hair shaft, pose a greater risk of scalp absorption than semi-permanent or temporary dyes. Natural and vegetable-based dyes generally have the lowest absorption risk.

Is hair dye absorption dangerous?

For occasional, personal use, the amount of chemical absorption is generally very small and not considered dangerous by most health organizations. However, long-term occupational exposure has been linked to increased risk of certain cancers, which highlights the importance of cumulative exposure over time.

Does having a healthy scalp reduce hair dye absorption?

Yes, a healthy, intact scalp provides a more effective barrier against chemical absorption. An irritated, broken, or sunburned scalp can increase the rate at which chemicals are absorbed into the bloodstream.

Can inhaling hair dye fumes lead to chemical absorption?

Yes, in addition to scalp absorption, inhaling the volatile chemicals from hair dye fumes can allow them to be absorbed into the bloodstream through the lungs. Proper ventilation is an important safety measure.

Are black hair dyes more dangerous regarding bloodstream absorption?

Darker permanent hair dyes, including black, often contain higher concentrations of chemicals like PPD to achieve the desired color. This can lead to a higher potential for absorption and allergic reaction compared to lighter shades.

Should pregnant women be concerned about hair dye entering the bloodstream?

Because absorption is minimal, many doctors advise that hair dyeing during pregnancy is likely safe. Still, many choose to wait until after the first trimester or use safer alternatives like highlights (which minimize scalp contact) or natural dyes as a precaution. Consulting with a physician is recommended.

How can I minimize hair dye absorption?

You can minimize absorption by wearing gloves, using semi-permanent or natural dyes, choosing lighter colors, working in a well-ventilated space, and ensuring your scalp is healthy and free of irritation before coloring.