Which metal is safest for hair/scalp? Bismuth, silver or zinc oxide?

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Discussion Overview

The discussion revolves around the safety and effectiveness of using bismuth, silver, or zinc oxide in hair treatments, particularly in combination with henna. Participants explore the potential effects of these metals on hair appearance and scalp absorption, considering both historical practices and modern safety concerns.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants express interest in which of the three metals—bismuth, silver, or zinc oxide—might provide the most shine to hair when used with henna.
  • One participant notes that zinc oxide appears to be the most innocuous based on Material Safety Data Sheets (MSDS) for each metal.
  • Concerns are raised about the safety of bismuth, particularly regarding its potential health effects when inhaled or ingested.
  • Another participant mentions that silver oxide is unsuitable for cosmetic use due to its dark color, which would not contribute to shine.
  • There are warnings about the handling of metal powders, including the flammability of certain materials and the need for adult supervision when dealing with them.
  • Some participants share conflicting views on the safety of bismuth, with references to its common use in products like Pepto Bismol contrasted with potential harmful effects.

Areas of Agreement / Disagreement

Participants do not reach a consensus on which metal is the safest or most effective for hair treatment. Multiple competing views remain regarding the safety and suitability of bismuth, silver, and zinc oxide.

Contextual Notes

Participants reference MSDS documents to support their claims, but there are limitations in the completeness of the toxicological information available for each metal. Additionally, the discussion includes varying levels of expertise among participants, which may affect the interpretation of safety and handling guidelines.

Torey
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TL;DR
Which metal would be safest to apply to the hair if the scalp were to absorb any of the metal? Would it be Bismuth, silver or zinc oxide? Thanks!
A little background on my experiment … "Henna" (Lawsonia plant hair dye going way back to ancient times) used to be combined with metallic salts to cause it to adhere to the hair and make it thicker with cumulative use. In foreign countries "compound henna" is still being sold but often w/ harmful metals like lead as well as less harmful metals like zinc oxide. But, I want to combine it with the safest metal. Also, I understand that some metals make the hair dull (like iron) while others make hair shiny. Anyone have any clue which of the three metals - bismuth, silver or zinc oxide might yield the most shine to a strand of hair? Thanks for any input.
 
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Torey said:
Summary: Which metal would be safest to apply to the hair if the scalp were to absorb any of the metal? Would it be Bismuth, silver or zinc oxide? Thanks!

A little background on my experiment … "Henna" (Lawsonia plant hair dye going way back to ancient times) used to be combined with metallic salts to cause it to adhere to the hair and make it thicker with cumulative use. In foreign countries "compound henna" is still being sold but often w/ harmful metals like lead as well as less harmful metals like zinc oxide. But, I want to combine it with the safest metal. Also, I understand that some metals make the hair dull (like iron) while others make hair shiny. Anyone have any clue which of the three metals - bismuth, silver or zinc oxide might yield the most shine to a strand of hair? Thanks for any input.
To be clear, you are comparing two metals (Bismuth and Silver) and one metal oxide (Zinc Oxide).
In case you were not, Bismuth Oxide and Silver Oxide and both unsuitable for cosmetics.

A quick check of the MSDS for each of these materials indicates that Zinc Oxide is the most innocuous.

From https://www.espimetals.com/index.php/msds/51-Bismuth
11 TOXICOLOGICAL INFORMATION

Likely Routes of Exposure: Inhalation, skin, eyes.

Symptoms of Exposure: May cause irritation.

Acute and Chronic Effects: Prolonged inhalation of bismuth dusts may cause mental changes, nervousness, blood changes, lymphocytosis and bone marrow depression. Ingestion of bismuth compounds may cause nausea, vomiting, diarrhea, and pigmentation of the skin and mucous membranes.

Acute Toxicity: No data

Carcinogenicity: NTP: Not identified as carcinogenic IARC: Not identified as carcinogenic

To the best of our knowledge the chemical, physical and toxicological characteristics of the substance are not fully known.
From https://www.espimetals.com/index.php/msds/274-Silver:
11 TOXICOLOGICAL INFORMATION

Likely Routes of Exposure: Inhalation, skin, eyes.

Symptoms of Exposure: May cause irritation.

Acute and Chronic Effects: Silver metal is relatively inert. Chronic exposure to soluble silver compounds may cause a permanent bluish-gray discoloration of the skin and eyes known as argyria.

Acute Toxicity: No data

Carcinogenicity: NTP: Not identified as carcinogenic IARC: Not identified as carcinogenic

To the best of our knowledge the chemical, physical and toxicological characteristics of the substance are not fully known.
From https://www.espimetals.com/index.php/msds/309-Zinc Oxide:
V. HEALTH HAZARD INFORMATION

Effects of Exposure:

Zinc compounds have variable toxicity, but generally are of low toxicity. Zinc is not inherently a toxic element. However, when heated it evolves a fume of zinc oxide which, when inhaled fresh, can cause a disease known as “brass founders” “ague,” or “brass chills”. Zinc oxide dust which is not freshly formed is virtually innocuous. There is no cumulative effect form the inhalation of zinc fumes (Sax, Dangerous Properties of Industrial Materials, eighth edition).

Acute Effects:

Inhalation: May cause respiratory tract irritation with nasopharyngitis and laryngitis.

Ingestion: Moderately toxic by ingestion.

Skin: May cause irritation.

Eye: May cause irritation

Chronic Effects:

Inhalation: May cause human systemic effects.

Ingestion: No chronic health effects recorded.

Skin: No chronic health effects recorded.

Eye: No chronic health effects recorded.

Target Organs: No target organs recorded.

Medical Conditions Generally Aggravated by Exposure: Pre-existing respiratory disorders.

Carcinogenicity: NTP: No IARC: No OSHA: No
 
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I get you, Borek. The way I found Physics Forums in the first place was I stumbled on a thread where another person was asking about the safety of bismuth. He had a number of answers, with almost everyone thinking it was safe, but I wondered how this compared to other metals. But, I realize that "Physics Forum" is not making any recommendations - I'm just finding out the opinions of different members. Thanks.
 
.Scott said:
To be clear, you are comparing two metals (Bismuth and Silver) and one metal oxide (Zinc Oxide).
In case you were not, Bismuth Oxide and Silver Oxide and both unsuitable for cosmetics.

A quick check of the MSDS for each of these materials indicates that Zinc Oxide is the most innocuous.

From httying ps://www.espimetals.com/index.php/msds/51-Bismuth

From https://www.espimetals.com/index.php/msds/274-Silver:

From https://www.espimetals.com/index.php/msds/309-Zinc Oxide:
Thanks for all the pasted info. As you can see, I am a total novice at this … I ordered some 99.9% powdered bismuth but wanted to learn a little more first. I've heard most people say (and toxicology reports) that it's relatively safe - especially considering Pepto Bismol - but I've also read a few things that make it sound harmful. So, it's been confusing. But, I'm now also interested in checking out zinc oxide. Thanks.
 
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There are additional problem in handling Bismuth in powdered form.
Read the MSDS thoroughly - especially with regard to inhaling the powder.

This material should only be handled under adult supervision. If you are not an adult, get one.
 
.Scott said:
If you are not an adult, get one.
Amazon is having a special this week... 😉
 
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You also have to consider that Silver Oxide is a dark brown almost black powder. So that rules out it use to provide "shine".

BoB

Edit: Be careful with metal powders as they tend to be flammable. Some of them spontaneously.
 
Do not fool with materials if you have insufficient training, insufficient education, or insufficient equipment to handle or use them.
 
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  • #10
For detailed health information, I've found the US National Institutes of Health (NIH) to be very useful. Try a Google search of the material followed by "site:nih.gov" (without the quotes).

For example the Search field would be: zinc oxide site:nih.gov

https://www.google.com/search?&q=zinc+oxide+site:nih.gov
Cheers,
Tom