This is an ancient topic, but let's dive into it briefly anyway.
Understanding Tear-Free Shampoo
Tear-free shampoo is a specially formulated product designed to be gentle on the eyes. The term “tear-free” implies that if the shampoo gets into the eyes, it won’t cause the stinging sensation that often leads to tears. But what exactly makes a shampoo tear-free? Let’s delve into the science behind it.
The Composition of Tear-Free Shampoo
The primary components of most shampoos are surfactants, which are compounds that help clean the hair by reducing the surface tension of water, making it easier to remove dirt and oil from the hair and scalp. However, in tear-free shampoos, the choice of surfactants is crucial because not all surfactants are created equal.
Tear-free shampoos typically use milder surfactants that are less likely to irritate the eyes. These are often long-chain synthetic surfactants such as amphoteric surfactants. They are gentler and contain fewer cleaning agents, reducing the likelihood of eye irritation. They don’t foam as well as sulfates and because they are gentler, they are not as good at cutting grease. This is not a problem for babies, but if your hair is really oily and dirty, you may have to shampoo twice (lather, rinse, repeat).
Sensitizing Ingredients
The secondary factor to look for is avoiding sensitizing materials such as fragrances. Fragrances and other additives may sting the eyes.
The Role of pH
Another factor that contributes to a shampoo being tear-free is its pH level. The pH level of a substance indicates how acidic or alkaline it is. Our skin and hair have a pH level between 4.5 and 5.5, and ideally, our hair care products should match this. However, too acidic and too alkaline will sting the eyes.
It is highly recommended to maintain the pH of shampoo between 5 and 7. If you are formulating for a tear-free shampoo, the ideal pH is 7.4 and 7.5, close to the pH of tears.[i] This is because any ophthalmic formulation outside the range 5.0–8.5 causes extra lachrymation.[ii]
So, tear-free shampoos should have a pH level in this range that is suitable for the eye area.
Dispelling Myths
There’s a common myth that tear-free shampoos contain numbing agents to prevent eye irritation. However, this is not true. The tear-free property of these shampoos comes from their mild formulation, not from any numbing agents.
In conclusion, tear-free shampoos are a safer, gentler option, especially for children or those with sensitive eyes. Their unique formulation ensures they clean the hair effectively without causing discomfort if they come into contact with the eyes.
Don't forget to look out for our next post and 3 easy Tear-Free Shampoo Formulas.
Happy learning!
References:
[i] Herbert W Heinrich, Ingeborg M Schmitt, Eyeliner Composition, US3639572A, 1972
[ii] Ludwig A, Reimann H. Eye. In: Bouwman-Boer Y, Fenton-May V, LeBrun PPH, editors. Practical pharmaceutics, an international guideline for the preparation, care and use of medicinal products. Switzerland: KNMP and Springer International; 2015. p. 163–88
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