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Seeing my 1-year-old nephew play in a tub, with shampoo all over his hair and face, is one of the simple joys of life, as it is of course for millions of parents around the country. But being a physician I wanted to make sure that everything that touched his skin and eyes was chemically safe. And I knew that labels like “tear-free” used for shampoos were not regulated by the federal government. So I decided to take a look.
There were so many things in the shampoo—a surfactant to keep it from separating into layers, a preservative, either natural or synthetic, and fragrance. All of them added up to get that bubbly foam, thick and creamy liquid, an easy rinse and low toxicity. But what was it that made these shampoos tear-free?
One common thing manufacturers do is to dilute the shampoo with water to prevent eye irritation. Another way is to adjust the pH of the product to near 7, which is the non-stress area, lower than shampoos made of soap. But there is a far more sinister technique as well.
Some shampoos add anesthetizing agents, which essentially numb the baby’s eyes so that the sting is not felt. These ingredients are usually labeled as PEG, followed by a number, like PEG-50 or PEG-100. So when there is an irritant in the formulation, the eyes, being temporarily numbed, do not react to any negative effects of these ingredients.
The structure and function of an infant’s eyes continue to develop over the first year of life. Babies blink less often, and tearing of their eyes is less robust. In addition, babies tend to rub their eyes more, and they continue to fine-tune their defensive eye closure in the first 5–7 months of life. Because of these reasons, substances can be more easily rubbed into their eyes, and there is a greater potential for eyes to be exposed to shampoo or products used during bath-time.
A baby product should not contain irritants like sodium lauryl sulfate, an inexpensive foaming agent present in many formulations, which causes skin or eye irritation. Because of the greater risk, baby personal care products such as shampoo or bath products should ideally be evaluated for their eye irritation potential, to ensure that they are ultra-mild and safe and appropriate for use on babies.
A research in Stockholm in 2012 tested 19 baby bath and shampoo formulations on pain inducing receptors in the lab. The aim was to predict eye stinging before ever using them on animals or humans. The results of the study suggested that such models could be used widely to predict stinging in the eyes using the TRPV-1 pain channel.
For now, the use of gentle surfactants, which are less irritating than those used in other regular or adult shampoo, and staying away from chemicals like sodium lauryl sulfate and the numbing agents, can be the nearest cure to keep those beautiful eyes safe and tear-free.
This is a guest post for Essilor of USA, written by Harmandeep Singh, a contributor to NY City Lens and Global Post. He went to medical school in his hometown of Amritsar, Punjab in India and did his rotations at the medical schools of Harvard, Yale and Cornell Universities. Keep up with him by following him on Twitter, @drharmanboparai.z