Month: March 2014

Properties of Hair- Part 2

Though it may not be that obvious, water is an important component of hair. Its presence helps with the elasticity or pliability of hair. The water content of hair is between 15-35%. The high variability is due to the hairtype and health of the hair fibre. Hair that is damaged is less likely to hold onto water. ‘

Water has the potential to increase not only the weight of the hair fibre but also the diameter. This is referred to as the swelling potential of hair. It can increase to nearly 14% in diameter, but less than 2% in length. Other reagents such as sodium lauryl sulfate, formic acid, and thioglycolic acid have a greater effect on the swelling potential of hair, hence the reason for these products to potentially damage hair.

The more the hair absorbs is the more damaged the hair, indicating that the hair shaft is more porous. This is what is  termed as “porosity”.  Hair that absorbs more water has decreased tensile strength i.e. it easily breaks. The porosity of the hair shaft is about 20%, allowing a weight increase of 12–18% when soaked in water. The absorption rate is very rapid, with 75% of the maximum absorbable water entering the hair shaft within 4 minutes.

However, as quickly as the hair absorbs water, it can quickly lose it. Those with quite porous hair can attest to this. Water has been shown to stay in the hair shaft better if attached to some highly osmotic molecule like sorbitol, or some other hygroscopic (water-loving) substance such as glycerin. These molecules allow water from the atmosphere to stay longer in contact with the hair shaft. This increases the moisture content of the hair shaft and thus allows the hair to not only feel better but to look better as well.

References

Syed AN, Ayoub H. Correlating Porosity and Tensile Strength of Chemically Modified Hair. Cosmet Toil 2002; 117: 57-64.

Draelos MD, Zoe Diana (2007-04-17). Hair Care (Kindle Locations 331-334). Informa Healthcare. Kindle Edition.

Egawa, M., Hagihara, M. and Yanai, M. (2013), Near-infrared imaging of water in human hair. Skin Research and Technology, 19: 35–41

Question of the Month -March

questiontext

 

Hi Doc,

I have food allergies to wheat. I’m diligent with buying gluten free foods. Lately I’ve been noticing that my scalp  has been burning/itching when I use products with wheat in them? Should I be avoiding these as well? Am I being ridiculous?

 

answertext

 

Hi Gluten-Free,

Your world may be becoming a bit more complicated. There has been some evidence that persons with food allergies such as wheat, egg, or oat, are also allergic to the proteins in topical form i.e. skin product, hair product. These persons however had Atopic Eczema which is commonly seen with persons who have food allergies.  You did not mention that you had Atopic eczema, but the possibility for you to become allergic topically to wheat proteins, is not improbable.

Even without these food allergies, there is a chance for regular persons, who do not have food allergies, to develop what we call  a Contact Dermatitis (Eczema) to these proteins.  Sadly, these hydrolysed wheat proteins are everywhere. They are popular as they have been found to help soothe irritated skin and helping to restore elasticity to the hair shaft.

So what will that mean for you?

You may have to try avoiding all hair and skin products with wheat proteins and see if that makes a difference. Ideally you should have what is called an allergy testing  by an allergist or a dermatologist who has special interest in allergy testing.

 

References

Varjonen, E., Petman, L. and Mäkinen-Kiljunen, S. (2000), Immediate contact allergy from hydrolyzed wheat in a cosmetic cream. Allergy, 55: 294–296.

Varjonen, E., Vainio, E. and Kalimo, K. (2000), Antigliadin IgE – indicator of wheat allergy in atopic dermatitis. Allergy, 55: 386–391.

Mailhol, C., Lauwers-Cances, V., Rancé, F., Paul, C. and Giordano-Labadie, F. (2009), Prevalence and risk factors for allergic contact dermatitis to topical treatment in atopic dermatitis: a study in 641 children. Allergy, 64: 801–806