Hair bleaching is a very common practice to add some oomph to hair, and it involves lightening the hair by varying levels. However, this process can be very aggressive on the hair thereby causing major internal damage to the hair fibers. Let’s find out why and what you should you keep in mind when bleaching your hair.
The process of hair bleaching
The bleaching kit usually consists of hydrogen peroxide (developer) as the principal oxidizing agent and salts of persulfate, often in the form of a powder to act as “accelerators” for the hydrogen peroxide reaction. Usually the pH of these systems is maintained between 9 and 11 with the help of a hair lightener base. The bleaching mixture paste/solution will lift the cuticles and penetrate into the cortex of the hair. There, the hair pigment (mainly melanin) is degraded. The extent of removal of the hair’s pigment dictates the end color of the hair. This is controlled through the volume strength (eg. 20V or 40V) of hydrogen peroxide and length of exposure time.
The chemical damage from hair bleaching
As mentioned above, the primary purpose of bleaching is to lighten the hair and this is most readily accomplished by oxidation. However, because of the severe reaction conditions required for destruction of hair pigments (melanin), side reactions with the hair proteins occur simultaneously. This occurs because hair is composed of protein (amino acids) and many of the groups on amino acids can also be oxidized. This results in the degradation of hair protein during bleaching. The oxidation of the amino acids such as cystine weakens the cuticles as well as the cortex of the hair fiber. Cuticles lifting (left) or removal (right) is very likely during bleaching as shown below.
Additionally exposure of bleached hair to the UV radiation of sunlight causes further damage resulting in fractures and breakage.
What can the chemical damage translate to?
- Water absorption and increased swelling during shower. Hair becomes a sponge.
- Hair dries crunchy especially at the ends
- Easy breakage and thus more flyaways
- Drier hair overall due to the removal of hair lipids during bleaching
- More styling issues such as: harder to detangle.
Note that the severity of these symptoms depends on the extent of bleaching. And this is why it is not recommended to make drastic shade changes, to do multiple bleaching sessions or to go beyond the recommended exposure time.
Important safety considerations
Side effects from bleaching are considered minimal. Most bleaching problems arise from product misuse. Things like adding the wrong peroxide strength or extending the application process can have serious consequences on your hair and skin. Overexposure can result in severe irritation to the scalp from the persulfate powder. Depending on the irritation level, some people have reported hair loss attributed to scarring alopecia, although this is in extreme cases.
However one common problem is the result of combined damage from different processes . For example, extensive sunlight exposure with chemical bleaching or chemical bleaching and permanent waving.