Scalp – chemist’s perspective

Scalp is the area of skin where hair grows. Just like all hair around the body it grows from the follicle. Just like all other skin areas - scalp is prone to various skin problems like imbalance, inflammation or other disorders.

The scalp protects the brain, not only through the hair but the whole thermal regulation, filtering out sunlight and preventing excessive heat loss in colder environments. The scalp is tightly connected to aponeurosis that covers scull’s weak connective tissue.

Scalp consists
of a superficial, low-pigment epidermis that is well protected from light by the hair and deeper dermis where the hair follicles are located. Then follows subcutaneous tissue. The capillaries in the scalp bring nourishment to the hair through the blood. Other important scalp functions are performed by the sebaceous and sweat glands, which together with sebum and sweat guarantee the protection and lubrication of both the scalp and the hair.

Each hair follicle is responsible for the function of the sebaceous glands. The specific characteristics of hair are connected sebaceous gland function and the associated hair problems may also depend on this factor. If the sebaceous glands are very active and secrete a lot of sebum, the hair will look greasy and easily covered with greasy secretions. On the other hand, if the sebaceous glands become less active and produce little sebum, the hair is dry.

The epidermis consists of four different types of cells, the most important of which, composed of keratinocytes, is divided into several overlapping rows of cells grouped into five layers; base layer, spike layer, granular layer, translucent layer (palms and soles only) and finally a roughened layer. Keratinocytes form the deepest part (base layer) and from there slowly rise towards the surface after the aging process (in about 28 days), producing a keratin protein with special resistance to external aggression (soap, oils, solvents, heat, cold, cold, light, microbes, mold, pathogens, etc.) 

The detachment of the dead cells
from the surface is usually invisible. Instead, if for some reason cell masses (hundreds or thousands of elements) form due to certain scalp problems, the detachment will appear as flakes, or dandruff. Sometimes it is difficult to tell if the scalp is dry or it has dandruff. The symptoms of both are similar, i.e. scaly and itchy scalp, although these are two different situations. The actual dandruff is caused by too much oil in the scalp. This extra oil causes skin cells to build up and come off. It is important to analyse the scalp to treat it properly to achieve a healthy scalp.

Dry scalp
is characterised by lack of moisture on the skin; this causes the scalp to become irritated and flaky. Often, if the skin on the scalp is dry, the skin on other parts of the body, such as the arms and legs, may also be dry. Dry scalp can also be caused by cold and dry air, contact dermatitis due to a reaction to products applied to the scalp (e.g. shampoo, styling gel, hairspray, etc.) or age, as the skin often dries with age. The skin cells in the scalp and body usually multiply when more are needed, after which they die and shed. Dandruff causes the skin cells in the scalp to shed faster than usual. The main cause of dandruff is seborrheic dermatitis, which makes the skin oily, red and scaly. White and yellow skin cells come off and form dandruff. Seborrheic dermatitis can occur anywhere there are sebaceous glands, incl. eyebrows and armpits. Babies have a so-called “cradle cap”.

Dandruff is often caused by a fungus called Malassezia that lives on the scalp. However, sometimes it gets out of balance and causes skin cells to multiply faster than usual. The increase in Malassezia is often due to age, hormones or stress. Dirty hair does not cause dandruff, but washing your hair too rarely can cause sebum to build up and cause skin cells to shed. 

Kaisa Leppälä
R & D Chemist (M.Sc.)