Friday, October 31

Vellus hair definition - What is vellus hair?

   ›      ›   What is vellus hair and its definition.

What is vellus hair?

Vellus hair, colloquially also known as 'peach fuzz', is fine and short strand growing on the body right from childhood. Vellus strands, lacking melanin, are usually unpigmented, light-colored and nearly transparent.
Peach fuzz typically refers to the light colored short hair found on the upper lip of young preadolescent boys. Three types of hairs are present in the human body, namely lanugo, vellus and terminal types. The soft strands can be clearly distinguished from terminal type, which is darker, thicker and longer. It can also be distinguished from lanugo type found on fetus. The lanugo is thicker and longer. The fetus sheds lanugo at 30-36 weeks to be replaced by vellus type. In premature babies lanugo may be seen at birth.

The number of vellus follicles and their distribution in the body are predetermined genetically. Its transformation into terminal type is governed by the gender of the individual, puberty and androgen hormones input. During puberty increase in androgenic hormones cause them to convert into terminal ones in the axillary and pubic areas. During the transition to terminal type, intermediate type of strands can be seen. The soft, light strand's length usually does not exceed 2 mm. due to very short anagen phase.
Vellus hair

Vellus follicles, unlike the terminal follicles, do not connect to sebaceous glands. In children, excluding scalp, eyebrows and eyelashes, the body hair is predominantly soft and short. Vellus is very much apparent is children and women. In men they get reduced due to their transformation into terminal ones, whose presence also obscures the presence of those remaining strands. The vellus strands have many functions such as, body insulation, temperature regulation by aiding sweat evaporation and aiding in the perception of touch sensation.
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Web definition of vellus hair
Definition by thefreedictionary.com: "Short, fine, usually nonpigmented which covers much of the body."
Definition by yourdictionary.com: "Short, fine, light-colored, and barely noticeable hair that develops on most of a person's body from his/her childhood."
Definition by collinsdictionary.com: "short fine unpigmented hair covering the human body."
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Medical conditions involving vellus hair

Accelerated vellus syndrome means a condition wherein the anagen phase of the soft, short strands is extended and accelerated. In this accelerated syndrome the slender light colored downy strands gain length. Accelerated syndrome may occur due certain medications as well as abnormal hormonal activity in postmenopausal women and transgender patients.
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In women with polycystic ovarian syndrome, accelerated syndrome may appear which subsequently convert them into terminal types. This accelerated syndrome is also seen with abundance of vellus as a side effect of diseases like Cushing's syndrome and anorexia nervosa. In male pattern baldness, the bald area is not hairless. The growth of thick, dark terminal strands slow down and the light-colored short vellus strands takeover and cover the bald area.
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Reference:
1.Lacarrubba F, Micali G, Tosti A. Absence of vellus in the hairline: a videodermatoscopic feature of frontal fibrosing alopecia. Br J Dermatol. 2013 Aug;169(2):473-4. doi: 10.1111/bjd.12316.
2.Vogt A, Hadam S, Heiderhoff M, Audring H, Lademann J, Sterry W, Blume-Peytavi U. Morphometry of human terminal and vellus follicles. Exp Dermatol. 2007 Nov;16(11):946-50.

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Image source: http://en.wikipedia.org/wiki/File:Huid.jpg
Author: Svdmolen | License: CC BY-SA 3.0
Current topic in natural skin care: What is vellus hair and its definition.
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Friday, October 24

Hypertrichosis treatment - Hypertrichosis management

› › › Hypertrichosis treatment - Hypertrichosis management.
Hypertrichosis is excessive growth of hair on any part of the body. Hypertrichosis excludes androgen-induced excessive hair growth, known as hirsutism. Acquired hypertrichosis can be treated by removing the underlying cause.
For congenital hypertrichosis there is no cure. Hair removal treatments are the best options for improving the appearance. In patients with localized hypertrichosis, satisfactory results can be realized with the treatment. In extensive and generalized forms, hair removal treatment is time consuming and likely to be unsatisfactory.

In acquired form of hypertrichosis cases, the treatment of the underlying causative factor can normalize the hair growth. However alleviating or completely resolving the medical cause may take considerable time. Till such time temporary cosmetic treatment to remove the unwanted hair is necessary for addressing the associated emotional problems of the patient. However it is to be noted that, in some cases the hair removal methods may cause, dermatitis, hives or scarring.

Hypertrichosis treatment and management

Extensive hypertrichosis may cause cosmetic embarrassment and is psychologically devastating to the patient. Generalized hypertrichosis may involve all three types of hairs, namely, lanugo, vellus and terminal hairs. In localized hypertrichosis, the local vellus hairs transform into terminal hairs.

Temporary hair removal for hypertrichosis

There are many methods of temporary removal of hair. In these methods as the hair follicle is not destroyed, new strands grow after some time. Skin sensitivity, hives, scarring, ingrown hair (pseudofolliculitis), folliculitis, dermatitis, hyperpigmentation and hypopigmentation are the possible problems associated with these methods. It is cumbersome and time consuming for treating large areas of hypertrichosis.

Superficial removal

Abrasives like pumice stones are rubbed on the skin to break and remove hair. Quite often this method damages the skin. Shaving cuts and removes the hair at the skin level. The hair may become apparent after two or three days of growth. Chemical depilatories are available in gel and cream forms. They contain calcium thioglycolate or potassium thioglycolate.
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These chemicals react with the cystine and breaks down the disulfide bonds in keratin. The weakened hair can be just scraped off. In all these superficial methods removal of hypertrichosis condition is highly temporary and chemicals may sensitize the skin.

Depilation

In epilation, hair is completely removed from the hair shaft. It is quite an effective method for temporary removal of hypertrichosis. Each hair may be pulled out individually with a tweezer. By threading also a small group of hairs can be removed at a time. Waxing treatment is done to remove large numbers in one go. As an alternative to waxing, sugaring used. Sugar and lemon juice are heated in water and made into paste. The paste is applied to the skin and a cotton strip is placed over it. The cotton strip is pulled back sharply to pull out the strands stuck on it from the follicle.

Hair growth inhibition in hypertrichosis

Eflornithine cream (Vaniqa cream 13.9%) is successfully used for reducing the unwanted hair. Eflornithine interferes with ornithine decarboxylase. Ornithine decarboxylase is needed in the follicles for hair growth. Eflornithine irreversibly binds to Ornithine decarboxylase and prevents the natural substrate ornithine from accessing the active site of the enzyme. The treatment effects become apparent after 4-8 weeks of application. However hypertrichosis condition returns in eight weeks when the application is stopped.

Permanent hair removal for hypertrichosis

For permanent reduction in hair use of electrolysis and laser technology are the best solutions. Skilled persons are required for carrying out these procedures. Many sittings may be required to reduce hair growth and get satisfactory results. The results of hypertrichosis treatment depend upon the skill of the technician and and use of correct intensity and duration of current.

Electrolysis for hypertrichosis

Electrolysis is aimed to destroy the hair follicle and bulb for successful hair removal. A fine needle is inserted into the hair follicle and a weak electrical current is applied to destroy bulb. There are two types of electrolysis. In galvanic electrolysis direct current is used to destroy the hair bulb. In thermolysis a high frequency alternating current is used to produce heat and cauterize the hair bulb. Hypertrichosis treatments are also offered combining the two procedures.
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Each electrolysis session may extend up to 30 minutes and a number of sittings may be required. Post inflammatory hypopigmentation and hyperpigmentation are common with electrolysis treatment for hypertrichosis. There may be erythema, folliculitis and angioedema at the site of electrolysis. Up to 50% regrowth may be observed after the procedure requiring further sessions.

Laser-assisted hair reduction in hypertrichosis

In laser hair removal, exposure to pulses of laser light destroys the hair follicle by selective photothermolysis. The Food and Drug Administration (FDA) has approved hair removal lasers for "permanent hair reduction". The laser procedure is effective on pigmented terminal hair. Hypertrichosis with lanugo or vellus hairs may not respond to the treatment. In laser-assisted hair reduction side effects like erythema and perifollicular edema are common. In some cases there may be crusting, blistering, hyperpigmentation and hypopigmentation. These side effects are mostly temporary and resolve with skin care measures.
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Reference:
1.Trueb RM. Causes and management of hypertrichosis. Am J Clin Dermatol. 2002;3(9):617-27.
2.Trueb RM. Hypertrichosis. Hautarzt. 2008 Apr;59(4):325-37; quiz 338.
3.Goel N, Rajaram S, Gupta B, Gupta K. Familial congenital generalized hypertrichosis. Indian J Dermatol Venereol Leprol 2013;79:849.

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Current topic in dynamic skin care: Hypertrichosis treatment.
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Monday, October 13

Melanocytes function

What are the functions of melanocytes?

The classic melanocytes function is melanin pigment synthesis.
The non-classical, non-cutaneous melanocytes dispersed across the body carry out a variety of functions depending on their locations. They may retain common lineage signature function of melanin pigment synthesis. The type of melanin pigment (eumelanin or pheomelanin) produced and their relative proportion in the skin decides one's skin color.

Melanocyte precursors cells differentiate and migrate from the neural crest via the mesenchyme into the epidermis and hair follicles. Classical melanocytes are pigment producing cells, which are found in the dermis, epidermis and hair follicles. During development they follow the dorsolateral migratory pathway. Nonclassical melanocytes migrate to several non-cutaneous sites. Interacting continuously with the surrounding tissues, they makeup local populations having different functions. The non-cutaneous sites include eyes, inner ear, brain, leptomeninges and heart.

Classical melanocytes functions

In many species of animals the melanocytes have evolved to provide camouflage from prey and predators. In humans, protection against UV radiation has evolved as one of the primary functions of the pigment producing cells. Skin pigmentation, being the most apparent display of human polymorphic traits, defines ethnicity and race.
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UV radiation causes cellular damage and DNA damage. The cap-like melanin pigment accumulation above the nucleus of the keratinocyte, protects the nucleus from the DNA damage. The antioxidative and redox signaling activity during of the melanogenesis process neutralizes the harmful free radicals in the skin. The hair color is also due to the pigment deposit in the hair shaft. Grey hair appears when the melanocytes in the hair follicle stop producing and depositing melanin.
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The highly reactive quinone intermediates produced during melanogenesis have antibacterial and antifungal properties. The post inflammatory hyperpigmentation by the melanocytes dampens the inflammatory response and suppresses inflammation. They also interact with Langerhans cells and regulate skin immune response.

Nonclassical melanocytes functions

The presence of the melanocytes and melanin is necessary for the proper functioning of inner ear, eyes, heart and brain.

Melanocytes function in eyes

Pigment cells are found in retinal pigment epithelium (RPE) and uveal tract in the eyes.

RPE
RPE melanin is essential for the development of neural retina. RPE cells are thought to produce melanosomes only during the prenatal period. RPE melanin protects the neural retina from reactive oxygen species and macular degeneration. RPE also provides visual acuity.
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Uveal melanocytes
The uvea, the middle layer of eye, is divided into choroid, ciliary body and iris. All the three parts have pigment cells. The pigment cells of the iris impart the eye color to an individual. The pigment in the choroid is believed to protect the cells from oxidative damage by free radicals.

Functions of melanocytes of the inner ear

The pigment producing cells are found in the cochlea and the vestibular organ. The lack of these cells or lack of inner ear melanocyte function can lead to deafness.
Cochlear melanocytes are present within the stria vascularis and the modiolus. They are essential for the proper development and function of cochlea.
The vestibular labyrinth of the inner ear also has pigment cells. It is believed that they may be associated with balance perception.

The melanocytes of the heart

These group of cells are found in the valves and septa of the heart. Cardiac pigment cells, though appear not essential for heart activity, are found to trigger atrial arrhythmia. They may be regulating Ca levels and redox signaling.

Functions of the melanocytes of the brain

These cells are found in the sympathetic cephalic ganglia and leptomeninges. The melanocytes are also found along cerebral capillaries. The ventrolateral surfaces of the medulla oblongata are covered by the pigment cells. Endocrine and redox activity are attributed to these cells. The pigment present is brain-specific neuromelanin.
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Reference:
1.Tsatmali M, Ancans J, Thody AJ. Melanocyte function and its control by melanocortin peptides. J Histochem Cytochem. 2002 Feb;50(2):125-33.
2.Gertrude-E. Costin, Vincent J. Hearing. Human skin pigmentation: melanocytes modulate skin color in response to stress. The FASEB Journal vol. 21 no. 4 976-994.

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Current topic in dynamic skin care: Melanocytes function.
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