Dandruff

Dandruff

 is the shedding of dead skin cells from the scalp (not to be confused with a dry scalp). Dandruff is sometimes caused by frequent exposure to extreme heat and cold. As it is normal for skin cells to die and flake off, a small amount of flaking is normal and common and get released normally after detergent treatment. Some people, however, either chronically or as a result of certain triggers, experience an unusually large amount of flaking which can also be accompanied by redness and irritation. Most cases of dandruff can be easily treated with specialized shampoos.

The severity of dandruff may fluctuate with season as it often worsens in winter.

Those affected by dandruff find that it can cause social or self-esteem problems. Treatment may be important for both physiological and psychological reasons.

As the epidermal layer continually replaces itself, cells are pushed outward where they eventually die and flake off. In most people, these flakes of skin are too small to be visible. However, certain conditions cause cell turnover to be unusually rapid, especially in the scalp. For people with dandruff, skin cells may mature and be shed in 2–7 days, as opposed to around a month in people without dandruff. The result is that dead skin cells are shed in large, oily clumps, which appear as white or grayish patches on the scalp, skin and clothes.

                                                    .............................................................

Causes

Dandruff has been shown to be the result of three required factors:

1. Skin oil commonly referred to as sebum or sebaceous secretions.

2. The metabolic by-products of skin micro-organisms (most specifically Malassezia yeasts)

 Fungus Malassezia furfur (previously known as Pityrosporum ovale) is mostely the cause of dandruff. While this species does occur naturally on the skin surface of both healthy people and those with dandruff, in 2007 it was discovered that the responsible agent is a scalp specific fungus. During dandruff, the levels of Malassezia increase by 1.5 to 2 times its normal level.

 Malassezia globosa, that metabolizes triglycerides present in sebum by the expression of lipase, resulting in a lipid byproduct oleic acid (OA)which penetrate the top layer of the epidermis( the stratum corneum)results in an inflammatory response in susceptible persons which disturbs homeostasis and results in erratic cleavage of stratum corneum cells.

3. Individual susceptibility.

**Rarely, dandruff can be a manifestation of an allergic reaction to chemicals in hair gels, sprays, and shampoos, hair oils, or sometimes even dandruff medications like ketoconazole.
There is some evidence that excessive perspiration and climate have significant roles in the pathogenesis of dandruff.

                                                     ............................................................

Treatment

1. Salicylic acid

 Selsun Blue Naturals Dandruff Shampoo

It contains 3% salicylic acid, and salicylic acid shampoo is known to be good for acne prone scalp. It’s a great exfoliator for the scalp by removing oily residue and styling products. You can even apply this shampoo as a body wash for those back acne that come up during the summer.

2. Kairos Acne Care Solutions Shampoo

Kairos is a hair care product line made for scalp acne healing and prevention. It will help avoiding scalp acne and removes factors on the hair that might be the trigger of the condition.

It contains 0.5% concentration of salicylic acid and a cocktail of natural ingradients such as tea tree oil, apple amino acids and sapndus mukurossi which has antibacterial properties.

Do NOT use Salicylic Acid Shampoo if:

• you are allergic to any ingredient in Salicylic Acid Shampoo
• the patient is a child or teenager with the flu, chickenpox, or shingles
• the patient is younger than 2 years old

Contact your doctor or health care provider right away if any of these apply to you.

Before using Salicylic Acid Shampoo:

Some medical conditions may interact with Salicylic Acid Shampoo. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

• if you are pregnant, planning to become pregnant, or are breast-feeding
• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
• if you have allergies to medicines, foods, or other substances
• if you have had a severe allergic reaction (eg, severe rash, hives, difficulty breathing, dizziness) to aspirin or a nonsteroidal anti-inflammatory drug (NSAID) (eg, ibuprofen, naproxen, celecoxib)
• if you have liver or kidney problems, a skin infection, skin irritation, diabetes, or poor blood circulation
• if you have a history of Reye syndrome

Some MEDICINES MAY INTERACT with Salicylic Acid Shampoo. Tell your health care provider if you are taking any other medicines, especially any of the following:

• Ammonium sulfate because it may increase the risk of Salicylic Acid Shampoo's side effects
• Corticosteroids (eg, prednisone) because they may decrease Salicylic Acid Shampoo's effectiveness
• Anticoagulants, (eg, heparin, warfarin), aspirin, methotrexate, or sulfonylureas (eg, glipizide) because the risk of their side effects may be increased by Salicylic Acid Shampoo
• Phenylbutazone, probenecid, pyrazinamide, or sulfinpyrazone because their effectiveness may be decreased by Salicylic Acid Shampoo

This may not be a complete list of all interactions that may occur. Ask your health care provider if Salicylic Acid Shampoo may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

2. Coal tar

Ionil-T : Helps eliminate dandruff problems due to seborrhea and psoriasis.It appears to work by slowing down the production of skin cells, and has an anti-inflammatory effect.

 Tar helps reduce the production of skin cells, giving you a healthier looking scalp. Reduces itching and flaking. Contains the equivalent of 1% Coal Tar. For best results use at least twice a week or as directed by a physician.
Many other coal tar shampoos are available in market like Coal Tar shampoo , Polytar shampoo , T/Gel shampoo.

3. Sulfur

Sulfur is a non-metallic element, has both keratolytic and antimicrobial activity. The keratolytic effect is thought to be mediated by the reaction between the sulfur and the cysteine amino acid in the keratinocytes, whereas the antimicrobial effect may depend on the conversion of sulfur to pentathionic acid by normal flora or keratinocytes. A normal chicken egg can be used to solve dandruff utilising the sulphurous element of egg white which attracts dandruff when rubbed into the scalp.

 KAVI Sulfur Shampoo is made with colloidal sulfur to help reduce the scaling and itching associated with dandruff and seborrheic dermatitis of the scalp. Additionally, colloidal sulfur will enhance the hydrolipidic layer’s acidity and protect the scalp’s pores from acne and other bacterial infections.

Designed for daily use, the KAVI Sulfur Shampoo is easy on the senses and a practical replacement to traditional shampoos.  

4. Regulators of keratinization

  Zinc pyrithione is best known for its use in treating dandruff and seborrhoeic dermatitis. It also has antibacterial properties and is effective against many pathogens from the streptococcus and staphylococcus class.

 Some studies have shown a significant reduction in the number of yeasts after use of ZPT, which is an antifungal  agent.
 A dramatic reduction of structural abnormalities found in dandruff with the use of ZPT; the population abundance of Malassezia decreases, parakeratosis gets eliminated and corneocytes lipid inclusions are diminished.

Zinc pyrithione is approved for over-the-counter topical use in the United States as a treatment for dandruff. It is the active ingredient in several anti-dandruff shampoos such as Cedel , Pantene , Head &Sholders and Clear.                                                                                                       

                                                                                                                                            

5. Selenium sulfide

It is believed that selenium sulfide controls dandruff via its anti Malassezia effect rather than by its antiproliferative effect, although it has an effect in reducing cell turnover. It has anti-seborrheic properties as well as cytostatic effect on cells of the epidermal and follicular epithelium. The excessive oiliness after use of this agent has been reported in many patients as adverse drug effect.

Head&Shoulders and Selsun blue in market contain seleniun sulfide

6. Imidazole antifungal agents

Imidazole topical antifungals such as ketoconazole act by blocking the biosynthesis of ergosterol, the primary sterol derivative of the fungal cell membrane. Changes in membrane permeability caused by ergosterol depletion are incompatible with fungal growth and survival.
Ketoconazole is a broad spectrum, antimycotic agent that is active against both Candida and M. furfur . Of all the imidazoles, ketoconazole has become the leading contender among treatment options because of its effectiveness in treating seborrheic dermatitis as well.

Nizoral is a shampoo that contains a broad-spectrum antifungal, which inhibits the growth of yeast and other fungal infections providing relief from dandruff. Ketaconazole is also known to have anti-androgenic effects and Ketoconozole can cause a reduction in the production of testosterone and other androgens by the adrenal gland and by the male and female reproductive organs. Nizoral shampoo contains 2% Ketoconazole and is often prescribed for the treatment of fungal infections of the scalp and sebbhoreic dermatitis

 Nizoral shampoo is also unique because it's effect is long lasting. Even after rinsing, Nizoral carries on working for several days. This means that you don't need to use Nizoral every day making it extremely cost-effective. And unlike some other anti-dandruff treatments, Nizoral shampoo has a pleasant fragrance and is pH balanced leaving hair soft, healthy and clean.

7. Hydroxypyridones
In contrast to the imidazole antifungals, the hydroxypyridones do not affect sterol biosynthesis; instead they interfere with the active transport of essential macromolecule precursor, cell membrane integrity and the respiratory process of cells. Ciclopirox is widely used as an AD agent in most preparations.
 Ciclopirox Shampoo, 1%, is an antifungal indicated for the treatment of seborrheic dermatitis of the scalp in adults. Patients should be advised to avoid contact with the eyes and mucous membranes. If contact does occur, the patient should rinse thoroughly with water.
8. Naturopathic agents

There are several naturopathic agents which have been claimed to have antidandruff activity. However, in most cases, these naturopathic agents are used in combination with synthetic agents. Studies from India have shown that the herbal preparations are as effective as synthetic substances in controlling dandruff both by in vitro and in vivo studies.

9. Topsoil
The living organisms commonly found in topsoil are beneficial for controlling the production of sebum by the scalp. Mix topsoil with filtered (non chlorine) water until a mud paste the consistency of oatmeal is achieved. Apply paste directly to the scalp and allow contact for ten minutes. Application once a week will control dandruff.

10. Water temperature

Like other skin conditions, hot water can exacerbate dandruff or itching. Using slightly cooler water (not cold) during regular hair washing and rinsing has been found to reduce dandruff in some individuals.

Treatment of hair loss in women

Treatment of hair loss in women
Female hair loss treatments include minoxidil (Rogaine), hair transplants, hair powder fibers like Toppik, wigs, hair extensions, and weaves.

Minoxidil (Rogaine) is available over the counter and available in 2%, 4%, and 5% concentrations. It is marketed for women at the 2% concentration but may be used in higher strengths as directed by your doctor.
 It may be something of a nuisance to apply twice daily, but it has been shown to help conserve hair and may even grow some.
 Minoxidil tends to grow very fine small hairs wherever it is applied. It is important to avoid running the liquid onto the face or neck where it can also grow hair.

Multiple vitamins   containing zinc,vitamin C,vitamin E, vitamin B, folate, iron, and calcium is a very reasonable choice. Newer studies suggest that vitamin D may be somewhat helpful and worth considering. Specific vitamin and mineral deficiencies like iron or vitamin B12 may be diagnosed by blood tests and treated.

Biotin have been promoted for hair growth, but solid scientific studies for many of these claims are lacking.

ketoconazole (Nizoral) : Itchy scalp may cause mild, reversible hair loss.

Causes may include seborrheic dermatitis (dandruff).

 Nizoral shampoo and topical cortisone creams and lotions

 to help decrease itching.





                                                 ...........................................................

Hair transplantation  

Men who have lost their hair due to hereditary factors can no longer regain this hair through any form of treatment other than transplantation. Fortunately natural hair transplantation is now available to correct baldness.

It can also be used for women who lost some of their hair due to hereditary factors,an illness or an injury. With a good hair transplantation procedure you can grow your transplanted hair,cut it ,color it and style it.It is basically your normal hair.

                                             ................................................................

Low Level Laser Therapy

Laser Hair Therapy (LHT) is a non-surgical, scientific approch in a cosmetic treatment of hair loss , thinning hair and scalp problems. LHT has been tested for effectiveness and safety for over 30 years all around the world.  

The therapy supposedly energizes and improves blood circulation while stimulating the growth of individual hair follicles, and, as a result, produces thicker, healthier hair and combats hair loss.
In fact the hairmax laser comb has been approved by the FDA for specifically this purpose.

Treatment of hair loss

Treatment of hair loss in men

 There are thousands of unproven claims and products to help with hair regrowth. Many conditioners, shampoos, vitamins, and other products claim to help hair grow in some unspecified way. Nioxin has been a popular brand of shampoo for hair loss, but there is no definite evidence showing it is any more effective than regular shampoos.
These products are usually harmless but generally not scientifically proven and therefore potentially useless.

To slow down hair loss, there are at least four potentially effective, basic options. These include medications like Minoxidil, Propecia,  Avodart and ketoconazole shampoo which are maintenance-type medications and are for long-term use. Stopping these drugs does not seem to worsen or exacerbate the prior hair loss. In other words, stopping the medication will not leave you worse than you started out prior to the medication.

Minoxidil (Rogaine): This topical medication is available over the counter and no prescription is required. It can be used in men and women.
Minoxidil (Rogaine) is a vasodilator originally used as an oral drug (Loniten) to treat high blood pressure. However, minoxidil was discovered to have the side effect of hair growth and reversing baldness.
It acts  by widening blood vessels and opening potassium channels, it allows more oxygen, blood and nutrients to the follicle. This can also cause follicles in the telogen phase to shed, usually soon to be replaced by new, thicker hairs.

 Consequently, in the 1980s, Upjohn Corporation received FDA approval to market a topical solution that contained 2%, 4% solution, an extra-strength 5% solution, and a new foam or mousse preparation.
Objective evidence shows that minoxidil is effective for treatment of male-pattern hair loss in both the frontal areas and the vertex area of the scalp. At the conclusion of a 48 week study.

 Minoxidil needs to be applied regularly (once or twice daily) for hair gained to be maintained.

Finasteride (Propecia): This medication is FDA approved for use in only men with androgenic hair loss. Although not FDA approved in women, it has been used "off label" in women with androgenic hair loss who are not pregnant or planning to become pregnant while on the medication.
. Propecia is a lower-dose version of a commercially available drug called Proscar that helps shrink enlarged prostates in middle-aged and older men.

 Finasteride is in a class of medications called 5-alpha reductase inhibitors,the enzyme responsible for the conversion of free testosterone to DHT.
It acts by blocking the action of natural hormones in scalp hair follicles.
Propecia 1 mg tablets are available by prescription and taken once daily.
Propecia may grow and thicken hair to some extent for some people, but its main use is to keep (maintain) hair that's still there. Studies have shown that this medication works well in some types of hair loss and must be used for about six to 12 months before full effects are determined.
 Possible but very unlikely side effects include impotence or a decreased sex drive (libido). Studies have shown that these side effects were possibly slightly more common than seen in the general population and are reversible when the drug is stopped.

Dutasteride (Avodart) has recently been used as "off label" to treat hair loss in men.Although not FDA approved in women, it has been used "off-label" in women with androgenic hair loss who are not pregnant or planning to become pregnant while taking the medication.
Dutasteride is similar to finasteride (Propecia, Proscar) and is in a class of medications called 5-alpha reductase inhibitors.
It acts by blocking the production or binding of a natural substance in the scalp hair follicles.
Dutasteride is available as soft capsules in market.
It is to be taken at both 0.5 mg and 2.5 mg/day generated a superior hair count to finasteride 5 mg at 12 and 24 weeks.
Touching the contents of the capsules may potentially harm a male fetus and females who accidentally touch leaking capsules should wash the area with soap and water immediately.
There is a six-month clearance time required after taking this medication before being permitted to donate blood.

Ketoconazole shampoo (Nizoral)

Some preliminary research suggests that ketoconazole shampoo may possibly be beneficial in men suffering from androgenic alopecia. Support for this comes primarily from one study in 1998 that compared ketoconazole 2% to the proven hair loss drug minoxidil 2% in men with androgenic alopecia.
It acts by improving hair density and size and proportion of anagen follicles.
Ketoconazole shampoo is only FDA approved for the treatment of dandruff and seborrheic dermatitis of the scalp, so although ketoconazole may possibly be useful as a hair loss remedy, the FDA does not accept that there is enough evidence to endorse or market it as one to the general public.

hair loss

About Baldness

When there’s no hair to cover the head, you have a condition called baldness. For most baldness, it’s hereditary. Called Androgenetic Alopecia, patterned baldness strikes both sexes and usually result in thinning or hair loss in the crown or vertex area of the scalp or a receding top hairline, or both. Women often suffer a more even or homogenous hair loss affecting not just the crown but a general thinning of hair.

Hair loss in men

Androgenetic alopecia or more commonly known as male pattern baldness (MPB) afflicts almost half of the men on this planet. It’s part of the aging process but it strikes young people as early as the early 20s or even late teens because of their genetic predisposition to it.

What Cause Hair Loss In Men?

• Androgenetic Alopecia - The most common cause accounting for 95% of all known hair loss cases, its name comes from the male androgen hormone, testosterone that gets converted into DHT by the action of the 5-alpha-reductase enzyme. Once they get to the scalp and binds with the hair follicles, you can kiss your beautiful hair styles goodbye.The predisposition to it is hereditary and progressive alopecia can only be managed, not cured.

• Chemotherapy and Medication - Some chemicals are so potent that within 24 hours of taking them, hair starts to fall off.  Cancer patients are counseled on this when undertaking chemotherapy and often use wigs or have their head shaved even before chemotherapy starts.  But once chemotherapy is stopped, hair growth resumes in a few months though not always in the same density levels.

• Ailments and Infections - Blood disorders like anemia can deprive hair follicles of the nutrients to grow hair. Skin infections like lichen planus can cause patchy hair loss. Thyroid disorders that result in Thyroxin deficiency or overproduction that leads hair loss. But once the ailment or infection is treated, hair growth resumes usually in 3-4 months after being cured.

• Nutritional Deficiency - Hair is 100% keratin, a protein byproduct. Insufficient protein can lead to hair loss as there’d be no keratin to produce hair with. Vitamin and mineral deficiency leads to all sorts of health problems including hair loss. An entire book can be written to discuss the role of vitamins to the body and in maintaining hair growth. Just read about it online.

Hair loss in women

Androgenetic alopecia is not exclusive to men and can strike the fairer sex as well; though in lesser numbers.  Female pattern baldness is likewise hereditary but more commonly carries a lesser incidence of receding hairline or balding crown common in men.  

Instead, women suffer a more diffuse hair thinning or evenly spread over the scalp while retaining their frontal hairlines. It is also more gradual and is often seasonal caused by hormonal changes, medication and stress and can reverse themselves once these conditions are gone.

What Causes Hair Loss in Women?

• Androgenetic Alopecia – Patterned hair loss common in men can also be found in women but with a more diffused hair thinning.   Women with the same hereditary patterned hair loss will often lose hair at the sides and crown but maintain their front hairline and rarely suffer complete baldness.

• Hormonal changes – Women suffer more cyclical changes in hormonal concentration that is often attributed to birth control, pregnancy and menopause. Most common of these is pregnancy as this causes hormonal imbalance that can upset follicular activity.  Contraceptives also upset hormonal balance to cause the same hair loss problems.

• Aging – Diffuse hair loss is most prevalent after menopause.

• Chemotherapy and Medication – Hair loss due to chemotherapy is almost instant and can be complete with a week of treatment. Some form of potent prescribed medication against certain illness like thyroid medication, cholesterol lowering, high blood medication such as beta-blockers and “mood” medication such as Prozac and anti-depressants can also cause diffuse hair loss.

• Hair Styling -  Braiding, dreadnaughts and other hair styles that cause severe stress to hair roots can cause hair loss.  This also include frequent use of strong hair styling products like hair sprays, strong cleansing shampoos that dry the hair and scalp as well as dying and bleaching.

• Crash Diets – Sudden nutritional deprivation caused by crash diets over prolonged periods can stave hair follicles to stunt normal hair production.

• Scalp Infestation – Localized hair loss in patches caused by scalp inflammation in lichen planus infestation can permanently damage follicles in different scalp area.
  

Patchy hair loss

Patchy hair loss

Some conditions produce small areas of hair loss, while others affect large areas of the scalp. Common causes of patchy hair loss are

Androgenetic alopecia is not exclusive to men and can strike the fairer sex as well; though in lesser numbers.  Female pattern baldness is likewise hereditary but more commonly carries a lesser incidence of receding hairline or balding crown common in men.  

• alopecia areata (small circular or coin size patches of scalp baldness that usually grow back within months),
• traction alopecia (thinning from tight braids or ponytails),
• trichotillomania (the habit of twisting or pulling hair out),
• and tinea capitis (fungal infection).

What is alopecia areata?

A common condition, alopecia areata usually starts as a single quarter-sized circle of perfectly smooth baldness. Alopecia patches usually regrow in three to six months without treatment. Sometimes, hair grows back in white. In another variant, alopecia can produce two or three bald patches. When these grow back, they may be replaced by others. The most extensive form is called alopecia totalis, in which the entire scalp goes bald. It's important to emphasize that patients who have localized hair loss generally don't go on to lose hair all over the scalp. Alopecia can affect hair on other parts of the body, too -- for example, the beard or eyebrow.

Alopecia areata is generally considered an autoimmune condition, in which the body attacks itself (in this case its own hair follicles). Most alopecia patients, however, do not have systemic problems and need no medical tests. While alopecia areata has frequently been blamed on "stress," in fact, it may be the other way around; that is, having alopecia may cause stress.

Treatments for alopecia areata :                                                                                 include injecting small amounts of steroids like triamcinolone into affected patches to stimulate hair growth. Although localized injections may not be practical for large areas, often this is a very effective treatment in helping the hairs return sooner.                                                    Other treatments such as oral steroids, immunosuppressives, or ultraviolet light therapy are available for more widespread or severe cases but may be impractical for some because of potential side effects or risks.                                                                                         In most mild cases, patients can easily cover up or comb over the affected areas. In more severe and chronic cases, some patients wear hairpieces; nowadays, some men shave their whole scalp now that this look has become fashionable.

What is traction alopecia?

This is a small or localized hair loss area caused by repetitive or persistent pulling or force on hair roots. Tight braids and ponytails can pull hard enough on hairs to make them fall out. If this happens, it's best to choose hairstyles that put less pressure on hair roots. The sooner this is done the better to avoid permanent damage.

What is trichotillomania?

This refers to the habit of someone voluntarily pulling at their own hairs or twisting them, sometimes without realizing it. The scalp and eyelashes are often affected. Unlike alopecia areata patches, which are perfectly smooth, hair patches in trichotillomania show broken-off hairs. Treatment is often entirely behavioral:                                                                           You have to notice that you're doing it and then consciously stop. Severe or resistant cases may require stress counseling with a therapist or psychologist or medical treatment with a psychiatrist. Several antidepressant or anxiety medications have been shown to potentially help with this condition.

What is tinea capitis?

Tinea is the medical word for fungal infection, and capitis means head. Tinea capitis is fungal infection of the scalp that for the most part affects school-age children. Tinea capitis is more common in black African or African-American scalps. This condition is rare in healthy adults. Bald spots usually show broken-off hairs. Oral antifungals are needed to penetrate the hair roots and cure the infection after which hair grows back. It is contagious from sharing hats or combs and brushes.

Prevention of hair loss

Preventing hair loss can be just a matter of maintaining proper nutrition, exercise and body hygiene with emphasis on scalp hygiene as well as using gentler chemicals in hair styling as well as sporting a more relaxed natural hair styles. Hereditary patterned alopecia is genetic in nature and cannot be prevented, only controlled or delayed with any number of OTC cosmetic and pharmaceuticals in the market.

Hair description

Description  
Construction of the root and strand.
                                                                                                                                                              
 is a filamentous biomaterial, that grows from follicles found in the dermis. The human body, apart from its glabrous skin, is covered in follicles which produce thick terminal and fine vellus hair. Most common interest in hair is focused on hair growth, hair types and hair care, but hair is also an important biomaterial primarily composed of protein, notably keratin.

 Hair growth begins inside the hair follicle. The only "living" portion of the hair is found in the follicle. The hair that is visible is the hair shaft, which exhibits no biochemical activity and is considered "dead".The base of the root is called the bulb, which contains the cells that produce the hair shaft.Other structures of the hair follicle include the oil producing sebaceous gland which lubricates the hair and the erector pili muscles, which are responsible for causing hairs to stand-up. In humans, with little body hair, the effect results in goose bumps.

Each strand of hair is made up of the medulla, cortex, and cuticle.The innermost region, the medulla, is not always present and is an open, unstructured region. The highly structured and organized cortex, or middle layer of the hair, is the primary source of mechanical strength and water uptake. The cortex contains melanin, which colors the fiber based on the number, distribution and types of melanin granules. The shape of the follicle determines the shape of the cortex, and the shape of the fiber is related to how straight or curly the hair is.  

   Hair pigment

All natural hair colors are the result of two types of hair pigment. Both of these pigments are melanin types, produced inside the hair follicle and packed into granules found in the fibers. Eumelanin is the dominant pigment in dark-blond, brown, and black hair, while pheomelanin is dominant in red hair. Blond hair is the result of having little pigmentation in the hair strand. Gray hair occurs when melanin decreases or disappears

Human hair growth

Hair grows everywhere on the external body except for mucus membranes and glabrous skin, such as that found on the soles of the hands, feet, and lips.
Hair follows a specific growth cycle with three distinct and concurrent phases: anagen, catagen, and telogen phases. Each phase has specific characteristics that determine the length of the hair. All three phases occur simultaneously; one strand of hair may be in the anagen phase, while another is in the telogen phase.
The body has different types of hair, including vellus hair and androgenic hair, each with its own type of cellular construction. The different construction gives the hair unique characteristics, serving specific purposes, mainly warmth and protect.

Eyebrows and eyelashes.

The eyebrows are situated above the eyelids on the forehead. In many other mammals they contain much longer hairs that are upright, functioning as tactile sensors. While they have little significance to the survival of humans, they remain a part of the body's physiological makeup because of the role they play in protecting the eyes from dirt, sweat, and rain, as well as non-verbal communication.

Straight hair

According to the recent single origin hypothesis, anatomically modern humans arose in East Africa approximately 200,000 years ago (Tishkoff, 1996). Then, ~150,000 years later, modern humans began to expand their range to regions outside of (and within) this continent (Tishkoff, 1996). The skin of those in the group that left the African continent had developed the ability to manufacture vitamin D (which was essential for bone development) upon exposure to UV light.However, the UV light of northern regions was too weak to penetrate the highly pigmented skin of the initial migrants in order to provide enough vitamin D for healthy bone developmen.

In this sense, the evidence with regard to the evolution of straight hair texture seems to support Jablonski's suggestions ^[28] that the need for vitamin D triggered the transition back from dark to light skin.
This argument is made based on the principle that straight fibers better facilitate the passage of UV light into the body relative to curly hair. It is substantiated by Iyengar's (1998) findings that UV light can pass through straight human hair roots in a manner similar to the way that light passes through fiber optic tubes (Iyengar, 1998).Nonetheless, some argue against this stance because straighter hair ends tend to point downward while fiber optics requires that light be transmitted at a high angle to the normal of the inner reflective surface. In light of this, they suggest that only light reflected from the ground could successfully enter the hair follicle and be transmitted down the shaft